New World screwworm has spread to Arizona, the third US state to report the parasite, according to Ars Technica. The USDA has identified 74 animal cases in the US since the flies re-invaded the country in June.
Arizona's agriculture department said the state's index case was a dog in Cochise County, which borders New Mexico and Mexico. A local veterinarian examined the dog on October 26 and found a back wound "heavily infested with maggots consistent with NWS characteristics," the state said.
The USDA confirmed the infection and said it is working with Arizona on a joint response. The agency recorded four new cases in domestic dogs this week, including the Arizona detection, and one case in a domestic cat in New Mexico. The total pet cases since June is 10. The USDA has also detected one case in a wild elk.
Most of the US cases have been in livestock. The report says the flies were eliminated from the country in the 1960s through releases of sterile males, and returned after a biological barrier at the Darién Gap was breached in 2022. According to Mexico's Ministry of Health, Mexico has confirmed 806 human cases since the flies reemerged, with nine deaths.
Arizona's agriculture department urged livestock owners and pet owners to monitor animals closely and report any unusual wounds consistent with NWS immediately.