Southwest Livestock Haulers Warned: Screwworm Cases Are Rising

New World screwworm cases are increasing across the Southwest, prompting additional inspections, movement requirements and permits that could affect livestock haulers operating in Texas, New Mexico and Arizona.

Cases Increase Across Southwest

Federal officials have reported 116 confirmed animal infestations across the three states, an increase of nearly 55% from the total recorded on Oct. 29. Other updates cited by state and federal officials have placed the total at 124 or 126 confirmed animal cases as reporting has continued.

Most confirmed infestations have involved domestic animals, including livestock and pets. Two cases involved elk in Pecos and Jeff Davis counties in Texas. New Mexico has reported at least 42 animal infestations, while cases have also been identified in Texas and Arizona.

New Mexico officials have expanded infested zones across much of the southern portion of the state after cases tripled in recent days. Texas has also imposed restrictions in portions of 14 counties. The USDA has recorded a sixth wild-fly trap detection as officials continue monitoring the parasite.

Livestock Haulers Face Added Requirements

Livestock carriers traveling through affected areas could encounter increased inspections, permits and other animal-movement requirements. Requirements may vary by state, county and the type of animals being transported.

The southern livestock ports, which closed in May 2025, began reopening to livestock in August after reported infections declined. However, the continued rise in confirmed cases has kept additional screening and border controls in place.

Cattle entering the United States from Sonora, Mexico, undergo dipping treatments, a holding period and pre-entry examinations by USDA personnel. Officials also use trained dogs to conduct sweeps for signs of screwworm before animals enter the country.

USDA Expands Response

The USDA is hiring 228 workers in Texas to expand sterile-fly production. The sterile-insect program is intended to help suppress the screwworm population by releasing sterile flies that reduce reproduction.

New World screwworm larvae infest wounds in warm-blooded animals. The parasite can affect livestock, horses, pets and wildlife, creating additional handling and inspection concerns for producers and carriers moving animals through affected regions.

Economic Impact

The parasite was previously eliminated from the United States, but cases have returned in the Southwest. A case involving a dog in Lea County, New Mexico, was identified in June.

During the 1950s, livestock producers in the U.S. Southwest lost as much as $100 million annually to New World screwworm. That amount would exceed $1 billion in today’s dollars.