Parasite Control

7 Reasons Your Deworming Program Isn’t Working

Tue, 12 May 2026 18:09:15 GMT

For many producers, deworming has become a routine part of herd management. Cattle are processed, products are administered and the expectation is that parasite control is handled for another season.

But across the industry, cattle continue to underperform despite regular treatment. In many cases, the issue is not a single product failure, but a combination of resistance pressure, hidden production losses and management habits that gradually reduce the effectiveness of parasite control programs over time.

On the most recent episode of “ The Bovine Vet Podcast ,” Megan Bollin, a technical services veterinarian with Norbrook, and Nancy Jackson, a field veterinarian for the Mississippi Board of Animal Health, outlined several reasons why deworming programs may not be delivering the results producers expect.

1. Subclinical Parasites May Be Hurting Performance Before You Notice

Parasites do not need to cause obvious disease to affect productivity. In many cases, the biggest losses are occurring quietly through reduced digestion, feed efficiency and weight gain.

“Those parasites are going in and doing damage to the lining of the abomasum, and so what normally should be a lower pH is actually becoming more neutral. That impacts protein digestion, nutrient absorption and even appetite. It reduces voluntary feed intake, and then that cascades into average daily gain, feed efficiency, milk production and reproductive performance,” Bollin explains.

Because those effects develop gradually, they are often difficult to recognize without measurement.

“They’re those silent robbers that are there. We can’t really see them, and that’s why it’s called a subclinical impact, but they’re doing major damage,” Bollin says.

Jackson notes some calves may visibly underperform, but many losses remain subtle enough that producers underestimate the impact.

“You can see it in some cases, calves just standing there, not grazing, not performing, but a lot of times producers don’t realize what they’ve lost because they’re not measuring it,” Jackson says.

2. Resistance Is Already Present on Many Operations

Reduced dewormer efficacy is no longer considered a future concern. Parasite susceptibility can now vary significantly between farms, even within the same geographic region.

“Even from one side of the county to the other, recommendations might be very different depending on pasture type, parasite exposure and treatment history,” Bollin says.

That variability makes it increasingly difficult to assume a protocol that works well on one operation will perform the same way elsewhere.

At the same time, few replacement products are expected in the near future.

“We’ve routinely given the same things over and over, and we don’t have any new molecules on the horizon,” Bollin explains.

As resistance pressure increases, reduced efficacy in existing products can have growing consequences for cattle performance and long-term parasite control.

3. You May Be Underdosing More Often Than You Think

One of the most common management issues contributing to reduced efficacy is underdosing. As cattle size has increased over time, dose estimates have not always kept pace.

“Our producers still think they have a 1,000-lb. cow, but cows have been getting bigger for years. So, we’ve probably been underdosing cattle, especially those larger animals and bulls.” Jackson warns.

Underdosing exposes parasites to a drug without fully eliminating them, increasing the likelihood that surviving worms contributes to future resistance problems.

4. Some Dewormers Are Being Used Like Fly Control Products

Convenience can also create problems when products are used outside their intended purpose.

According to Jackson, some producers are administering pour-on dewormers at partial doses primarily for fly control rather than at labeled doses intended to control internal parasites. Repeated exposure to subtherapeutic drug levels creates ideal conditions for resistant parasites to survive and spread.

5. Poor Record-Keeping Makes Resistance Harder to Detect

Inconsistent product tracking can make parasite control decisions much more difficult over time. Without knowing which active ingredients or drug classes have been used previously, producers may unknowingly rely on the same class repeatedly or struggle to evaluate whether a protocol is still effective.

“I’ll ask what they used, and they’ll say, ‘It was the blue one’ or ‘I got it off the shelf at the co-op.’ But we need to know the active ingredient to make good decisions,” Jackson says.

That lack of detail can make it harder to identify emerging resistance patterns before they become more significant problems.

6. Application Problems Can Look Like Resistance

Not every apparent treatment failure is true resistance. In some cases, the problem lies in how the product was administered.

“There are a lot of things that have to go right with a pour-on for it to work. If the animal is dirty, that product isn’t going to get absorbed. If it rains, it can dilute it. Oral products can be spit out. There are a lot of factors that can look like resistance but aren’t,” Bollin explains.

Without recognizing those factors, producers may incorrectly conclude that resistance is solely to blame.

7. Parasite Problems Don’t Stay on One Farm

The effects of ineffective parasite control can extend well beyond a single operation. As calves move through the production chain, resistant parasite populations can move with them, affecting downstream performance and management decisions.

“When those calves leave your place, you’re passing that parasite load on to someone else. If it’s resistant, it affects the feedlot and performance down the line,” Jackson warns.

That interconnectedness means small failures repeated across multiple operations can gradually reshape parasite pressure across the industry.

Why Parasite Problems Keep Building

Many deworming programs do not fail because of one dramatic mistake. Instead, they lose effectiveness gradually through repeated small issues: underdosing, inconsistent application, misuse of products and resistance pressure that goes unnoticed until performance has already been affected.

Routine treatment schedules alone are no longer guaranteeing consistent outcomes, particularly when the surrounding management practices remain inconsistent. This means parasite control is becoming less about whether cattle are treated and more about how those treatments are being used and how the results are being monitored over time.

To hear more from Bollin and Jackson on how deworming strategies may be falling short, and how strategies are evolving, listen to the full conversation on the latest episode of “The Bovine Vet Podcast.”

The New Rules of Parasite Control

Thu, 07 May 2026 19:35:29 GMT

For decades, parasite control in cattle has followed a familiar script: Treat the whole herd in the spring, treat again in the fall and trust that the job is done. It’s simple, efficient and deeply ingrained in how many operations function.

But that approach is starting to shift.

On the most recent episode of “ The Bovine Vet Podcast ,” Megan Bollin, a technical services veterinarian with Norbrook, and Nancy Jackson, a field veterinarian for the Mississippi Board of Animal Health, describe an industry moving away from routine, whole-herd deworming and toward a more strategic, data-driven approach.

At the center of that shift is a fundamental change in thinking. As Bollin explains, the goal is no longer the complete elimination of parasites but rather smarter management of them.

“Historically, we’ve had the mindset of just getting rid of all the parasites, right? One-hundred percent — we want them all gone. But we’ve got to consider that 90% of the life cycle is in the pasture. So we’ve got to learn to live with these parasites,” Bollin says.

Why Routine Deworming Falls Short

Routine deworming became standard for a reason. It aligned with when cattle were already being handled, minimized labor and offered a straightforward protocol producers could repeat year after year. The problem is that convenience doesn’t always align with biology. Treating cattle when they are easiest to handle may not coincide with the most effective point in the parasite life cycle, which ultimately limits the return on treatment.

“It may be a convenient time when we have them caught, and I know it takes a lot of labor and planning and resources to get those animals through the chute and treat them, but it may not be the most economically beneficial time to treat them if we’re not applying that product at the correct time in the life cycle,” Bollin says.

Because most of the parasite life cycle occurs on pasture rather than in the animal, poorly timed treatments can miss the window where they would have the greatest impact. The result is a system that feels consistent but may not be working as efficiently as intended.

Replacing Guesswork With Diagnostics

As parasite control becomes more strategic, diagnostics are moving from optional to essential. Instead of relying on assumptions or visible signs, producers are increasingly being encouraged to measure parasite burden directly.

Fecal egg count testing provides a snapshot of parasite burden by quantifying the number of parasite eggs present in a manure sample, giving a measurable baseline rather than relying on assumption. Building on that, the fecal egg count reduction test (FECRT) evaluates how well a dewormer is working by comparing egg counts before and after treatment — typically 10 to 14 days later — to determine the percentage reduction. A reduction of around 95% is generally considered indicative of effective treatment, while lower reductions may signal reduced efficacy or emerging resistance.

Together, these tools allow parasite control decisions to be based on data, helping tailor treatment strategies to the specific conditions of each herd rather than applying a one-size-fits-all approach.

“If you’re doing just a straight fecal egg count, it needs to be quantitative. A qualitative test — just saying whether parasites are there or not — is not helpful, because you’re always going to have parasites,” Bollin advises.

Those baseline measurements allow for informed decisions about whether treatment is needed and how well products are performing. Follow-up testing is just as important, helping confirm whether a dewormer is still effective.

Rather than relying on routine schedules, this approach acknowledges that treatment decisions vary from one operation to the next.

“There’s no magic number that says you need to treat at this high of an egg count,” Bollin says. “It’s going to depend on your geography, your herd and your operation.”

That variability is something producers already manage in other aspects of their operation. As Jackson notes, parasite control should be approached with the same level of flexibility.

“Every farm is unique — when they calve, when they wean — so it’s hard to make a cookie-cutter template,” Jackson says.

In many cases, the need for measurement comes down to what isn’t immediately visible. Subclinical parasite burdens can quietly reduce performance without obvious warning signs, making data even more valuable.

Refugia: A Counterintuitive but Critical Strategy

Rather than treating every animal, every time, the concept of refugia encourages leaving a portion of the parasite population unexposed to dewormers. Bollin explains that this approach helps preserve drug effectiveness by maintaining a population of parasites that remain susceptible, rather than selecting only for those that survive treatment.

“Refugia is leaving a percentage of the parasites unexposed to a dewormer. The idea is that resistance is a heritable trait, so we’re trying to dilute those resistance genes and maintain a population of parasites that are still susceptible to the products we have available,” Bollin says.

While it may seem counterintuitive, this strategy reflects a broader shift away from trying to eliminate parasites entirely and toward managing them in a way that sustains long-term control.

Implementing refugia doesn’t mean abandoning treatment. Instead, it means focusing on the animals that benefit most.

“We know that calves are going to be more susceptible, so ideally we want to treat those animals. But those mature cows — if they’re in good condition and have good nutrition — their immune system should be able to suppress those parasites,” Bollin says.

This kind of targeted approach allows producers to use dewormers more effectively while also supporting broader parasite management goals.

Combining Classes to Improve Efficacy

While refugia focuses on preserving a population of susceptible parasites, another strategy aims to improve how effectively treated parasites are eliminated. Combination deworming, or the concurrent administration of anthelmintics from different drug classes, is increasingly being used to improve efficacy in the face of variable parasite susceptibility.

Because these classes act through distinct mechanisms — such as macrocyclic lactones targeting parasite neuromuscular function and benzimidazoles disrupting microtubule formation — using them together can increase overall parasite kill and reduce the proportion of resistant survivors. The benefit becomes clear when considering how efficacy compounds across treatments.

“If you have 100 worms and you go in with a product that has 80% efficacy, you’re left with 20. Then you come in with a second dewormer, also at 80% efficacy, and it kills 80% of those 20. So you go from 80% efficacy up to 96% by using two products with different mechanisms of action,” Bollin explains.

This additive effect can help achieve the reduction typically associated with effective control, particularly on operations where single products no longer meet that threshold. Used alongside approaches like refugia and diagnostic-guided treatment, combination therapy becomes part of a broader strategy aimed at maintaining both short-term efficacy and long-term sustainability.

A More Strategic Future

Taken together, these changes represent a shift away from routine and toward precision parasite management. Instead of relying on fixed schedules, producers are being encouraged to align treatments with parasite biology, use diagnostics to guide decisions and adjust protocols over time.

That shift requires a willingness to rethink long-standing habits. As Jackson points out, progress often starts with being open to change: “We’ve always done it a certain way, but there’s always room to learn and adjust how we’re managing these parasites.”

It also depends on continued collaboration and learning across the industry. Parasite control is not a one-time decision but rather an ongoing process that evolves with new information.

“It’s continual education for both the producer and the veterinarian to understand the life cycle and apply that information to the herd,” Jackson says.

Ultimately, the goal is to move beyond routine and toward more intentional decision-making.

“I think very simply, it’s about not doing it on guesswork like we have been for decades; it’s about using the science and the tools that we have available and being more strategic about how and when we treat,” Bollin says.

Parasites are not going away, but the way they are managed is evolving. Producers who adapt to these new rules will be better positioned to protect both animal performance and the tools they rely on to sustain it.

To hear more from Bollin and Jackson on how deworming strategies are evolving, including where current protocols are falling short, listen to the full conversation on the latest episode of “The Bovine Vet Podcast.”

Stopping Flies in 2026: 4 Steps to Battling These Economic Pests

Wed, 06 May 2026 14:24:43 GMT

With fly season approaching, now is the time to evaluate and refine your fly management plan for 2026.

“Every year, stable and horn flies cause significant economic losses, but a good fly control program can minimize this impact,” says Cassandra Olds, Kansas State University Extension entomologist. “Although often grouped together, these are very different flies that need different control approaches.”

Dr. Ashby Green, Neogen senior technical services veterinarian, says, “If you are seeing flies, ticks, lice or insect damage to your cattle herd, we know there is an economic impact; however, that impact can become far greater than production or weight gain loss alone. Insect pressure affects grazing patterns of cattle; it affects their comfort and it can lead to health issues. Some of those health issues can be definite, such as anaplasmosis.”

The vectors responsible for spreading anaplasmosis include horse flies, stable flies and ticks. This condition has been reported in most states across the U.S., while the disease has been recognized as endemic throughout the South and several Midwestern and Western states.

Jonathan Cammack, Oklahoma State University assistant professor and state extension specialist, says, “With horn flies, we’re looking at mastitis risk, so that’s going to impact both dairy cattle and also our cow-calf operations. A lot of times, horn flies will feed on the udders of the animals, and they transfer the Staphylococcus aureus bacteria because they land on the manure, then they go back to the animal to feed and bring those bacteria with them.”

Several other conditions are propagated by flies, including pinkeye, which can be spread by face flies and causes inflammation and ulceration of the eyes. Pinkeye-affected calves are, on average, 35 lb. to 40 lb. lighter at weaning compared to healthy calves, according to a University of Kentucky report.

Cammack predicts flies are costing the U.S. cattle industry $6 billion annually in losses.

“That encompasses everything from actual loss in production due to decreased weight gain or decreased milk production, veterinary needs associated with treatment of cattle with exposure to pathogens from some of these insects, and then also the control measures associated with managing those individual fly species,” he explains.

David Boxler, Nebraska Extension livestock entomologist, says if previous control efforts underperformed, consider adjusting your approach.
“The best control method will depend on several factors including efficacy, cost, convenience and your current herd management practices,” he summarizes.

He also reminds producers that horn flies can migrate from neighboring untreated herds, masking the effectiveness of your efforts and increasing fly pressure. For this reason, Boxler recommends a comprehensive, integrated fly control.

Olds shares these tips for stopping flies, or at least reducing their impact:

Step 1: Know What You Have

“The first step in developing a good fly control program is knowing who you have,” Olds explains.

(Kansas State University)

Horn flies feed 20 to 30 times a day and stay associated with their chosen animal 24/7, with females only leaving briefly to lay eggs. Stable flies in contrast only feed once or twice a day, remaining on the host for a short period of time (3 to 5 minutes).

When not feeding, flies are resting in shaded areas such as building sides and vegetation. This short feeding time means producers often underestimate their stable fly burdens. While both flies affect pastured cattle, horn flies are not a problem in confined settings such as dairies and feedlots. This is because horn flies need fresh, undisturbed manure as a breeding site while stable flies can develop in any decaying plant matter such as hay bales, feed bunk spill over and decaying grass.

“Their populations can build rapidly and often exceed the economic injury level defined as 200 flies per animal,” Boxler adds about horn flies. “Once fly numbers surpass this threshold, cattle experience reduced weight gain and milk production due to fly-induced stress and altered grazing behavior.”

Step 2: Reduce Populations

Olds explains with either fly species, using non-insecticidal control methods is essential for slowing insecticide resistance. For horn flies, pasture burning in spring kills any flies overwintering, which can significantly reduce fly populations emerging as weather warms. A healthy dung beetle population will also significantly reduce your fly numbers for free.

“Dung beetles are very susceptible to macrocyclic lactones so avoid using injectable and pour-on avermectins (abamectin, eprinomectin, ivermectin etc.),” Olds says.
Because horn flies die within hours of being removed from cattle, non-chemical walk-through traps can be effective if animals pass through it regularly.

Step 3: Eliminate Breeding Grounds

Round hay bales result in significant wastage, which when mixed into the manure-contaminated mud around bales provides a prime breeding site for stable flies.
Olds explains each round bale can produce 200,000 stable flies.

“Reducing hay waste and spreading/drying areas around finished bales is key to reducing stable fly numbers,” she says. “In feedlots, minimizing feed spillage and waste is critical to remove breeding sites for stable and house flies.”

Parasitoid wasps are available from multiple sellers and should be released around fly breeding sites. These are very effective if released before fly populations emerge and released repeatedly through the fly season.

Be careful using insecticides if using parasitoid wasps as they are very small and sensitive to these chemicals. Keeping vegetation surrounding pen areas short and exposed will remove sheltered resting areas, making life more difficult for the flies.

Step 4: Consider Chemical Control Options

Olds stresses chemical control options should be used as a supplement not the basis of a fly control program.

(Kansas State University)

“For horn flies, insecticidal ear tags are an effective method of control if correct rotation is used,” she adds. “Rotate the chemical class of your tag annually, in year one using pyrethroid-based products, year two use organophosphate-based products and year three use macrocyclic lactone tags. Repeating this three-year cycle will reduce the selection pressure on the fly populations, slowing down the spread of resistance.”

Olds also shares these tips for effective tagging: “Tag both ears and place the tag directly into the ear. For the tag to be effective, it must come into direct contact with the animal’s skin, which is greatly reduced when daisy chained.”

Little of the tag touches the body when attached to another tag.

(Cassandra Olds, Kansas State University)

She also instructs producers not to tag young calves and adds mature bulls with thick necks might not benefit from tagging unless the tag can touch the skin.

“Although the box may label products as effective for four to five months, field trials have shown that tags only remain effective for 90 to 100 days,” Olds says. “If possible, wait until fly populations are noticeable before tagging animals to get control over peak fly activity period. After 90 days, remove the tag to reduce the risk of insecticide resistance developing.”

(Neogen)

To increase coverage, pour-ons of the same chemical class as the ear tag can be used to increase coverage.

“Be aware that a macrocyclic lactone pour-on will impact dung beetle populations,” Olds says. “Make sure animals are dosed accurately according to weight and ensure head to tail coverage. Due to their low contact time with the host and preference for the legs, topical insecticidal treatments are generally not useful against stable flies.”

Spraying the legs can provide some relief, although it should be used sparingly as most sprays are pyrethroid-based, not allowing for effective annual rotation. Baits and premise sprays can be useful in controlling both house and stable flies, look for areas where flies are found resting such as building walls, fence posts and inside sheds and shelters.

Another option is feed through insect growth regulators (IGRs) to control horn fly. Olds says it is important cattle consume the correct amount, which can be difficult under free-choice conditions.

“Under-dosing will result in resistance developing over time, reducing product efficacy,” she says. “Although labeled for stable fly control also, when manure containing the IGR is diluted in the mud and hay, it is no longer effective.”

Often marketed as dung beetle safe, Olds says evaluations of these claims in most species have not been carried out, and their true impact remains unknown.

“Insecticide resistance to IGRs can and does happen; to slow this, rotate annually between Methoprene-based (Group 7A) and diflubenzuron-based products (Group 15),” she adds.

The Veterinary Entomology website , veterinaryentomology.org/vetpestx, provides a searchable database that can help producers select the right products. Producers can select from type of animal, insect and application method.

“For on-animal use, select the best product to allow an annual rotation between pyrethroid (Group 3A), organophosphate (Group 1B) and macrocyclic lactone (Group 6) groups,” Olds says.

Green also recommends using a multi-pronged approach to insect control. He says fly tags, IGR products, pour-ons, back rubbers and dust bags can help diminish the population.

“Both back rubbers and dust bags can be highly effective if managed correctly,” Green advises. “Keep in mind, when these are put out to withstand the elements, including moisture and rain, it’s key to keep the dust fresh or the oil recharged in your back rubbers. Otherwise, they will diminish in their ability to control flies quickly.”

Cammack stresses the importance of accurate dosing by the individual animal’s weight and following label guidelines.

To best control flies and insects on cattle operations, “the easy and effective way is the best way,” Green summarizes. “It’s up to you and with the help of your veterinarian to help create that combination.”

Stop the Guesswork: Build a Targeted Parasite Plan

Wed, 01 Apr 2026 15:20:18 GMT

As grass greens up and cattle head back to pasture, many producers are “throwing darts in an open field” when it comes to parasite control, says Tennessee Hereford breeder Ryan Proffitt.

The real-world frustration of deworming programs is knowing if they are working, Proffitt says.

Norbrook Technical Services Veterinarian Megan Bollin explains fecal egg count testing, targeted treatment, concurrent deworming, maintaining refugia and smarter pasture management can turn parasite control guesswork into a targeted plan that protects herd health, preserves dewormer efficacy and ultimately adds pounds to the calf crop.

Both Bollin and Proffitt agree a pragmatic roadmap for modern parasite control is anchored in diagnostics, targeted treatment and strong relationships with veterinarians.

Bollin shares five practical strategies to get the most out of today’s dewormers and preserve them for tomorrow:

1. Sit Down with Your Vet.

She encourages producers to map out a herd‑specific internal and external parasite plan with diagnostics built in.

“Your local vet should be your key partner in designing a program that fits your parasites, climate and management style,” Bollin says.

2. Use the Right Product at the Right Time.

Use the correct class, correct dose and consider concurrent deworming when resistance is a known issue. Your local veterinarian can guide you on proper treatment timing to avoid wasting money.

3. Manage Pastures with Parasites in Mind.

Bollin says pasture management is as important as treatment. Pasture type, quality, topography and drainage should all be considered in your plan, knowing we can’t always do much to change them.

“Only about 10% of the parasite life cycle is in the animal; 90% is on pasture,” she says.

Larvae generally stay below 4” on the grass blade. She says it is important to avoid overgrazing pastures below this height and manage stocking density accordingly.

“When you get a big rain after a drought, the larvae that had been waiting in the manure pats can quickly become infective and significantly increase the risk of infection, especially in young calves,” she says.

4. Prioritize High-Risk Animals.

Calves, stockers, bulls and replacements should be prioritized with the strictest parasite control and monitoring programs.

“Calves, replacement heifers and bulls are typically heavier shedders and more susceptible to the effects of parasites than mature cows,” Bollin explains.

Proffitt notes that many producers historically concentrate on keeping mature cows dewormed while underestimating calves’ role as carriers.

“We don’t need to, and shouldn’t be, treating every animal like we always have,” Bollin adds. “That has gotten us in a pickle with resistance.”

5. Measure and Adjust Treatment.

Bollin says it is important to know where you started. Get a baseline fecal egg count, understand your resistance patterns and monitor the efficacy of your treatment program. So many variables change from year to year: climate, weather conditions, new animals and other stressors. It’s critical to routinely evaluate your deworming program and avoid blindly doing the same thing year after year.

(Proffitt Family)

Diagnostics Are Essential, Not Optional

Fecal egg count reduction tests (FECRTs) are the most practical method we have to determine if dewormers are still working and at what level.

Bollin explains the process includes:

Collecting rectal fecal samples and recording identification.
Treating animals with product or products of choice.
Resampling the same animals by taking rectal fecal samples, 10 to 17 days later, depending on the drug or drugs used.

The lab will count how many eggs per gram are in that fecal sample. There will be a pretreatment and a posttreatment sample. Bollin says the goal should be greater than 95% reduction.

Proffitt argues FECRTs are worth the hassle.

“If we don’t have a game plan on what we’re doing and we’re just rushing,” he says. “What did we win at the end of the day if we don’t know what we’re doing?”

Proffitt says testing tells him which cows he can skip treating, which saves him money.

Bollin explains in many cases mature cows 3 years and older, shedding low levels of eggs, on a good plane of nutrition, with no other stressors or health concerns (including liver flukes), should not need to be dewormed.

“This supports ‘refugia’ — intentionally leaving low-risk animals untreated to slow resistance,” she explains. “Because they’re mature, they’ve got a competent immune system that can actually fight off these parasites by themselves without a dewormer.”

To reduce costs further, Bollin says producers can pool fecal samples from multiple cows into a single submission.

(Deb Gustafson)

Beating Parasite Resistance Starts at the Chute

Bollin says dewormer resistance, long documented in sheep and goats, is being seen more frequently in U.S. cattle herds.

She says overuse, underdosing and treating every animal regardless of need are major drivers in resistance.

“All of these deworming products, when they were originally approved, had very high levels of efficacy. We’re talking 99% and above,” Bollin explains. “As we’ve continually used these products, efficacy has been challenged because resistance has increased.”

If you’re using products that are no longer effective in your herd, you’re spending money on drugs that don’t work, and you’re not getting the production benefits. One way to restore efficacy when resistance is present is to use concurrent deworming.

Why Concurrent Deworming Matters

Bollin says concurrent deworming is using two dewormers from different classes at the same time. She stresses producers need to work with a veterinarian to avoid unknowingly pairing two products from the same class, which doesn’t provide the intended benefit.

She explains the benefits of concurrent deworming are:

· Higher overall efficacy when two partially effective products are combined. “Say you’ve got two products, for example, each with 70% efficacy. By using them together, you can raise your overall efficacy to levels exceeding 90%,” she says.

· Broader spectrum of parasite coverage.

· Models would suggest a slowing of resistance.

· Only sustainable long-term when used in conjunction with a refugia program. This means we don’t treat every animal. We want to keep a few “good” worms around that are still susceptible to the drug.

Bollin gives the example of pairing a benzimidazole, or a “white dewormer,” such as fenbendazole, albendazole or oxfendazole, with a macrocyclic lactone such as ivermectin, moxidectin or eprinomectin.

She emphasizes the industry unfortunately doesn’t have a lot of studies looking at this, but a study published in 2025 highlighted the benefits of concurrent treatment with fenbendazole in situations where resistance to macrocyclic lactones is likely.

Dung Beetles Are Valuable Allies

Dung beetles break up manure pats, exposing eggs and larvae to sunshine and dry conditions. Some dewormers are more compatible with dung beetle health.

“Two of the dewormers that are not harmful are moxidectin and fenbendazole,” Bollin says. “Those are two molecules that are generally safe for dung beetles, and those could be a good option to pair together.”

Facility where researchers collect blood samples and weigh cattle before and after they are transported. Steers have painted numbers on their backs so their activity can be followed on camera.

(Stephanie Hansen)

Application Technique and Dosing Accuracy Matter

Bollin says accurate body weights, not visual estimates, are critical, explaining underdosing is a key driver of resistance.

“One of the biggest contributors to resistance is that we are just not giving them enough active ingredient,” she says. “If you don’t have scales, it is best to treat to the heaviest body weight in the group, so that you make sure that they’re all getting enough.”

She also stresses the importance of storing deworming products correctly.

“Leaving them by the chute in temperature swings can reduce efficacy,” she says.

Proffitt also reminds producers to read labels and understand rain windows with pour-ons and to avoid mud or manure on hides. Bollin notes that injectables can provide more certainty that the animal is getting the full dose, whereas oral drenches can be spit out and pour-ons can run off or be groomed off by penmates.

Both Bollin and Proffitt frame parasite control not as one more chore on an overloaded to-do list but rather as a strategic, data-driven opportunity to protect animal health, slow resistance and convert good management into pounds sold.

Your Next Read:

Determine Parasite Load and Follow With Treatment

Losing a Dollar a Day? The True Cost of Horn Flies on Cattle Performance

Thu, 16 Apr 2026 15:29:19 GMT

Little things have a big impact — and in the case of horn flies, it’s a big economic one.

“When you think about fly control and specifically the horn fly, it is by far the No. 1 nuisance that beef cattle on pasture experience,” says Johnathan Wells, beef field representative for Cargill Animal Nutrition.

Horn flies transfer diseases such as anaplasmosis and mastitis, but treatment costs aren’t the only way they impact the bottom line. These tiny pests also chip away at average daily gain.

“You’re looking at average daily gain differences of about 15% — that’s roughly a third of a pound per day,” Wells says. “In this market, that’s over a dollar per day in lost performance.”

Cattle with heavy fly loads use more energy than those with minimal pressure.

“You have an animal that goes from about 76 beats per minute to over 100 beats per minute under a heavy fly load — that’s a 30% increase in heart rate,” Wells explains.

That increase in heart rate leads to higher water intake and greater urine output. As urine output rises, nitrogen retention decreases — and that’s where the loss in average daily gain shows up.

Targeting the Egg: Why Breaking the Life Cycle Beats Killing the Adult

Controlling flies isn’t new, but evolving methods are worth considering — especially as resistance to traditional products becomes more common.

“Most common products are targeting the adult fly after it’s already affecting the animal,” says Wells. “That’s where we’re running into resistance.”

Targeting the egg stage instead of the adult fly offers a different approach. Feed-through products, such as Altosid, work by interrupting the fly’s life cycle.

“Altosid works by breaking the life cycle of the fly — it prevents eggs from developing into adult flies,” Wells explains.

However, feed-through solutions require consistent intake to be effective.

“A lapse of even a couple weeks in a feed-through program can undo months of progress,” Wells says.

That inconsistency can come from variable mineral consumption or supply issues at the feed store — both real-world challenges for producers.

Consistency is Key: Comparing Feed-Through Mineral vs. Boluses

An alternative is the Altosid IGR XRB bolus, which delivers the same active ingredient without relying on daily intake.

“With the extended-release bolus, you apply it one time and get about 195 days of control,” Wells explains.

The bolus helps ensure consistent delivery while reducing the need for repeated applications.

“Once you put it in, you know it’s in the animal — that consistency matters,” he says.

No matter the method, it’s important to keep expectations realistic.

“The goal is reduction — you’re still going to see some flies, but you’re controlling the population,” Wells says.

And controlling that population directly impacts profitability.

Listen to the full conversation on the “Casual Cattle Conversations” podcast .

New Formulations Aim to Improve How Dewormers Work in Cattle

Mon, 09 Mar 2026 16:31:01 GMT

Before an oral dewormer can kill parasites, it has to dissolve. But new research suggests that step may not always happen as efficiently as expected. In laboratory testing, a commercial oxfendazole tablet released only about 10% of its drug content, prompting researchers to explore new formulations designed to improve dissolution and extend drug exposure in cattle.

Bezerra and colleagues at the Dundalk Institute of Technology in Ireland explored whether reformulating the common benzimidazole dewormer oxfendazole could improve both dissolution and the duration of drug exposure in cattle. The findings highlight an important point: how a drug is formulated can influence how well it works.

The Hidden Step in Deworming: Why Dissolution Matters in Cattle

When an oral anthelmintic is given to cattle, the drug must first dissolve in gastrointestinal fluids before it can be absorbed or interact with parasites in the digestive tract. For drugs like oxfendazole, that step can be difficult. Benzimidazole anthelmintics are poorly soluble in water, which can limit how quickly and completely they dissolve.

In dissolution testing designed to simulate acidic abomasal conditions, researchers found a commercial oxfendazole tablet released only about 10% of its drug content.

Laboratory dissolution tests do not perfectly replicate conditions in cattle. But the pharmacologic principle still applies: if a drug does not dissolve, it cannot be absorbed effectively. For parasites that require sustained exposure to a drug, incomplete dissolution may limit treatment effectiveness.

Why Drug Delivery Is Challenging for Oral Dewormers in Cattle

Delivering drugs to ruminants is more complicated than in monogastric animals. After administration, an oral drug passes through several very different digestive environments. The rumen and reticulum operate near neutral pH, while the abomasum is strongly acidic. The drug then moves into the intestines, where pH gradually rises again.

Several factors can influence how much drug ultimately becomes available to affect parasites:

Rumen dilution, which can disperse oral drugs before they dissolve
Shifting pH environments throughout the digestive tract
Gastrointestinal transit time, which determines how long drugs remain available for absorption
Enterohepatic recycling, where drug excreted in bile re-enters the digestive tract

Many gastrointestinal parasites are exposed to anthelmintics through both systemic drug levels and the drug moving through the digestive tract itself. Because of this, the timing and extent of drug release can influence parasite exposure.

Rebuilding the Tablet: New Formulations for Oxfendazole

To address the dissolution problem, researchers developed experimental oxfendazole tablets using two advanced pharmaceutical manufacturing techniques: hot-melt extrusion and microinjection molding.

These techniques embed the drug within polymer matrices, converting it from a crystalline form to an amorphous structure. Amorphous drugs typically dissolve more readily, improving bioavailability.

In laboratory testing, one experimental formulation released nearly 90% of the drug during dissolution testing, an eightfold improvement compared with the commercial tablet.

The formulation used polyethylene oxide as the primary polymer carrier. When exposed to fluid, the polymer swells, allowing water to penetrate the tablet and gradually release the drug.

The result was substantially more active drug becoming available in the simulated gastrointestinal environment.

Extending Drug Exposure in Cattle

Researchers also explored whether tablet design could extend how long the drug is released in the digestive tract. A second formulation incorporated polycaprolactone along with polyethylene oxide, producing a slower-eroding polymer matrix. As fluid enters the tablet, pores gradually form within the polymer structure, allowing the drug to diffuse outward over time.

In dissolution testing, this formulation released drug gradually over about three days, roughly matching the typical 72-hour gastrointestinal transit time in cattle.

For parasite control, a slow-release system could potentially maintain drug exposure longer and improve efficacy against parasites that require sustained exposure.

Safety Considerations

Because cattle are food-producing animals, both the active drug and formulation components must be safe.

The study evaluated the polymer formulations using liver cell cultures. At concentrations consistent with expected exposure, the materials used in the tablets did not demonstrate cytotoxic effects.

Polymers such as polyethylene oxide are widely used in pharmaceutical formulations because they are biologically inert, stable during processing and compatible with controlled-release drug systems.

What It Could Mean for Parasite Control in Cattle

While the results are promising, the research remains at an early stage. Field trials would be needed to determine whether improved dissolution and controlled-release properties translate into better parasite control in cattle.

Still, the findings highlight an often-overlooked factor in deworming success. The effectiveness of an anthelmintic depends not only on the drug itself, but also on how it is delivered in the animal.

Build Smarter Deworming Plans with Diagnostics

Tue, 03 Mar 2026 15:10:56 GMT

Incorporating diagnostics into deworming plans gives cattle producers a clearer handle on parasite pressure and product performance. It helps confirm when treatment is needed, when it isn’t, and when a protocol might need adjusting.

For operations like Leaning Oak Ranch in Okemah, Okla., that clarity has become a key advantage. And it starts with putting real numbers behind decision-making.

Turning Data into Decisions

Diagnostics provide a straightforward view of the parasite burden in your herd. A fecal egg count reduction test (FECRT) is the most reliable method for measuring deworming efficacy.

“We had a group that didn’t look right, and I assumed it was a worm issue,” shares Buck Rich, owner of Leaning Oak Ranch. “But the fecal tests came back clean, and confirmed our Longrange [eprinomectin] was working the way it should. Running diagnostics saved us from reworking the cows unnecessarily.”

The results also highlighted the economic value of testing.

“From an economic standpoint, that would have been wasted money on more dewormer, and wouldn’t have helped our problem,” Rich continues. “Diagnostics are an important tool, and can definitely help get you on the right path more quickly.”

Rich works closely with his herd veterinarian, Tyler Thomas, DVM, owner and operator of Prague Veterinary Clinic in Prague, Okla.

“It’s very easy to check fecals, and it’s a valuable tool,” Thomas says. “The data lets us know where a deworming program sits, and if we need to take action or not.”

How to Implement Diagnostics

Routine FECRTs establish a baseline on product performance, and track resistance over time. Even a few well-placed tests each year can support better decisions. Testing before spring turnout, during grazing or at weaning are all good options.

“Without diagnostics, it’s easy to point the finger at the product,” explains Jody Wade, DVM, Boehringer Ingelheim. “But if you’re not testing, you might be treating the wrong issue or not seeing the whole picture.”

To conduct the test, two manure samples are needed from the same animal: one collected before or at the time of treatment, and another collected after a specified period following treatment. The timing of the second sample depends on the product used, as each medication requires a different interval after treatment to assess its effect.

When running diagnostics, Wade emphasizes the importance of working with trusted laboratories.

“Samples should be collected per rectum, stored properly and processed by reliable labs,” he adds. “Your veterinarian can help ensure everything is handled correctly, so the results are meaningful.”

An egg reduction of 95% or more indicates the dewormer performed well. When results fall short, it may signal that parasites are surviving treatment. In these situations, a herd veterinarian may recommend adjusting the timing, incorporating combination treatment, modifying the grazing rotation, or reevaluating which cattle receive treatment. The goal is always a plan rooted in evidence — not assumption.

Diagnostics In a Sustainable Deworming Plan

A sustainable deworming plan includes diagnostics and three other proven parasite management tools: combination treatment, pasture management and refugia.

“We want our deworming practices to be sustainable, and the four pillars are about helping producers get the most from the tools we already have,” Wade says. “Diagnostics are where it all begins.”

For Thomas, diagnostic results shape how he builds treatment plans for Leaning Oak Ranch and other operations.

“You don’t know where to go until you know where you’re at,” he asserted. “Diagnostics tell us if treatment is even necessary, and whether what we’ve done is working.”

Reviewing deworming protocols with your veterinarian at least once a year is an essential step in maintaining herd health and productivity. Learn more about diagnostics and sustainable deworming at DewormingLegends.com .

Drive Cattle Productivity with Combination Deworming

Mon, 26 Jan 2026 18:36:44 GMT

Parasites are a hidden drain on cattle performance, quietly stealing productivity and profit from herds across the country.

For producers, the cost isn’t just in lost weight gain, but also in overall herd health and efficiency. That’s why veterinarians and ranchers alike are turning to improved parasite control strategies, like combination treatment.

“Combination treatment is the use of two or more dewormers from different classes, each with a different mode of action, to get more effective control,” says Matt Washburn, DVM, Boehringer Ingelheim.

The advantage? Each dewormer targets parasites in a different way. When used in combination, they can help reduce the number of parasites left behind. In fact, fecal egg counts in cattle herds have been shown to drop by nearly 99% when using dewormers from different classes.

Understand Dewormer Classes For Smarter Control

To get the most out of combination treatment, it helps to understand how each class of dewormer works.

Dewormers can be divided into three different classes, based on their chemical structure and mechanism of action: macrocyclic lactones (endectocides), benzimidazoles (white dewormers) and imidazothiazoles. Each class controls a distinct spectrum of parasites, and for a different amount of time (see Figure 1).

Figure 1: Classes of Cattle Dewormers

(Boehringer Ingelheim)

“Some classes of dewormer do a better job controlling certain parasites than others,” Washburn says. “Endectocides provide strong coverage against both internal and external parasites, while white dewormers work well against only internal parasites.”

There are also differences in how long the dewormers will persist in the animal.

“Most of our macrocyclic lactones have a persistence of about 28 to 30 days, with the exception of the extended-release dewormer, with which we can get out to 150 days,” Washburn says. “On the other side of that, you’ve got the benzimidazoles, which are also known as purge dewormers, because they’re going to clean the animal out, and in two days, they’re gone.”

Putting Combination Treatment Into Practice

Near Okemah, Okla., rancher Buck Rich has been using combination treatment for several years under the guidance of his veterinarian, Dr. Tyler Thomas, to protect his nearly 2,000 cow-calf pairs, as part of his deworming protocol at Leaning Oak Ranch.

“We’ll normally use an injectable, and then we’ll do an oral drench,” said Rich. “It seems to work really well for us, and cleans those cattle up a little quicker. That’s our go-to protocol now.”

Depending on the time of the year, Rich may apply a pour-on dewormer to the calves instead of an injectable, as part of his combination treatment protocol for additional coverage.

Rancher Buck Rich applies a pour-on dewormer to his cattle as his son looks on.

(Boehringer Ingelheim)

Strategic timing can also make combination treatment even more effective, especially when cattle are carrying their highest parasite loads.

“Using combination treatment, you get a better clean-out up front, and you’ll see it on the cattle, particularly coming out of winter, when our highest parasite load occurs,” Thomas says. “They’ll shed that winter coat off, they get fat, and they look good.”

Recommending combination treatment to producers for the first time can sometimes be a tough conversation, because of the additional cost of another dewormer.

“Going from a single class to combination therapy, producers are almost always on a macrocyclic lactone, and they’re adding a white dewormer to it,” Thomas notes. “I would just tell them it’s well worth it, it’s very economical, and it doesn’t take much more effort. If anybody tries combination treatment, they can see the results in the cattle.”

Rich is one of the producers Thomas has worked with who has seen benefits from implementing a combination treatment protocol.

“We’ve seen a drastic change,” Rich says. “The cattle look better. Their hair coat is better. I really think combination treatment is worth it for our operation.”

Dr. Tyler Thomas giving an oral drench dewormer.

(Boehringer Ingelheim)

Combining parasite control programs

Healthy cattle that put on weight and stay in condition are reason enough for Rich to continue implementing combination treatment and other deworming practices advised by Thomas.

“We’re getting paid for pounds of beef at the end of the day,” Rich relates. “Using a quality deworming program helps put on more pounds, which is always a benefit in our business.”

For long-term success that helps drive performance and profitability, combination treatment should be part of a broader parasite control plan that includes:

Diagnostic testing: Performing routine diagnostic tests, such as fecal egg count reduction tests (FECRT) and coprocultures, can help assess the effectiveness of a deworming program and identify the parasites that may be surviving treatment.
Refugia: Intentionally not deworming a small percentage of the herd is recognized as an important factor in delaying the onset of parasite resistance.
Management: Producers can increase overall herd immunity through routine vaccinations and enhanced nutrition. Limit overgrazing, maintain appropriate forage height and rotate pastures, if possible.

When evaluating deworming practices, be sure to include a veterinarian in the process, similar to how Rich and Thomas have collaborated to develop a parasite control plan for Leaning Oak Ranch.

To further investigate combination treatment and the other deworming strategies, tune into Out Here with the Legends , where Buck and Dr. Thomas discuss all things sustainable deworming.

When Cattle Don't Roam: Uncovering Tick Refuges with GPS, GIS and Modeling

Mon, 08 Dec 2025 20:00:46 GMT

Cattle fever ticks persist in South Texas not because eradication efforts have failed everywhere, but because, in some places, cattle never go at all. New research from Texas A&M combining GPS collar data, habitat mapping and individual-based simulation models shows areas rarely visited by treated cattle can function as ecological refuges for ticks, allowing populations to survive long enough to reinfest herds.

For more than a century, eradication programs targeting Rhipicephalus microplus have relied on a straightforward premise: treat cattle, interrupt the tick life cycle, and the population collapses. That approach nearly succeeded nationwide by the mid-20^th century, protecting the U.S. cattle industry from bovine babesiosis, a disease transmitted by the tick. However, in South Texas, particularly at the wildlife-livestock interface, ticks continue to persist despite regular treatment programs.

According to a pair of recent studies from Texas A&M AgriLife researchers, the missing piece might not be chemical efficacy or compliance, but behavior. Specifically, where cattle choose not to roam.

What GPS Tracking Reveals About Cattle Behavior

In the first study , cattle were outfitted with GPS collars to record fine-scale movement across the Texas coastal landscape known to harbor cattle fever ticks. Over extended periods, the researchers tracked when and where animals grazed, rested and avoided, generating a high-resolution picture of habitat use across seasons.

The results revealed that cattle did not use the landscape evenly. Instead, grazing and movement was clustered in specific habitat types while large portions of the pasture, particularly dense brush and shrub-dominated areas favorable to tick survival, remained consistently underused. Seasonal heat stress further amplified this pattern, shifting cattle away from certain habitats for prolonged periods.

These underused areas represent more than idle land. From a tick’s perspective, they are zones where pesticide exposure is low or nonexistent. Even when cattle on the ranch are treated, ticks located in places cattle rarely enter might escape control entirely.

By overlaying GPS movement data with geographic information system (GIS) habitat classifications, researchers were able to spatially define where these behavioral gaps occurred, effectively mapping where cattle presence, and therefore tick control pressure, was weakest.

The Role of Cattle Behavior Models for Predicting Tick Persistence

In the second study , researchers moved from observation to prediction. Using the acquired GPS-derived habitat use data, they built a specially explicit, individual based simulation model to explore how tick populations respond to different host and treatment scenarios.

Unlike traditional models that assume uniform host movement, this framework explicitly incorporates cattle behavior, including their avoidance of specific habitat types, alongside tick life history, habitat suitability and the presence of wildlife hosts, such as white-tailed deer and nilgai.

The simulations tested multiple scenarios: cattle-only systems, mixed wildlife-cattle systems, different pesticide treatment strategies and varying habitat use patterns. Across scenarios, a consistent result emerged. When cattle alone were treated, the standard eradication approach, tick populations frequently persisted in landscapes where cattle avoided substantial portions of tick-suitable habitat.

These persistence zones functioned as refugia: small but stable patches where ticks could survive, reproduce and later recolonize treatment areas. Importantly, the model showed eradication success was strongly influenced not just by those species, but by where hosts traveled across the landscape. Assuming homogeneous grazing behavior significantly overestimated the likelihood of tick elimination.

Why Cattle-Only Tick Control Fails: The Impact of Wildlife and Refugia

The presence of wildlife further compounded the problem. In simulated landscapes shared with deer or nilgai, ticks could cycle through hosts that moved freely through refugia, bypassing treating cattle altogether. Even low densities of wildlife were sufficient to sustain tick populations in favorable habitat patches, especially when cattle presence was inconsistent.

The modeling suggests eradication efforts falter not because ticks are ubiquitous, but because they are spatially selective. They exploit ecological and behavioral gaps. These gaps persist unless control strategies account for where cattle do not go.

Crucially, this research showed changes in grazing behavior, such as increasing cattle access to underused habitats, could substantially reduce tick persistence in simulation. Likewise, scenarios that incorporated treatment or management of wildlife hosts dramatically improved eradication outcomes.

A Spatial Approach to Tick Eradication

Together, the two studies argue for a reframing of tick eradication as a spatial and behavioral challenge rather than a purely chemical one. The failure to eliminate cattle fever ticks in Texas might stem less from insufficient treatment and more from incomplete coverage driven by cattle movement patterns.

This insight has immediate implications. Mapping cattle behavior using GPS data allows managers to identify where control pressure is weakest and to target interventions accordingly. This could be through adjusted grazing plans, focused surveillance, habitat modification or strategic wildlife management.

It all underscores the value of location intelligence in veterinary epidemiology. By integrating GPS tracking, GIS habitat data and individual based modeling, researchers can move beyond reactive control toward predictive, landscape-level strategies that anticipate where persistence is most likely. This reframes eradication not as a question of how much treatment is applied but of whether interventions reach the places cattle do not.

Tackling Winter Lice in Cattle

Mon, 01 Dec 2025 21:11:59 GMT

As temperatures drop and cattle begin experiencing the physiological stressors of winter, external parasites, especially lice, move from being a background nuisance to economically meaningful threats. In a recent discussion on “ DocTalk ,” Kansas State Beef Veterinarian Dr. A.J. Tarpoff outlined what practitioners need to know about lice biology, diagnosis, treatment timing and client communication. Winter-specific parasite management is critical to prevent losses that occur when herds remain untreated or undertreated.

Lice: The Dominant Winter Parasite

Lice remain the most impactful external parasite of cattle during winter months. As Tarpoff emphasizes, lice are highly species specific. Cattle lice do not infest humans, horses or other livestock.

“If your cattle have lice, don’t worry about your kids having lice going to school,” Tarpoff explains. “There are very specific cattle lice that affect our animals.”

This simple clarification can be valuable in client conversations, especially when producers worry about cross-species transmission.

Cattle host two functional groups of lice: sucking lice, which pierce the skin and feed on blood, and biting lice, which feed on skin debris and hair. Both groups spend their entire life cycle on the animal, being mostly dormant in the summer.

“Adult lice will actually hide out in different areas around the ears and eyes,” Tarpoff says. “They really don’t like hot weather, so they go into a dormant state. Now, once the cooler weather starts, that’s where they really jump-start their reproductive cycles.”

Once winter sets in, egg laying accelerates. Eggs, or nits, are cemented to hair shafts with a glue-like substance, hatch into nymphs and develop into egg-laying adults in approximately 28 to 30 days. This predictable cycle can be used to inform treatment expectations and retreatment intervals.

Clinical and Economic Consequences

By the time cattle are visibly rubbing against posts and fences, the infestation is well advanced. The clinical hallmarks of a lice infestations are:

Patchy hair loss over the neck, withers and rump
Intense apparent itchiness and restless behavior
Fence post, building and equipment damage from rubbing
Reduced performance, including decreased average daily gain (by up to 0.2 lb. per day), lower milk production and worsening body condition

“You know when you pull into the feedyard and just kind of zone out and don’t focus on anything,” Tarpoff says. “You look across the yard and all of a sudden say, ‘holy moley, everything’s up against the fence rubbing.’ It’s pretty obvious that we need to have a talk about lice.”

Industrywide, lice contribute to an estimated $125 million in annual losses, a figure driven by reduced productivity and infrastructure damage. Practitioners often struggle to quantify the latter, but any producer who has replaced a stretch of barbed wire knows the cost.

Diagnosing Infestation Before It Escalates

Waiting for obvious rubbing means the opportunity for early intervention has already passed. Tarpoff recommends a practical chute-side evaluation.

“We can part the hair on the neck, the withers, the rump and actually see the little lice,” he says. “They’re about the size of a grain of sand. We can see them scurrying around and if there’s roughly 10 lice per square inch, they definitely need to be treated.”

Fall Deworming Isn’t Enough

Many fall processing protocols include a macrocyclic lactone (pour-on or injectable) intended to clean up internal parasites after summer grazing. While these products provide some lice control, they are imperfect winter solutions. Injectable macrocyclic lactones only kill sucking lice, not biting lice. Pour-ons kill both, but residual activity rarely extends into peak winter months.

This leaves a winter window where live populations surge despite fall treatments. This is often mistaken for product failure rather than an issue of timing and louse biology.

Winter Topical Products for Active Outbreaks

For true winter control, contact-based topical insecticides are the most appropriate tools. These products require direct contact with adult lice to be effective. They do not kill eggs, making retreatment crucial. A second application in two to three weeks ensures newly hatched nymphs are eliminated.

“I see people that are have issues in their cows, and they’ll say, ‘Well, I put it on twice already, and it didn’t do anything,’” Tarpoff says. More often than not, these are issues with the treatment application not covering the entirety of the animal. “The majority of these products … don’t absorb into the bloodstream. They work on contact, and they have to come in physical contact with those lice.”

Don’t Overlook Biosecurity

Even a perfectly executed treatment protocol fails if every animal is not treated. A single untreated bull or newly purchased replacement heifer can reinfest the whole herd within weeks. Tarpoll recommends treating new arrivals upon entry and maintaining a short quarantine period until their lice load is confirmed cleared. This biosecurity step prevents chronic reinfestation cycles.

The key messages for veterinarians to reinforce with their clients are:

Winter lice require winter treatments. Fall dewormers are not a full-season solution.
Coverage matters more than chemistry. Application technique determines outcomes.
Plan for retreatment. One round rarely solves the problem.
Treat the whole herd. Biosecurity is essential for long-term control.

Emergency FDA Approval Sought for Tick-Borne Cattle Disease Treatment

Thu, 20 Nov 2025 19:00:05 GMT

The Ranchers Cattleman Action Legal Fund United Stockgrowers of America (R-CALF USA) has submitted a request to USDA’s Center for Veterinary Medicine requesting emergency approval for the medication buparvaquone to treat cattle infected with theileriosis, the disease transmitted by the Asian longhorned tick (ALHT).

The letter , penned by R. M Thornsberry, chairman of the R-CALF USA Animal Health Committee, asks the FDA to take action to combat the disease, which has been spreading in the United States since 2017 when its carrier was introduced. Since then, the ALHT has been identified in 21 states, most recently as far west as Kansas .

“As a food animal veterinarian, I can prescribe appropriate treatment protocols for tick control, but I must watch my client’s cattle die because I have no approved therapeutic protocols to treat a properly diagnosed case of theileriosis,” Thornsberry writes.

Buparvaquone has a history of use for the treatment of theileriosis in other regions including Asia, Africa, Pacific Island nations and the Middle East. R-CALF USA proposes extended withdrawal times to ensure food safety.

Signs of theileriosis infection in cattle include:

Weakness
Fever
Loss of appetite
Difficulty breathing
Reduced milk production
Foamy nasal discharge

Pregnant cows and calves are most susceptible to infection, and once infected, cattle can be lifetime carriers.

As the ALHT continues to expand its range, the approval of this medicine could be very important for nationwide cattle health.

For more information:
Theileria and the Asian Longhorned Tick: What Beef Producers Need to Know

When Is the Best Time for Lice Control Application?

Mon, 03 Nov 2025 16:44:09 GMT

Lice are a common problem that can cause economic losses, reduce weight gain and lead to a general unhealthy appearance.

“When I hear the word ‘lice,’ two pictures always come to mind; one is me as a kid, lined up with my friends on a cold Idaho morning, waiting for the school nurse to tell us we couldn’t share hats anymore,” says Kirk Ramsey, DVM and Neogen professional services veterinarian. “The other is my cows in winter, rubbing themselves raw against the feed wagon while I beg them to move so I can finish chores in the snow.”

Different scenes, same reminder: As long as mammals have existed, so have lice.

“The reality is that when it comes to lice, ‘an ounce of prevention is worth a pound of cure,’” Ramsey says.

Application Timing and Best Practices

Timing lice control is what makes prevention difficult. One of the most common wintertime complaints cattle veterinarians receive is asking why cattle still have lice even though they were treated the last time they were worked.

“Most spring calving herds do all their herd work in the fall. This means cattle are vaccinated, checked for pregnancy, wormed, and often lice prevention is applied in October or November,” Ramsey explains. “The problem with that logic is that, in many parts of the country, very few lice will be present at that time, and it may be a month or two until the weather deteriorates enough for lice to really be a problem. To reduce risk and create control measures, understanding the life cycle of lice and targeting application times are paramount.”

To achieve seasonlong control, Ramsey says you have to break the life cycle. If treatment is completed too early in the fall, it’s possible only adult lice will be eliminated, not the eggs they laid.

“Producers will not have that seasonlong effect because the life cycle was not broken,” Ramsey says. “Where you will really find success is using a product labeled for lice that has an insect growth regulator (IGR) to help break the life cycle of the louse.”

Selecting a formula that includes an IGR, such as diflubenzuron — which disrupts nymph maturity — minimizes handling time and labor costs.

He adds, “It’s key to note here that most products include an adulticide, which treats adults, but the adulticide will not affect nymphs or eggs.”

When selecting an insecticide, be sure to consider its active ingredients and mode of action.

“It is important to also consider that insecticide resistance may be present in ectoparasite populations in various geographic locations, so a chemical control strategy that rotates between classes of insecticides is recommended,” Ramsey says.

Breaking the Life Cycle of Lice

The key to breaking the life cycle is to first understand how lice develop. First, you have eggs — also referred to as nits — which develop into nymphs within 10 to 20 days, which then transform into adults.

Adults live from two to six weeks, with the female laying 30 to 60 eggs in their lifetime. It may not seem like that massive of a number, but it is a decent number when you’re considering that this is just from one female, and you are never just going to have only one in an infestation.

Signs of Lice

Clinical signs of lice in cattle can include intense itching, patchy and flaky skin, hair loss, lethargy, decreased gain and weight loss.

“Cattle can also get to the point of anemia, when they become very ill looking, and their hair coat will look very poor,” Ramsey explains. “One study from the University of Nebraska, as well as other studies, indicates heavy lice populations may reduce weight gain by as much as 0.21 lb. per day.”

Types of Lice

Ramsey explains there are two types of lice: the sucking louse and the chewing louse.

“In its simplest form, chewing lice feed off skin debris and hair, to some extent, which causes itching,” he explains. “Sucking lice feed on blood, causing anemia and pathogen transmission. The sucking louse can be a biological vector for diseases like Anaplasmosis or Theileria.”

Lice can be present on the skin surface at the base of the hair; they also have a predilection for the face, neck, shoulders, back and tailhead of the animal.

To learn more about lice prevention and control, visit your local veterinarian or visit Neogen.com .

Creepy Crawlies and Spooky Encounters from the Field

Fri, 31 Oct 2025 17:39:52 GMT

The veterinary profession is full of creepy crawlies and spooky animal encounters, and Halloween is the perfect time to swap scary stories. On “ Agriculture Today ,” Dr. A.J. Tarpoff, Kansas State Beef Extension veterinarian, shared some of his creepiest stories from the field.

“Have you ever had the feeling that something or someone was watching you?” Tarpoff recalled one necropsy where he could feel eyes on him, but was initially unsure where that feeling was coming from — until he looked up.

“At the top of the fence, eight feet above me, was a giant bald eagle that was just sitting at me staring very intently,” Tarpoff says. It must have thought Tarpoff was interfering with its meal. In an effort to appease the bird and avoid being the target of its large talons, Tarpoff tossed a chunk of liver in its direction as an offering. As he lives to tell the tale, that offering was enough — for now.

If birds of prey aren’t quite spooky enough for you, Tarpoff wants to remind you that the bubonic plague is still alive and well in the U.S.

“Some of these plagues and diseases we thought were long gone, they’re still around,” he says. “There are still fleas transmitting them. There are animals that are succumbing to them.”

Notably, hikers should take caution if they come into contact with dead wildlife on the trail.

Still not creepy enough? Have you ever heard of cattle grubs?

Caused by the heel fly laying eggs in the feet of cattle, these hatched larvae puncture through the hide then burrow upward into the spinal column or esophagus where they sit in wait as they mature.

“Once they become an adult, they go back into the skin, they bore a little breathing hole and become this big larva that’s just a big knot,” Tarpoff says. “It looks like a huge zit or little abscess that’s right underneath the skin. They sit there and wiggle around. You can see them moving under the skin. It’s disgusting.”

With it being deer season, finding nasal bots within the head of a deer you’re dressing is not uncommon. These bots can also infect sheep, goats and occasionally cattle. Just as the name says, these are grubs that live in the nasal cavity of an animal.

“Don’t be surprised as you’re doing your cleaning and dressing of that carcass that you remove the head or tongue area, and all of a sudden you start seeing some stuff move around,” Tarpoff says. “These little bots start pouring out of the nasal cavity after that animal dies. It freaks people out.”

Halloween is also the season for pranks.

As winter approaches, cases of lice are on the rise, and Tarpoff likes to have a little fun with the crews he works with.

“Whenever I diagnose lice, I’ll go and just start itching,” he says. “I’ll go bare handed and start itching my head until I get everybody in the group itching because they think they’re infested with lice now too. And then I remind them that lice are species specific, so you have nothing to worry about.”

After the parasites, predators and plagues, Tarpoff left veterinarians with one fitting takeaway: “There’s creepy crawlies everywhere. There’s dangerous stuff out there, but it’s good to be aware. Good basic preventative care working with your veterinarian can go a long way in solving a lot of these issues.”

As you head out for your Halloween calls, or your next necropsy, keep your eyes peeled and your gloves handy. You never know who or what might be watching you.

A Deworming Plan that Delivers

Wed, 10 Sep 2025 12:59:57 GMT

For Oklahoma producer Buck Rich and his veterinarian, Dr. Tyler Thomas, parasite control isn’t about doing more. It’s about doing it better.

Together, they’ve fine-tuned a simple, practical approach to parasite control that helps Rich’s herd stay healthy and productive all year long. Their success comes down to four practices that any producer can adopt: diagnostics, combination treatment, refugia and management.

Oklahoma producer Buck Rich (left) and veterinarian Dr. Tyler Thomas, owner of Prague Veterinary Clinic.

(Boehringer Ingelheim Animal Health USA Inc.)

Diagnostics: Start With the Facts

When Rich notices cattle underperforming, his first move isn’t to reach for more product — it’s to collect a fecal sample.

“You don’t know where to go until you know where you’re at,” explains Thomas, a mixed animal practitioner and owner of Prague Veterinary Clinic in Prague, Okla. “Diagnostics tell us if treatment is even necessary, and whether what we’ve done is working.”

Rich’s operation, Leaning Oak Ranch in Okemah, Okla., includes 2,000 pairs. Like many cow-calf operations, it’s heavily forage-based and parasite control plays a key role in performance.

“We had a group of cows that didn’t look right, and I assumed it was a worm issue,” Rich says. “But fecals came back clean. Diagnostics saved us from reworking the cows unnecessarily.”

That kind of clarity is why conducting fecal egg counts, before and after deworming, is a regular part of their plan.

“Without diagnostics, it’s easy to point the finger at the product,” adds Dr. Jody Wade, DVM, Boehringer Ingelheim. “But if you’re not testing, you might be treating the wrong issue or not seeing the whole picture.”

Combination Treatment: Target Parasites in Different Ways

Combination treatment is the practice of deworming cattle by using two or more dewormers from different drug classes. Dewormers can be divided into three different classes, based on their chemical structure and mechanism of action: macrocyclic lactones (endectocides), benzimidazoles (white dewormers) and imidazothiazoles. Each class controls a distinct spectrum of parasites, and for a different amount of time (see Figure 1).

For Rich and Thomas, implementing combination treatment was a game changer.

“We used to rotate products,” Rich recalls. “Now we use a white dewormer and a macrocyclic lactone at the same time. The cattle slick off faster and just look better.”

Figure 1: The three classes of dewormers.

(Boehringer Indelheim)

“Most operations already use a macrocyclic lactone,” Thomas explains. “Adding a white dewormer targets parasites differently. You get more coverage and it’s economical.”

Dr. Matt Washburn, DVM, Boehringer Ingelheim, says combination treatment is one of the most effective ways to slow resistance, while improving outcomes.

“Each class kills different parasites in different ways,” he points out. “When you use a combination of products, you clean up more effectively and reduce the risk of survivors.”

Refugia: Treat the Right Animals

It may go against tradition, but Rich and Thomas agree: Sometimes, the best choice is to skip the deworming treatment. This practice, known as refugia, leaves a portion of the herd untreated to maintain a population of susceptible parasites, helping dilute resistance across the herd.

“We’re wired to treat everything,” Rich says. “But when we’ve held back a few, like Dr. Thomas recommends, it’s worked, and we’re not wasting product.”

Wade notes that skipping treatment isn’t about doing less; it’s about doing what’s right.

“The days of treating everything, every time, are behind us,” he emphasizes. “Refugia takes discipline, but it gives us longevity. It protects the products we have.”

Buck Rich (left) and Dr. Tyler Thomas processing cattle.

(Boehringer Ingelheim)

Management: Strong Grazing Supports Stronger Control

Rich is quick to explain that success doesn’t just come from products; it’s also about how grazing is managed.

“We’re not extreme rotators, but we do move cattle regularly,” he says. “We try to leave about half the grass behind each time. It helps the pasture bounce back faster, and keeps parasite pressure lower.”

Thomas adds that forage height matters.

“Most infective larvae live in the bottom two inches of pasture,” he says. “If cattle graze above that, they’re exposed to fewer parasites. And it’s better for regrowth and soil health, too.”

Washburn agrees and adds, “Overgrazing doesn’t just hurt your grass. It increases parasite exposure and slows pasture recovery. Management is a pillar of deworming, just as much as the product in your chute.”

Planning that Pays

For Rich and Thomas, deworming isn’t a stand-alone decision; It’s part of a year-round plan. And that plan flexes with the season, the weather and the cattle in front of them.

“Herd health protocols aren’t static,” Thomas says. “If Buck’s going to keep calves for 10 months, we make a different plan than if they’re leaving in 60 days. It’s about making the product fit the goal, not the other way around.”

Rich’s partnership with Thomas helps him stay ahead of parasite pressure, while reducing unnecessary costs.

“I know I can call Dr. Thomas any time,” Rich stresses. “He understands our operation and helps me make decisions that actually fit what we’re doing. Working with my vet makes all the difference.”

That tailored approach is one reason Leaning Oak Ranch continues to see results year after year.

“It’s about using the tools we have wisely,” Washburn says. “When you put diagnostics, combination treatment, refugia and management together, you’re building something more sustainable — and profitable.”

For Rich, the proof is in the cattle and the next generation.

“This is a family operation. My kids are growing up on this ranch,” he concludes. “I want our cattle to look good now, but I also want this to work 10, 20 years from now. That’s why we do it this way.”

To explore strategies like the ones Rich and Thomas use visit DewormingLegends.com .

Get Better Drenching Results with These Application Tips

Wed, 27 Aug 2025 18:01:02 GMT

Internal parasites can chip away at cattle performance and profitability if left unchecked. For beef producers using benzimidazoles — commonly known as white dewormers — getting the application right is just as important as choosing the right product.

Leonor Sicalo Gianechini, DVM, Ph.D., University of Georgia, and Nathan Meyer, DVM, Ph.D., Boehringer Ingelheim, share their best advice for improving oral drench results chute-side.

Start with proper placement for effective delivery

“When you’re drenching cattle, it’s important to properly restrain each animal,” Meyer says. “Using a chute or a head catch can help make sure you have good control of the animal’s head while you administer the product.”

For a white dewormer to effectively purge internal parasites, the medication needs to reach the right place in the animal — the rumen. This starts with the correct placement of the applicator:

The hooked end of the applicator should be inserted at the commissure of the lips (the corner of the mouth).
Angle the hook toward the back of the mouth in the cheek, so it gets behind the tongue, not on the tongue.

Gianechini stresses getting the product behind the tongue is essential. If the drench isn’t placed far enough behind the tongue, the esophageal groove reflex may send the drug into the abomasum instead of the rumen, which reduces drench performance.

“You want the medicine to reach the rumen, because with white dewormers, that rumen acts as a reservoir,” Gianechini says. “The drug mixes with the particles in the rumen, and then is slowly released into the abomasum. The abomasum has an acidic pH, causing the drug to be dissolved and properly absorbed in the small intestine. This is why the correct technique of getting white dewormers behind the tongue is an absolute must.”

Get the product where it works best

White dewormers are usually in and out of an animal’s system within a couple of days. Meyer says oral drenches work well, because the gastrointestinal tract is the largest absorptive surface of the body. That large surface area means the oral drench has more contact with parasites, which improves its effectiveness.

“If you want good drug efficacy, the main thing is that the worm has to be in contact with the drug for a certain period of time, so the drug can pass through the cuticle (in nematodes) or tegument (in cestodes) and enter the parasites,” explains Gianechini. “The longer the contact between the active ingredient and the parasite, the better.”

Prevent waste with patient application

Drenching is a task in which slow and steady gets the best results. Impatience, and thus improper placement, can result in regurgitation and wasted product.

“Sometimes, based on how cattle are moving around, patience is our biggest ally,” Meyer points out. “You have to take your time and make sure the hook is inserted fully without forcing it. You can damage the mouth or esophagus if you force it. It may take some maneuvering to get the V of the hook clear to the commissures of the lips. Then depress the applicator all the way, slowly and steadily.”

Meyer recommends using a low-dose, highly concentrated product, like Synanthic® (oxfendazole oral suspension), to do the job cost-effectively . “With some of the large-dose products, you’ll see more waste during application because those animals can’t hold that much product in their mouth,” he explains. “It won’t always go down easy, and they’ll tend to spit more of it up.”

Avoid underdosing with accurate animal weights

Aside from proper application, drenching efficacy also hinges on delivering the right dose. “Underdosing is a high-risk practice when it comes to the development of drug resistance,” Gianechini notes.

Meyer explains that underdosing parasites causes them to create a response to the drug instead of being killed. Because a parasite’s life cycle is short, that response gets carried into the genetic material of the next generation, which can lead to resistance.

To avoid underdosing, it’s important to get accurate weights of the cattle receiving the drench. Using a scale to weigh each animal in the chute is ideal, but when that’s not an option, both doctors suggest taking the weight of the heaviest animal in the group and dosing the group according to that animal.

“When you don’t have the exact weight, it’s always better to give them a slightly higher dose versus underdosing,” Gianechini concludes. “You’ll have a big issue if parasites survive.”

Handle and store drenches with care

Correct application and dosing are only part of the equation. How the product is handled and stored also impacts performance.

“White dewormers can settle in the bottle, so make sure to mix the bottle while you work,” Meyer emphasizes. “You want to make sure that you’re giving the active ingredient at the correct concentration. I always try to shake the bottle every 20 to 30 head when I’m processing cattle to make sure that it’s a uniform dose given to the animals.”

It’s important to also double-check that the applicator’s dose is set appropriately throughout working the cattle, because the dial can easily get bumped. Any extra air in the barrel will reduce the correct dose, which is common when switching to a new bottle. Take a quick look at the barrel to ensure air is out of the system and the product takes up the entire space.

Lastly, always read the product label to get instructions on proper storage. Most white dewormers should be kept between 32 and 77 degrees Fahrenheit to maintain product efficacy. If working cattle during a hot day, Meyer suggests using a smaller bottle size or storing it in a cooler.

Before choosing an oral drench, consult with your veterinarian. They’ll be able to help decide how drenches fit into a well-rounded and sustainable deworming program, and verify whether an oral drench is best for your operation’s parasite load.

Emergency Use of Animal Drugs Approved to Combat New World Screwworm

Tue, 19 Aug 2025 16:08:11 GMT

The U.S. Department of Health and Human Services (HHS) issued a declaration on Aug. 19 allowing the U.S. Food and Drug Administration (FDA) to issue Emergency Use Authorizations (EUAs) for animal drugs to treat or prevent infestations caused by the New World screwworm (NWS).

This declaration applies only to drugs for animals. NWS infests warm-blooded animals, including livestock, pets, wildlife, and, in rare cases, humans, causing severe tissue damage and sometimes death. The risk to human health in the U.S. remains very low, but the potential future threat to animal populations and the food supply chain requires proactive action.

Although eradicated from North America and Central America decades ago, NWS has progressed north since 2022 and is now approaching the U.S. border with Mexico. This parasite poses an emerging threat to livestock and food security, with potential impacts on both national security and animal health.

“Today we are taking decisive action to safeguard the nation’s food supply from this emerging threat,” says HHS Secretary Robert F. Kennedy, Jr. “This authorization equips FDA to act quickly, limit the spread of New World Screwworm, and protect America’s livestock.”

Currently, there are no FDA-approved drugs for NWS in the U.S. The FDA through an EUA can authorize the flexible, faster use of certain animal drug products that may be approved for other purposes, or available in other countries, but not formally approved for NWS in the U.S. This ensures veterinarians, farmers, and animal health officials have timely access to the tools they need to protect pets, livestock and the nation’s food supply.

“Thank you to my friends and partners Secretary Kennedy and Commissioner Makary who are answering the call and supporting our aggressive plan to push back and ultimately defeat this devastating pest. This emergency use authorization is another tool we can use in the fight against New World Screwworm,” says Secretary of Agriculture Brooke L. Rollins. “Our cattle ranchers and livestock producers are relying on the Trump Administration to defend their livelihoods. Stopping this pest is a national security priority and we are linking arms across President Trump’s cabinet to defend our borders and push back this threat.”

FDA Commissioner Marty Makary, M.D., M.P.H., adds, “Our priority is to safeguard both animal health and the nation’s food supply. FDA is acting swiftly and responsibly to help ensure we have the necessary tools to prevent and control New World Screwworm, minimizing risks to agriculture and public health.”

FDA will provide future guidance to veterinarians and stakeholders on the appropriate use of any products authorized for emergency use and update the New World Screwworm: Information for Veterinarians page.

Montana Veterinarian Encourages a Fresh Look at Deworming Protocols

Thu, 26 Jun 2025 14:44:44 GMT

“We’ve always done it this way” is known to be the most dangerous phrase in business, and the cattle business is no exception, says Perrie Neal, DVM, from Hardin, Mont. With more than a decade of experience working with cow-calf producers, she says it never hurts to take a fresh look at your herd’s deworming program to identify potential areas of improvement.

Neal manages her own herd of registered and commercial Angus alongside her husband and father-in-law. When possible, she likes to test out products and practices on their own cattle before she makes recommendations to her customers.

“It’s great to have that firsthand experience,” she says.

Over the last few years, Neal has worked to optimize the timing of her deworming program — and now she tries to deworm calves as early as possible each season for maximum benefit.

“Weaning weights are really important, especially in our registered cows,” she says. “By administering a dewormer early in the season, you can help ensure calves won’t have to carry a heavy parasite load and are more likely to meet their genetic potential.”

Neal also has looked closely at the dewormer route of administration and product efficacy — and encourages her customers to do the same.

“Convenience is a big factor when it comes to deworming programs, so a lot of my customers have historically used pour-ons for that reason,” she explains. “But a lot of times, the injectable dewormers can improve labor efficiencies and help ensure more accurate dosing.”

That’s one of the reasons Neal says she has come to appreciate Valcor^® (doramectin and levamisole injection), a dual-action, single-dose, injectable dewormer.

“We weighed calves as they came in the chute, and my husband would yell out the number as they got on the scale,” she says. “I was able to quickly adjust the dosage depending on the weight of the calf. I love that about the product.”

The Importance of Calf Preconditioning

“Preconditioning calves is another thing that I’ve been highly recommending to producers in the last few years,” Neal says.

Preconditioning programs promote calf growth, enhance immune function and minimize stress as calves move from their ranch of origin to the stocker or backgrounder operation and then to the feedlot.

“Preconditioning can help set calves up for their next production phase, but it also benefits any calves that producers want to retain as replacements,” Neal explains. “We used to just precondition the bulls and the replacement heifers, but over the last few years we’ve switched to preconditioning everything, and we’ve seen a lot less sickness across the board.”

Neal encourages producers who are thinking about taking a fresh look at herd health or deworming protocols, to consult their herd veterinarian. These local experts can help you identify products and practices that make sense for your operation.

Your Next Read: 5 Strategies to Help Cattle Cope with Heat

Urgency in Action: We Must Eradicate New World Screwworm

Tue, 03 Jun 2025 13:00:12 GMT

New World screwworm (NWS) continues to threaten the U.S. cattle industry. The potential impact is devastating — the larvae can kill an animal in just four to seven days if not quickly detected and treated.

Colin Woodall, National Cattlemen’s Beef Association CEO, discussed the hurdles of controlling the spread of NSW on the latest episode of the “Unscripted” podcast .

“We have to eradicate it from here,” Woodall stresses. “We need to eradicate it from Mexico. We need to eradicate it from Central America. We need to push this thing all the way back down to South America.”

The NSW fly and its larvae are flesh-eating parasites that pose a significant threat to warm-blooded animals.

“This is not just a cattle issue,” Woodall says. “This could be dogs. This can be cats. It can get into people. So, anything that is warm blooded could be a host for this flesh-eating parasite.”

Woodall says NSW is approximately 700 miles from the U.S. border, having breached the isthmus of Mexico in the states of Oaxaca and Veracruz, adding that Texas is expected to be the first point of entry if the fly continues to move north.

“We’re going to look at every eradication option possible, because we have to get rid of this thing,” he says. “This is not something that can become endemic to United States. We have to eradicate it from here.”

Woodall says the situation has been complicated by cooperation challenges with Mexico. Earlier attempts to transport sterile flies were hindered by bureaucratic obstacles, with planes unable to land and flies dying before deployment. This led Agriculture Secretary Brooke Rollins to close the border, sending a clear signal to the Mexican government about the need for more serious action.

He explains cooperation has reportedly improved, with USDA teams planning to visit Mexico to assess the current situation. The primary strategy for control involves releasing sterile flies into the wild to disrupt breeding and push the population back southward.

Woodall says NCBA is actively working on several fronts to address the threat:

Pushing for the establishment of a domestic sterile fly production facility.
Exploring genetic engineering technologies for fly control.
Investigating treatment options (such as ivermectin) and helping producers understand how to detect and treat potential infections quickly. Woodall says treatment is possible, explaining ivermectin has proven effective in killing larvae and treating wounds. However, early detection is crucial due to the rapid progression of infection.
Conducting education and awareness campaigns to explain the threat without causing panic. He says misinformation has been a significant challenge. A recent false report about NSW in Missouri caused panic and temporarily impacted cattle prices. He adds that while the threat is serious, it’s not a cause for panic.

“While everybody needs to be aware, they don’t need to panic, and that’s the thing we want everybody to understand,” Woodall summarizes.

NCBA is taking an active role in addressing the threat of NSW through education, technological exploration, government collaboration and a clear commitment to preventing its spread.

Your Next Read: Secretary Rollins Announces $21 Million Investment to Renovate Fruit Fly Production Facility

Five Pre-Pasture Turnout Tips

Wed, 28 May 2025 15:15:33 GMT

Pasture turnout is an important time in a cow herd management calendar. It is critical to make sure both the forage and cattle are ready before opening the pasture gate.

Considering your cow herd, what should you consider before turnout? AJ Tarpoff, DVM and Kansas State University Extension veterinarian, shares his top five tips producers should consider before sending cattle to pasture this summer.

Perform Spring Herd Health Program. Tarpoff reminds producers the importance of doing bull breeding soundness exams before putting the bull to work. He also encourages producers to do pre-breeding vaccinations, consider synchronization options and plan for common pasture ailments such as foot rot and pinkeye .
Make a Plan for Internal/External Parasites. Now is the time to decide how you are going to tackle flies, ticks and internal nematodes. Aaron Berger, University of Nebraska beef systems Extension educator, reminds producers there are several options available to help control flies and to consider the option that works best for your management plan.
Establish Summer Mineral Program . Tarpoff encourages producers to prepare mineral feeders and calculate needs and delivery intervals.
Assess Forage and Fences. Tarpoff says it is important to walk fence lines and scout pastures to determine forage and water availability. “Be sure to check forage availability and make any stocking rate adjustments, if necessary,” he says.
Check Cattle Identification. Be sure cattle are identified before turnout. This can include brands if required in your area or tags. Along with identification, Tarpoff shares these tips for protecting cattle from theft: lock gates and don’t leave cattle penned up overnight in an easily accessible location. He also encourages producers to communicate with neighbors who share a fence line when turning out about what types of cattle are going and how the cattle are identified.

Ron Lemenager, Purdue beef specialist, reminds producers to watch for two potential health issues that can occur at grass turnout: grass tetany and bloat .

Minimize Grass Tetany Risk

Early season lush pasture grasses are high in water content, potassium and soluble nitrogen, but low in magnesium and energy content. It should be noted that pastures containing legumes provide a grazing diet that is somewhat higher in magnesium.

“ Grass tetany can be a problem, especially in older lactating cows that are less efficient in mobilizing magnesium from body stores,” Lemenager explains. “Feeding a high magnesium mineral for several weeks prior to turnout is a standard recommendation to minimize the incidence of grass tetany.”

He reminds producers magnesium, usually in the form of magnesium oxide, is not palatable. Therefore, it is important that mineral intake be monitored.

Watch for Bloat

Lemenager says legumes are beneficial to diet quality — providing nitrogen for companion grasses and increased forage production — but lush legumes can cause bloat . As legumes advance in maturity, the risk for bloat does decrease.

He shares these recommendations to minimize the incidence of bloat:

Prior to turnout, survey the pasture. Look for large areas in the pasture where legumes are the predominant forage. These areas seen to attract cattle and can exacerbate the bloat problem.
Make sure cows are full of a dry forage, such as hay, at turnout to reduce the risk of immediately consuming a large meal of lush legumes.
Don’t turnout until the forages are dry. Wet forages (dew or rain) reduce the amount of saliva production as cattle consume and swallow forages. Saliva is important not only as a rumen buffer to control rumen pH, but also as a surfactant that can reduce the surface tension of stable gas bubbles (frothy mass) formed during rumen fermentation.
Poloxalene containing supplements fed prior to turnout and during the early grazing season act as a surfactant to weaken the surface tension of the stable foam and reduce the risk of bloat.

Through following these strategies with accurate planning and preparation, pasture turnout can be stress free for both the producer and the cow herd.

Your Next Read: Pasture Turnout Tips: Optimum Forage Strategies

More Than Annoyance: Flies Can Impact Health and Profits

Tue, 06 May 2025 15:16:34 GMT

With fly season approaching, now is the time to evaluate and refine your fly management plan for 2025.

“If your 2024 control efforts underperformed, consider adjusting your approach,” says David Boxler, Nebraska Extension livestock entomologist. “The best control method will depend on several factors including efficacy, cost, convenience and your current herd management practices.”

He also reminds producers that horn flies can migrate from neighboring untreated herds, masking the effectiveness of your efforts and increasing fly pressure. For this reason, Boxer recommends a comprehensive, integrated fly control.

The horn fly is one of the most damaging pests of pasture and rangeland cattle across the U.S., Boxler says in a recent “ UNL Beef Watch .”

“Adult horn flies are blood-feeding insects that take an average of 30 blood meals per day,” he says. “Their populations can build rapidly and often exceed the Economic Injury Level defined as 200 flies per animal. Once fly numbers surpass this threshold, cattle experience reduced weight gain and milk production due to fly-induced stress and altered grazing behavior.”

Observing your cattle during summer months is key to detecting fly pressure. Boxler asks, “Are they constantly tossing their heads, swishing their tails or twitching their skin?”

These signs of fly irritation indicate a more effective control strategy might be needed.

“If you are seeing flies, ticks, lice or insect damage to your cattle herd, we know there is an economic impact; however, that impact can become far greater than production or weight gain loss alone,” says Ashby Green, DVM, Neogen senior technical services veterinarian. “Insect pressure affects grazing patterns of cattle, it affects their comfort and it can lead to health issues. Some of those health issues can be definite, such as anaplasmosis.”

The vectors responsible for spreading anaplasmosis include horse flies, stable flies and ticks. This condition has been reported in most states across the U.S., while the disease has been recognized as endemic throughout the South and several Midwestern and Western states.

“With horn flies, we’re looking at mastitis risk, so that’s going to impact both dairy cattle and also our cow-calf operations,” says Jonathan Cammack, Oklahoma State University assistant professor and state extension specialist. “A lot of times, horn flies will feed on the udders of the animals, and they transfer the Staphylococcus aureus bacteria because they land on the manure, then they go back to the animal to feed and bring those bacteria with them.”

Several other conditions are propagated by flies or ticks, including pinkeye, which can be spread by face flies and causes inflammation and ulceration of the eyes. Pinkeye-affected calves are, on average, 35 lb. to 40 lb. lighter at weaning compared to healthy calves, according to a University of Kentucky report.

Cammack says that due to flies, “We’re looking at probably $6 billion in losses annually to U.S. cattle production, and that encompasses everything from actual loss in production due to decreased weight gain or decreased milk production, veterinary needs associated with treatment of cattle with exposure to pathogens from some of these insects, and then also the control measures associated with managing those individual fly species.”

Ticks present economic risks as well. Cammack says that during a 100-day growing period producers can see a decrease in total weight gain in calves by about 20 lb. For stockers, over that same 100-day period during the summer months, they can experience a decrease in weight gain by about 60 lb.

“With what current prices are, 60 lb. could translate to a significant amount of money returned when we’re talking about the few dollars that it might cost for some tick control,” he says.

(Neogen)

Controlling flies and insects: Tips to implement
Now is the time to take steps to control flies and ticks, as populations emerge with the warmer weather.

In “ Stopping Flies in 2025: Tips to Battle These Economic Pests ,” Cassandra Olds, Kansas State University Extension entomologist, shares four steps to controlling flies

Know what flies you’re dealing with.
Reduce populations.
Eliminate breeding grounds.
Consider chemical control options.

Similar to Olds, Green recommends using a multi-pronged approach to insect control. Fly tags, feed-through insect growth regulator (IGR) products, pour-ons, back rubbers and dust bags can help diminish the population. A pour-on with an IGR destroys the larval development in flies and greatly reduces the fly population. For ultimate control using a pour-on, look to a unique combination of actives within one solution that includes an IGR, an adulticide, and a synergist that supplies relief to cattle from infestations and provides producers with a reliable solution that helps minimize handling, time and labor costs.

“Both back rubbers and dust bags can be highly effective if managed correctly. Keep in mind, when these are put out to withstand the elements, including moisture and rain, it’s key to keep the dust fresh or the oil recharged in your back rubbers. Otherwise, they will diminish in their ability to control flies quickly,” Green advises.

Cammack stresses the importance of accurate dosing by the individual animal’s weight and following label guidelines.

To best control flies and insects on cattle operations, “the easy and effective way is the best way,” Green summarizes. “It’s up to you and with the help of your veterinarian to help create that combination.”

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Streamline Spring Cattle Processing with These 3 Stress-Reducing Steps

Thu, 01 May 2025 11:23:00 GMT

Reducing stress during livestock handling can increase productivity, maintain or improve meat quality, reduce sickness and enhance animal welfare. Implementing low-stress handling techniques when working with cattle is important to reducing stress.

As producers prepare for spring processing, Beth McIlquham, University of Wisconsin-Madison regional livestock educator, encourages producers to consider these low-stress handling strategies.

“While temperament in cattle is moderately heritable, environment does play a role and even cattle that are less docile will benefit from low-stress handling methods,” Mcllquham says. “A good handler can help reduce fear in an animal, which is the primary driver of negative consequences associated with handling stress.”

Even if the animal is not experiencing any pain, fear can still cause physical responses in the body, such as high cortisol levels. These responses can ultimately lead to increased susceptibility to illness, lower meat quality and overall lower performance.

Mcllquham says one negative handling experiences can affect future handling situations.

Identifying stress through body language
Cattle in a state of fear or under stress can be identified through their body language. Obvious signs of fear in cattle are running, kicking, vocalizing and aggressive behaviors toward handlers. Subtle signs of fear are heavy breathing and showing the whites of their eyes. Stressed cattle can cause serious injury to themselves and humans. Relaxed cattle are quiet and walk or trot calmly. When low-stress handling techniques are used, the risk of injury is lowered.

“Besides increasing performance and lowering sickness and injury rates, consumers have indicated that they care that their food is humanely raised,” McIlquham explains. “Implementing low-stress handling is a great place to start and comes with many other benefits. Although it may sound like a daunting task, utilizing low-stress handling techniques can be done in smaller steps.”

Step 1: Put away the electric prod
“Our first step is to put away the electric prod,” she says. “To decrease use, place electric prods away from where you’re handling cattle but still be accessible in an emergency. This way, instead of instinctively reaching for it, the inconvenience of going to grab it can decrease electric prod use.”

Step 2: Understand cattle’s natural instincts
“We should utilize these instincts to work for us instead of against us,” she says. “The fact that cattle are prey animals drives a lot of their behaviors.”

Cattle are herd animals and like to be in groups. When moving them, keeping cattle in small groups (two to five head) can help keep them calmer and easier to handle. Additionally, cattle want to see you. Humans are naturally predators, and because cattle are prey animals, their instinct is to be able to keep handlers in sight.

Cattle want to go toward lighted areas and will resist going into darker areas. It is easier to see any potential threats in areas that are light. Keep in mind shadows can reduce cattle flow through an area.

Step 3: Study and use cattle’s natural flight zone
Good handlers study and use cattle’s flight zone and point of balance, McIlquham explains.

Two concepts are illustrated in Figure 1.

Figure 1. Flight Zone and Point of Balance

(Beef Quality Assurance Cattle Care & Handling Guides)

Walking into the flight zone makes the animal move away from the handler. Stepping out of the flight zone will take pressure off and remove the animal’s desire to continue to move away. Note that the size of flight zones varies between animals. The point of balance allows handlers to move the animal forward or backward. Stepping into the flight zone in front of the point of balance will make the animal move backward. Stepping into the flight zone behind the point of balance will drive the animal forward.

Keep in mind cattle have a blind spot directly behind them. If you approach the animal in the blind spot, they could get spooked. Walking in a zigzag pattern behind cattle helps let them know you are there.

Extra tip: Taking breaks
Calm cattle are easier to move than stressed cattle. Fearful cattle are more reactive, more easily injured, and more likely to engage in aggressive behaviors. If a handling situation does get intense, take a little break and release pressure on the cattle.

“Even taking a brief break can help both the animal and handler calm down and come back to the situation in a more positive light,” Mcllquham summarizes.

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Mexico Takes Additional Measures to Help Fight New World Screwworm

Thu, 01 May 2025 18:11:39 GMT

USDA has announced that Mexico agreed to additional measures to help fight New World Screwworm (NWS). The U.S. had given Mexico a deadline of April 30 to follow protocols in place or the U.S. would put restrictions on cattle imports.

USDA Secretary Rollins posted on X.com that Mexico has resumed efforts to help fight NWS with the following:

Eliminate restrictions on USDA aircraft
Waive customs duties on eradication equipment
Increase surveillance

(X.com)

Rollins says ports will remain open to livestock imports at this time, however if at any time these terms are not upheld, port closure will be revisited. The secretary had sent a letter to Mexico outlining the expectations for cooperation on the issue.

Protocols had been established in February after the pest was discovered in southern Mexico in November 2024.

“I am happy to share Mexico has continued to partner in emergency efforts to eradicate the New World Screwworm,” Rollins says. “This pest is a devastating threat to both of our economies, and I am pleased to work together with Mexico in good faith to protect the livelihoods of our ranchers and producers who would have been hurt by this pest.”

Rollins reiterated that USDA is working every day to keep pests and disease from harming the agricultural industry.

“I thank our frontline USDA staff and their counterparts in Mexico for their work to ensure the screwworm does not harm our livestock industry,” she adds.

NWS is a deadly parasitic fly that infests warm-blooded animals, causing severe wounds and complications that can lead to death.

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USDA Threatens To Halt Imports If Mexico Doesn't Step Up New World Screwworm Control

Mon, 28 Apr 2025 22:12:35 GMT

President Donald Trump’s administration warned on Saturday it will restrict livestock imports from Mexico if the Mexican government doesn’t intensify its fight against New World Screwworm.

Washington’s threat came in a letter from Agriculture Secretary Brooke Rollins that said Mexico had limited one of the companies hired to conduct aerial spraying to eliminate the pest to flying only six days a week and had imposed “burdensome customs duties” on parts needed to keep its planes in the air.

USDA is only giving Mexico until April 30 to follow protocol to stop the spread of the pest and eliminate current restrictions slowing eradication. If not, the U.S. will halt imports of Mexican cattle, bison and equine.

Buck Wehrbein, president of the National Cattlemen’s Beef Association, says the threat comes as additional cases of screwworm have been detected in far southern Mexico. At the same time, the sterile insect technique used for eradication has stalled.

“There’s a production facility for the sterile flies to stop this nasty little bug in Panama, so we’re in good shape to do it and things have moved forward, but there’s been some snags now with planes not being allowed to land by the Mexican government and some extra fees and customs,” Wehrbein explains.

He met with senior officials at the Embassy of Mexico in Washington, D.C., last week to press for further action.

“It’s simply a bureaucratic thing that I would think all they have to do is the right person sign the right paper that says you can land these planes,” Wehrbein says.

Mexico’s President said Monday they are strengthening efforts to stop the pest.

Reopening the border to Mexican feeder cattle has been a steady process since the pest was detected last November , yet trade has not fully normalized.

"[Trade is] at about half capacity compared with before,” Wehrbein says. “It’s come a long way and the Mexican government has done a really good job on the border and working with our APHIS people.”

In the 1960s, the U.S. spent million of dollars to eradicate New World Screwworm, but the pest is destructive and could cost producers millions of dollars a year if it reaches the U.S.

Cattle and Bison Imports from Mexico to Resume Under New Protocols

Mon, 03 Feb 2025 14:43:58 GMT

On Feb. 1, the United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) announced cattle and bison imports from Mexico will resume utilizing new preventative measures. Imports are scheduled to begin in the next several days.

In November 2024, APHIS halted shipments of Mexican cattle and bison after a positive detection of New World screwworm (NWS) in southern Mexico.

According to the release, APHIS and Mexico agreed to and implemented a comprehensive pre-clearance inspection and treatment protocol to ensure safe movement and mitigate the threat of NWS. APHIS says its top priority is to protect American livestock from foreign pests.

Newly released preventative measures include:

Mexico identified and prepared pre-export inspection pens in San Jeronimo, Chihuahua, and Agua Prieta, Sonora, which APHIS visited, inspected, and approved.
Cattle and bison will be inspected and treated for screwworm by trained and authorized veterinarians prior to entering the pre-export inspection pens, followed by inspection by Mexican officials before proceeding to final APHIS inspection before crossing at the Santa Teresa and Douglas Ports of Entry, respectively.
Cattle and bison approved for importation will also be dipped in a solution to ensure they are otherwise insect- and tick -free.

The United States and Mexico are working closely to approve additional pre-export inspection pens and reopen trade through other ports of entry, the release says.

APHIS will continue working with partners in Mexico and Central America to eradicate NWS from the affected areas and to reestablish the biological barrier in Panama, which has been maintained since 2006.

In the last two years, screwworm has spread north of the barrier throughout Panama and into Costa Rica, Nicaragua, Honduras, Guatemala, El Salvador, Belize and now Mexico.

The APHIS release says the increase is due to multiple factors including new areas of farming in previous barrier regions for fly control and increased cattle movements into the region.

APHIS is releasing sterile flies through aerial and ground release at strategic locations, focusing on Southern Mexico and other areas throughout Central America.

A complete list of regions APHIS recognizes as affected by screwworm as well as more detailed information on trade restrictions can be found on the USDA APHIS Animal Health Status of Regions website .

More Action Needed By Mexico Before Reopening Border for Feeder Cattle Imports, Says Vilsack

Sun, 19 Jan 2025 20:54:32 GMT

A letter sent Friday by outgoing USDA Secretary Tom Vilsack to Mexico’s Secretary of Agriculture Julio Antonio Berdeguê acknowledges the progress made in reopening cattle trade between the two countries following the detection of New World Screwworm (NWS) in Mexico, but says more action is needed to resume trade.

Key developments:

Technical collaboration between U.S. and Mexican teams
Full technical agreement on protocol reached on Dec. 12, 2024
Ongoing work to approve pre-export NWS inspection facilities.

Vilsack emphasizes the importance of expediting the approval process for these facilities to resume safe export as soon as possible, citing the significance of trade for a safe and affordable food supply.

The letter also addresses efforts to combat the spread of New World Screwworm:

Emergency funding has been authorized to increase sterile fly production
Production has increased fivefold in the past year
Enhanced regional response through increased dispersal, surveillance, education, and partnerships
Acknowledgment of Mexico’s partnership in sterile fly releases, movement controls, and surveillance
Shared goal to push the pest south to the Darien Gap

Vilsack requests immediate support from Secretary Berdegué for the establishment of two planned sterile fly dispersal centers in Southern Mexico to strengthen current efforts.

The letter maintains a cordial and cooperative tone throughout, emphasizing:

Shared commitments and goals
Acknowledgment of Mexico’s efforts and partnership
Expressions of gratitude for collaboration
Requests for continued support and expedited action

Industry sources say specific testing will take place Monday, Jan. 20, and that and other tests will go a long way in establishing a trade resumption timeline.

NWS Trade Impacts Started in November
As previously reported, USDA’s Animal and Plant Health Inspection Service (APHIS) suspended imports of live cattle and bison from Mexico on Nov. 22, 2024, following the detection of New World screwworm (NWS) along Mexico’s southern border. This pest can have a significant negative impact on cattle health, and U.S. authorities have been working to develop protocols to screen animals coming into the country.

Several factors are influencing the timeline and pace of reopening:

Facility inspections: Both countries have agreed on protocols, but implementation requires facility inspections and approvals.
Quarantine period: A seven-day quarantine after animal checks
Port readiness: The most important port to get moving again is Santa Teresa, New Mexico.

The temporary suspension of cattle imports from Mexico has had notable effects on the U.S. cattle market:

Reduced supply: About 250,000-300,000 fewer head of cattle are estimated to have been imported due to the suspension.
Price support: The trade disruption has been supporting feeder cattle and calf prices in the U.S.

New World Screwworm is Moving Toward the U.S.

Wed, 08 Jan 2025 20:15:31 GMT

By Kathy Simmons, DVM, Chief Veterinarian, National Cattlemen’s Beef Association

The U.S. cattle industry has not faced the threat of New World screwworm (NWS) for over 60 years. Currently, the NWS fly, about the size of a common housefly, has migrated across Central America from Panama and entered Mexico.

Live cattle trade to the U.S. from Mexico was halted on Nov. 22, 2024, after a cow in the southern Mexican state of Chiapas was found to have NWS myiasis. Live cattle trade with Mexico will only resume with established NWS mitigation protocols, the holding of Mexican cattle for preventive treatments, and multiple inspections of Mexican cattle on both sides of the border.

At the time of this article, NWS has not been found in the U.S., but this harmful pest can travel on humans, vehicles, pets, livestock and even on some wildlife species — all of which increase the likelihood it could eventually enter our country.

What is NWS Myiasis?

NWS myiasis is the infestation of NWS larvae or maggots that feed on the living tissues of all warm-blooded animals, including humans, and rarely birds. Adult female flies lay their eggs, often as many as 200 to 300 eggs at a time, at the edges of wounds on animals or at the mucous membranes or body orifices. Within 12 to 24 hours the eggs will hatch, and larvae emerge to feed on living flesh by burrowing into tissue, tearing at the tissue with their hook-like mouthparts, like a screw being driven into wood and hence, their name.

The larvae can be difficult to detect for the first 24 to 48 hours, but as larvae feed on tissue, the wound enlarges and drains a serosanguineous fluid. There is severe inflammation and secondary infection as well as the stench of necrotic tissue.

Screwworm larvae pass through three stages (or instars), and they will reach maturity about five to seven days after the eggs hatch. At maturity, the larvae stop feeding and fall to the ground where they burrow and pupate to become adult flies. Adult flies live for two to three weeks in the field. Females mate only once in their lifetime.

Diagnosis, Treatment and Prevention of NWS Myiasis

Laboratory diagnosis of NWS is usually made by identification of the parasites under the microscope. NWS is a foreign animal disease that is reportable to state animal health authorities and to USDA-APHIS. The U.S. is responsible for reporting NWS to the World Organization for Animal Health and to our trading partners.

Before collecting or sending any samples from animals with a foreign animal disease, the proper authorities should be contacted. Samples should only be sent under secure conditions and to authorized laboratories. NWS can infest humans, so samples should be collected and handled with proper precautions. Larvae should be removed from the wound prior to treatment and placed in 80% ethanol for transport to the lab. Formalin should not be used.

Treatment for NWS myiasis generally includes cleaning and debriding the wounds and applying organophosphate insecticides, which are effective against newly hatched larvae, immature forms and adult flies. Carbamates and pyrethroids are also effective against larvae. Antibiotics are indicated if an infection is present. Livestock can also be protected by regular spraying or dipping with insecticides, or by subcutaneous injections of ivermectin and related compounds.

In endemic areas, animals must be inspected for screwworms every few days. NWS myiasis is often fatal in untreated cattle within 14 days.

Whenever possible, procedures that leave wounds (castration, dehorning, branding, ear tagging) should not be performed during screwworm season, and sharp objects should be removed from livestock pens. No vaccine is currently available for NWS.

Eradication from a Region

Screwworms can be managed by repeatedly releasing sterile male flies that mate with wild NWS female flies to produce unfertilized eggs. This process is called sterile insect technique and leads to a reduction in screwworm numbers and eventual eradication.

In addition, infested animals in a region are treated and their movements are controlled. Currently, the U.S. and Panama operate an NWS sterile male fly production facility in Pacora, Panama, through the Panama-U.S. Commission for the Eradication and Prevention of Screwworm, or COPEG, which produces 100 million sterile male flies per week.

The National Cattlemen’s Beef Association is committed to informing cattle producers and their veterinarians about current animal health risks and advocating for cattle health issues in Washington, D.C., on behalf of the U.S. cattle industry.

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Protecting the Herd from New World Screwworm

Protecting the Herd from New World Screwworm

Tue, 17 Dec 2024 23:49:29 GMT

by Kim Brackett, NCBA Policy Division Chair

Every cattle producer knows that pests are a challenge to our operation, but some pests are far more dangerous than others. One of the new threats to our herd comes from the New World screwworm, which is currently advancing through Central America into southern Mexico and could soon be at our border.

The New World screwworm (NWS) is a fly that has a particularly gory way of harming our cattle. Female NWS flies lay their eggs in open wounds or body orifices and when the larvae hatch, they burrow deep into the skin like a screw driving into wood. These maggots feed on cattle’s tissue, causing larger wounds as they go.

NWS flies and their burrowing larvae cause extensive damage to cattle and infestations can spread rapidly. In 1966, we eradicated screwworms in the United States through sterile insect technique. The U.S. Department of Agriculture (USDA) bred sterile male NWS flies that mated with wild female screwworms and failed to produce offspring. Eventually, these flies died out in the U.S. and now they only exist in a handful of South American countries.

Unfortunately, these flesh eating flies are now on the march north.

Since 2022, USDA’s Animal and Plant Health Inspection Service (APHIS) has confirmed the presence of New World screwworms in Costa Rica, Nicaragua, Honduras, and Guatemala. Just last month, screwworms were discovered in southern Mexico, which raised red flags for us at the National Cattlemen’s Beef Association (NCBA).

Once in Mexico, it is easy for screwworms to travel north and appear on our southern border. These flies can hitch a ride on people, livestock, or wild animals, not to mention the thousands of vehicles and cargo containers traveling through Mexico to the United States.

We know how devastating it would be if New World screwworm returned to the United States, which is why NCBA is raising the alarm now. First, we are communicating with Mexico’s cattle industry leaders so they can begin the process of screening for these flies and push for eradication efforts in their country. We are also supporting USDA-APHIS to bolster the use of sterile flies. Recently, we have been concerned that our existing sterile flies might not be getting the job done, and NCBA is pushing for more flies and better flies that will help us beat back these pests.

Although we haven’t confirmed any New World screwworms in the United States, we need you to be on high alert. New World screwworms have orange eyes, a metallic blue or green body, and three dark stripes across their backs. If you see any suspicious flies, please alert your local veterinarian, extension agent, or contact USDA-APHIS Veterinary Services.

Please also pay close attention to your cattle and watch for any open wounds or sores. If cattle exhibit irritated behavior, head shaking, you notice the smell of decaying flesh, or spot maggots in a wound, seek treatment from a veterinarian immediately. Proper wound treatment and prevention is the best way to protect your farm or ranch from a screwworm infestation. NCBA is also sharing the latest updates through our website. I encourage you to visit www.ncba.org/NWS for all the latest information on how to protect your operation.

NCBA is always on the clock to protect the U.S. cattle industry from threats like New World screwworm. Through your vigilance and NCBA’s advocacy, we can protect the United States cattle herd.

Kim Brackett is an Idaho rancher and serves as Policy Division Chair of the National Cattlemen’s Beef Association (NCBA).