The USDA is investigating possible screwworm infections in South Texas after samples were taken from two calves in La Pryor. An official suspects the New World screwworm has reached the US, though tests remain unconfirmed. The larvae found in the calves resemble screwworm larvae, according to images reviewed by authorities.

Screwworms were eradicated from the US in the 1960s using the Sterile Insect Technique, which involves releasing sterile male flies to prevent mating. The USDA maintained a biological barrier in Panama, but breached in 2022, allowing the parasites to move north. This threatens livestock and could cause significant economic damage if established in the US.

In response, the US has expanded surveillance and is building a $750 million sterile fly production facility in South Texas. The USDA currently disperses 100 million sterile insects per week along the US-Mexico border. The agency faces containment challenges as the screwworm population advances further north.