New World screwworm has spread to Arizona, the third US state to report the parasite, according to the US Department of Agriculture. 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 wound "heavily infested with maggots consistent with NWS characteristics."
The USDA recorded four new cases in domestic dogs this week, including the Arizona detection, and one domestic cat in New Mexico. That brings the pet total to 10 since the flies reemerged. Most of the 74 confirmed US cases involve livestock. The USDA has also detected one case in a wild elk.
Arizona's agriculture department urged livestock owners, pet owners and animal industry partners to monitor animals closely and report any unusual wounds consistent with NWS immediately. The USDA confirmed the infection and said it is working with Arizona on a joint response.
According to the source, the flies were eliminated from the US in the 1960s through aerial releases of sterile males. A biological barrier along the Darién Gap held them back for years, but the source reports that the barrier was breached in 2022, and the flies have moved north through Central America.
Mexico's Ministry of Health has confirmed 806 human cases since the flies reemerged, with nine deaths, according to the source.