2nd New World screwworm case in Cochise County confirmed by Arizona agriculture officials

Authorities have confirmed a second New World screwworm (NWS) case in Cochise County, this time affecting a domesticated horse with no known travel history.

Arizona’s first confirmed case came on Oct. 26, about 45 miles away from the second case, when a veterinarian discovered a dog in Cochise County was infected.

With the additional case, a new Infected Zone will be established, ranging the mandatory 20-kilometer (12.4 miles) radius around the affected area.

No animals are allowed to leave the Infected Zone until movement restrictions are lifted, per the United States Department of Agriculture’s New World screwworm playbook. Additionally, self-inspection is suspended while the Infected Zone is active.

The Arizona Department of Agriculture stresses the importance of vigilance among livestock owners, horse owners, veterinarians, hunters and pet owners. The AZDA also encourages those taking care of animals to inspect wounds closely and immediately report any unusual wounds that appear to be infected by maggots consistent with NWS.

The AZDA is working with the USDA, neighboring states and Mexican counterparts to support regional NWS response efforts.

What is a screwworm?

The screwworm — actually a fly larva that burrows into the flesh of livestock, pets and even humans — has threatened the $113 billion U.S. cattle industry.

Containment efforts have cost jobs and trade in border communities, cutting off a source of cattle as the U.S. struggles to rebuild drought-depleted herds. Reopening crossings could help ease that squeeze, although experts caution that shoppers shouldn’t expect quick relief on beef prices.

The parasite was an annual livestock scourge before being largely eradicated in the U.S. in the 1960s. It reappeared in Mexico in 2024, and the first confirmed U.S. case was in Texas in June.

More than 60 cases have been confirmed in Texas and New Mexico, with infestations of cattle, sheep, goats, horses and dogs. Last week, the first case in U.S. wildlife was confirmed after a hunter found screwworm in an elk.

What should people do if they discover New World screwworm?

For pets, livestock or sheltered animals: Suspected cases should be reported immediately to AZDA by emailing diseasereporting@azda.gov or calling 602-542-4293 during business hours (Monday through Friday, 8 a.m. to 5 p.m.).

For wildlife: Hunters and outdoor enthusiasts who spot infected wildlife should contact the Arizona Game and Fish Department at 623-236-7201. Callers should note the approximate GPS coordinates of the sighting.

The Associated Press and KTAR News 92.3 FM’s David Veenstra contributed to this report.

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