Five New World Screwworm Cases Confirmed in Texas and New Mexico

U.S. officials confirmed three new cases of the New World screwworm on June 9, raising the total number of domestic detections to five. The parasite is a fly whose larvae burrow into open wounds of warm-blooded animals and feed on living tissue. The five confirmed cases involve two calves in Zavala County, Texas, one calf in La Salle County, Texas, one goat in Gillespie County, Texas, and one dog in Lea County, New Mexico.

Parasite The New World screwworm was eradicated from the United States in the 1960s and from Mexico in the 1970s. New detections began appearing in Panama, Costa Rica, Nicaragua, and Honduras in October 2024, and the first U.S. case was reported in Texas on June 3.

The fly lays eggs on wounds as small as a tick bite. The hatched larvae burrow into flesh, causing myiasis that can be fatal if untreated. The parasite does not infect meat or fruit.

Greg Abbott declared a state of disaster on June 5.

The Canadian Food Inspection Agency announced a ban on Texas livestock imports the same day. The U.S. Department of Agriculture is expanding sterile-fly production facilities in Mexico and Texas and is releasing sterile flies over affected areas in Mexico. A new facility in Edinburg, Texas, is scheduled to open in November 2027 with capacity for 300 million sterile flies per week.

Beef prices have risen steadily since December 2020 amid strong demand and the smallest U.S. cattle herd in 75 years, according to the American Farm Bureau Federation. Officials have not yet quantified any additional price effects from the current detections.