Tips To Successfully Control Cattle Lice
This article was written by M. Wayne Ayers, DVM, Beef Cattle Technical Consultant, Elanco Animal Health.
For beef producers, lice infestations are as much of an emotional issue as they are an economic issue.
These parasites not only affect the well-being of cattle and the producer’s bottom line, but they can also stir up emotions. It’s disheartening to see cattle with patchy, balding hides and the sight of them incessantly rubbing and scratching on fence posts and equipment is a painful one. The hair loss caused by lice can also lead to reduced market value, adding to the emotional burden.
Since lice-infested cattle tend to scratch excessively, their attention from eating and gaining weight is easily diverted, resulting in reduced productivity and financial losses for producers. Lice infestations can cause a reduction in average daily gain (ADG) of 0.042 lb., and it’s estimated that the U.S. beef industry’s economic loss due to lice is about $428.2 million annually.1
Understanding the lice life cycle
To ensure the well-being of cattle and producer economics, controlling lice is necessary. Fighting lice can be a difficult proposition because once you have one, they can quickly multiply into more. However, understanding the louse life cycle can help determine how to break the cycle and prevent infestations.
Two types of lice can live on cattle: sucking lice and chewing lice. Sucking lice feed on the host’s blood and are most often found on the neck, dewlap, brisket, shoulder, back, tail head and down to the switch. Chewing lice feed on hair, skin, skin exudates and debris near the skin surface. They are initially found on the shoulder and backline, but as populations increase they can be found over the entire body.
Regardless of the type of lice, the life cycle of the different species impacting cattle are essentially the same. Lice have three developmental stages: egg, nymph and adult. A louse typically reaches adulthood in four to six weeks, but some may do so as quickly as three weeks in colder weather. Once lice become an issue, it’s often difficult to stop them. Assuming all eggs develop into adults, mathematically a single adult female louse in September can result in 1 million lice by January, if not controlled. The cyclical nature of lice is further illustrated below.
Successful treatment requires a proper application strategy
When challenged with a lice infestation, proper product dosage, application and timing are most important to combat these difficult pests and keep cattle productive. While producers often add on lice control when conducting other management practices, that may not be the best time to apply the product and may not provide the control needed to last the entire lice season. Instead, producers should consult with their veterinarians and consider the following to help achieve optimal lice control:
• Determine when lice are active: For lice to be active, air temperatures must be consistently below 65 degrees for around five consecutive days. This allows the animal’s skin to reach a temperature that is optimal for lice to reproduce. They reproduce most efficiently when the animal’s skin temperature is 95 degrees and 75 percent relative humidity. When the animal's skin temperature is too high, lice cannot reproduce and when the skin temperature reaches 125 degrees or higher, lice will die within an hour.2
• Dose by weight: Proper dosing is essential to realizing the maximum benefits provided by lice control products. For pour-ons, dosing generally is determined by an animal’s body weight. Knowing the proper weight range can help determine the appropriate dosage needed.
• Follow label application directions: When treating cattle for lice, it’s important to provide coverage to the animal’s entire body as lice are not necessarily localized to any one area. This is especially important for chewing lice because they do not feed on the animal's blood; they need to walk through the product for it to be effective. Be sure to read the product label and follow the application directions.
• Don’t forget the eggs: Most lice control products only kill the adults but not the eggs. It’s recommended to give a second application two to three weeks following the first one to kill the adults that hatch from the original eggs and ultimately halt the lice life cycle. Failure to apply this second treatment can result in reproductive adults that can reinfest already-treated cattle. To help avoid reinfestations and save on the labor of having to perform a second application, consider the use of a lice product with an insect growth regulator (IGR), which requires only one application to kill the adults and eggs.
• Separate animals: After animals are treated, it’s critical to keep them separate from animals that either have not been treated or for those with an unknown treatment status. Failure to separate animals can lead to reinfestation of the entire herd, negating any previous control efforts.
• Consider an early-season knockdown: While broad-spectrum pour-on dewormers (endectocides) should only be used when internal parasites are the primary target, they can provide added benefits for lice. Treating with an endectocide in the fall can provide an added knockdown for early lice infestations, keeping them at bay until winter treatment with a lice control product.
- Evaluate mid-season: Even if a product promises full-season control, if it’s applied too early or with poor technique, underdosed or re-exposure occurs, it may be necessary to retreat during winter, especially in colder areas with longer lice seasons.
As we continually navigate solutions, it becomes clear that a comprehensive approach to lice control is essential, one that not only safeguards the economic interests of cattle producers but also acknowledges and alleviates the emotional burden. To learn more about a strategic lice control protocol, talk with your veterinarian or Elanco technical representative.
References:
1 Byford RL, Craig ME, Crosby BL. A review of ectoparasites and their effect on cattle production. J Anim Sci. 1992:70:597-602
2 Matthysse J. Cattle lice: Their biology and control. Cornell Univ Agric Exp Stat Bull. 1946:832:3–67.
