USDA Finds News Cases of a Flesh-Eating Cattle Parasite Called Screwworm

New World screwworm cases continue to increase in the United States, with three additional infections confirmed in Texas and New Mexico. The pest, a flesh-eating fly larva that infests open wounds in animals, poses a serious threat to cattle, wildlife, pets, and occasionally humans. There are now five confirmed cases: three calves and a goat in Texas, plus a dog in New Mexico. Officials have established 12-mile quarantine zones around affected areas and are conducting investigations to determine whether local fly populations are present.

The USDA and cattle industry have been preparing for a potential outbreak since screwworm was detected in Mexico in late 2024. Current control efforts include releasing sterile male flies, a proven technique that helped eradicate the pest from the U.S. decades ago. Additional sterile fly production and a proposed $750 million fly-breeding facility in Texas are planned. While experts expect more cases to be discovered, they caution that increased detection may reflect heightened surveillance rather than rapid spread. Ranchers are being urged to closely monitor livestock and report suspected infestations immediately.