Arizona officials are bracing for the potential return of the New World screwworm, a fly whose larvae burrow into and feed on the living flesh of warm-blooded animals.
University of Arizona scientists and state agriculture officials are sounding the alarm for livestock producers, pet owners and residents to remain vigilant against screwworm as federal authorities prepare to reopen a key trade crossing in Douglas next month.
The U.S. Department of Agriculture announced it will begin lifting its suspension on Mexican cattle imports starting August 24, with the initial reopening centered at the border crossing in Douglas.
The suspension was originally imposed due to a massive screwworm outbreak in Mexico that has now spread to 29 of the country’s 32 states, with nearly 1,800 active cases, the Associated Press reported.
U.S. authorities said imports of Mexican cattle will be subject to compliance with a joint action plan, and the animals will undergo inspection in the U.S. to prevent the entry of screwworm larvae.
Here’s what Arizonans need to know about New World screwworm, ahead of the border reopening for cattle trade.
What is New World screwworm?
Unlike common maggots that feed on dead tissue, the New World screwworm is a highly destructive parasite whose larvae feed exclusively on the living tissue of warm-blooded animals.
The fly lays eggs in even the smallest open wounds, which can hatch into flesh-eating larvae in as little as 12 to 24 hours.
New World screwworm does not discriminate on what animals it’s willing to infest, according to veterinarian Casey Locklear.
"It will infest any warm-blooded animal: livestock, wildlife, cats and dogs. It can even infest people,” she said.
While Tthe pest was officially eradicated from the U.S. in the 1960s, according to the USDA.,But recent detections in Texas and New Mexico have placed Arizona on the defensive.
Southern Arizona and the surrounding borderlands are considered high-risk zones because the fly thrives in warmer climates.
How to protect your pets from New World screwworm
The Arizona Livestock Incident Response Team announced it is coordinating with local agriculture experts and veterinarians to build a safety net for the industry.
Authorities emphasize that early detection is critical. Animal owners should inspect for non-healing wounds and report any suspected cases immediately to diseasereporting@azda.gov.
To support local monitoring, free sampling kits are now available at local Extension offices.
A free, full-day New World screwworm preparedness workshop is scheduled for August 15 in Pima County to provide hands-on diagnostic training for producers and veterinarians.
The University of Arizona announced it secured a $3.74 million USDA investment on June 30 to strengthen the state’s coordinated detection and response efforts.
Pima County residents can also pick up free sampling kits at their local Extension office to allow for immediate specimen collection if an infestation is suspected during routine animal checks.
What are the signs of a New World screwworm infestation?
Locklear said that while the parasite is not directly contagious between animals, it is spread rapidly by flies.
Experts urge Arizonans to inspect their animals daily. Key warning signs of an infestation include:
- An unexpected or enlarging wound.
- Wounds with unusual discharge or a foul odor.
- Glistening movement or visible maggots within a wound.
Pet owners are encouraged to maintain active parasite coverage, such as flea and tick prevention, to minimize the small wounds that attract the flies.
