The United States Department of Agriculture (USDA) recently reported the first (two) cases of New World screwworm (NWS) in the United States since its eradication from the country in 1966.

This serious and potentially impactful parasite of livestock, pets, wildlife and, in rare cases, people, was detected in two calves in Zavala and La Pryor Counties, Texas. The first case was reported on June 3^rd, 2026.

Officials are monitoring the situation closely and instituting a concerted response involving increased surveillance, quarantines, livestock movement restrictions, trapping of adult NWS flies and the release of sterile NWS flies designed to help control the parasites spread and to ultimately eradicate it from the US once again.

The adult NWS fly lays its eggs into wounds in the skin of susceptible animals, and its developing larvae feed upon the healthy tissue of their host. Infestation can occur in any warm-blooded animal and can range in severity from mild to potentially life-threatening.

Cats are at risk of infestation, particularly if they are allowed outside; and owners (particularly those near the US/Mexico border) are advised to monitor their cats closely for wounds (cuts, surgical sites, bite wounds) that grow rapidly, are accompanied by foul-smelling discharge, and/or that demonstrate visible larvae (worm-like organisms) in or around the wound. Affected cats may show behavioral signs such as excessive licking or scratching at an infested wound.

If any of these signs are observed, owners should contact their veterinarian immediately to assure prompt stabilization and antiparasitic treatment. The Food and Drug Administration (FDA) recently issued an emergency use authorization for lotilaner (brand name Credelio CAT, currently approved as a flea/tick preventative in cats) as a treatment for NWS infestation in cats.

All confirmed cases should be reported to the USDA. You can find out more about this important feline health threat by visiting:

New World screwworm information