Arizona’s First New World Screwworm Case Confirmed

USDA’s Animal and Plant Health Inspection Service (APHIS) has confirmed a case of New World screwworm in a dog in Cochise County, Ariz. The case marks the first official detection of the flesh-eating parasite in the state since it was eradicated from the U.S. in the 1960s.

According to federal officials, diagnostic samples taken from the infected dog were tested and confirmed by the APHIS National Veterinary Services Laboratories (NVSL) in Ames, Iowa. The Arizona Department of Agriculture (AZDA) reported that a local veterinarian initially examined the dog after discovering an infested wound on its back consistent with screwworm infestation. In response, APHIS confirmed it is “working closely with the Arizona Department of Agriculture on a joint response.”

State animal health officials emphasize proactive planning in border counties has positioned the state to react quickly.

“We have been preparing for this possibility for a long while and are acting swiftly,” says Arizona State Veterinarian Dr. Ryan Wolker. “Because of the extensive outreach, coordination and surveillance already in place, Arizona producers, veterinarians and pet owners know what to look for and how to report suspected cases. That preparation is allowing us to move quickly to protect animal health in the state.”

Rapid Containment: 20-km Zone and Sterile Flies

APHIS and Arizona animal health authorities have begun implementing immediate response activities outlined in the APHIS NWS Response Playbook, including:

• Establishing an infested zone: Designating a 20-km (12.4 mile) infested zone around the latest detection and implementing animal movement controls for the area.
• Targeted trapping and surveillance: Increasing live animal surveillance and trapping.
• Sterile insect technique (SIT): Releasing millions of sterilized male NWS flies to break the reproductive cycle.
• Producer and veterinary outreach: Implementing targeted outreach to local producers, veterinarians and communities.

Cochise County’s Strategic Containment Role

Cochise County holds strategic significance in screwworm containment. Located directly along the U.S.–Mexico border and home to the Douglas Port of Entry, the county previously operated a USDA sterile fly facility between 1963 and 1983.

Federal officials recently invested $25 million toward expanding sterile fly dispersal operations and infrastructure in Douglas, Ariz., to defend livestock supply chains against the pest.

Secretary of Agriculture Brooke Rollins visited Nogales, Ariz., Oct. 27 for a firsthand look at the work being done to protect farmers, ranchers and food supply. The Nogales, Ariz., port will reopen for cattle on Nov. 30, if conditions continue to support safe trade and required inspection arrangements and infrastructure are in place.

Surge in Detections: October Cases Spike

As of Oct. 28, there are 18 active NWS cases in the U.S. Since the first case in June, there have been 70 recorded cases across three states — Texas, New Mexico and now Arizona. Looking at the monthly totals, there were only three recorded in September compared to 19 thus far in October — the largest number of cases per month since the first case was found in Texas.

What Ranchers and Pet Owners Must Watch For

USDA urges livestock producers and pet owners throughout the region to remain on high alert and inspect herds and working animals daily. Navel cords of newborn calves, branding sites, ear-tag punctures, dehorning or castration wounds, and tick bites are primary entry points for screwworm flies to lay eggs.

The agency instructs animal caretakers to check daily for:

• Draining or enlarging wounds.
• Maggots or egg masses in wounds.
• Signs of discomfort or irritability.
• Lesions around body openings, including the ears, nose, genital area and umbilicus.

Reporting and Resources

Prompt reporting is critical to containing NWS. Anyone who suspects an infestation should immediately contact a veterinarian, state animal health official or USDA.

• Suspect Cases: Producers and pet owners can report potential infestations directly to their veterinarian, through the USDA NWS reporting portal, or by contacting the Arizona Department of Agriculture directly.
• Status Dashboard: A complete, daily-updated list of confirmed NWS cases across the country is available on USDA’s public dashboard at screwworm.gov under “Current Status,” updated daily at 6 p.m. ET.
• More Information: Detailed guidance regarding biosecurity protocols, treatment options, movement restrictions and eradication efforts can be found at screwworm.gov and through USDA-APHIS updates via @Screwworm_RR.

Your Next Reads:

• Screwworm Spreads to Wildlife: USDA Urges Producer Vigilance as Cases Increase
• Third Gate to Open Oct. 26: Columbus, N.M., Port Set to Resume Cattle Trade