Illegal movement of horses across the U.S.-Mexico border is raising concerns about a potential gap in efforts to prevent New World screwworm from reaching American livestock.
A Reuters investigation found horses and other livestock are being moved illegally across parts of the Texas-Mexico border, bypassing the normal animal-health inspection system.
The practice has taken on new significance as U.S. officials work to prevent the flesh-eating parasite from spreading northward.
New World screwworm larvae infest wounds in warm-blooded animals and can cause serious injury or death if untreated.
The pest poses a particularly significant threat to cattle production.
USDA has made screwworm prevention a major component of its livestock-health strategy as the parasite has moved through Mexico.
The department says its response includes surveillance and other measures designed to protect the U.S. cattle supply.
Animals crossing the border outside official inspection channels complicate those defenses because infected livestock could potentially avoid veterinary screening.
The threat comes as ranchers are already dealing with tight cattle supplies and high production costs.
