Arizona reports first New World screwworm case in dog, enforces quarantine

Arizona officials confirmed the state’s first case of New World screwworm on Wednesday after a domestic dog in Cochise County was found infested with the parasite’s larvae. Veterinarians removed dozens of maggots from the animal’s wound and sent samples to the U.S. Department of Agriculture for verification. The county borders Mexico, where the fly remains endemic, and the case marks the third U.S. state this year to report an outbreak, joining Texas and Florida.

The discovery comes as the United States battles a resurgence of a pest thought eradicated in the 1980s. The sterile‑insect technique that eliminated screwworms from the lower 48 states relied on releasing millions of sterilized male flies to outcompete wild ones. In recent years, occasional incursions have been traced to cross‑border movement of livestock, wildlife and pets from Mexico, where the fly still thrives in warm, humid environments. Climate shifts that lengthen the breeding season may also be expanding the insect’s range northward.

State and federal agencies responded quickly. The Arizona Department of Agriculture placed the affected property under quarantine and began a sweep for additional infestations on nearby farms and wildlife. The USDA’s Animal and Plant Health Inspection Service issued an alert to veterinarians, urging them to watch for similar symptoms in dogs, livestock and wildlife. In the dog’s case, treatment with ivermectin and wound care was successful, and the animal is expected to recover fully. Officials said no human cases have been reported, as the parasite does not target people.

Authorities plan to resume sterile‑fly releases along the southern border to suppress the population before it spreads further. They also announced a public‑awareness campaign, asking pet owners to check wounds for signs of maggots and to report any suspicious cases promptly. If the program succeeds, the risk to Arizona’s cattle and wildlife industries could be contained, but experts warn that vigilance will be essential to keep the parasite from re‑establishing a foothold in the United States.