Many MindedScrewworm reaches Arizona, its third US state, after a dog is infested
New World screwworm has now been confirmed in Arizona, the third US state affected after New Mexico and Texas. The index case was a dog in Cochise County, which borders both New Mexico and Mexico. A local veterinarian examined it on October 26 and found a back wound heavily infested with maggots consistent with screwworm. The USDA confirmed the finding and is working with the state on a joint response.
The USDA has now identified 74 animal cases since the flies re-invaded in June. Most are in livestock, but pets are increasingly involved: this week brought four new dog cases, including Arizona's, and one cat in New Mexico, for 10 pet cases in total. One wild elk case was reported the previous week. In Mexico, health authorities have confirmed 806 human infestations since the flies reemerged, with nine deaths.
The flies lay hundreds of eggs in wounds and moist orifices, and the larvae feed on living flesh. They were eliminated from the US in the 1960s by releasing sterile male flies from aircraft. A biological barrier at the Darién Gap held them back for years until it was breached in 2022, and they have since moved north through Central America.
For sustenance, this is a setback. A pest that attacks livestock puts pressure on beef supply, and that can mean higher prices and trade restrictions. It also touches health and goods. The article, as summarized to us, does not detail beef supply, prices or trade effects, so those are risks, not measured outcomes. Counts are confirmed cases only, as of October 30, 2026. Watch for whether the Arizona response contains spread, and whether cases keep moving beyond the three states.
Source: Ars Technica