USDA has detected the first wild New World screwworm fly since the parasite was found in US livestock in June, Bloomberg reported. The fly was caught in Brewster County, Texas, in one of the more than 100 screwworm fly traps USDA operates along the border. No cases have been found in wild animals.
The US has recorded about 50 screwworm cases since June. Two are active: a horse in Presidio County, which borders Brewster County, and a case in Grant County, New Mexico.
USDA places its traps “just outside of infested areas to avoid capturing sterile flies and better pinpoint where wild flies may be moving,” the agency said. USDA releases sterile male flies that mate with wild females to curb reproduction. The sterile flies now come from smaller facilities in Panama and Mexico. A large sterile fly production facility in Texas is not scheduled to open until April or May 2027.
The catch comes days after USDA reopened the Santa Teresa, New Mexico, port to Mexican cattle. The US halted livestock imports from Mexico after screwworm reached that country in 2024 and began a phased reopening of ports in late August.
Paolo Tizzani, senior veterinary epidemiologist at the World Organization for Animal Health, told Bloomberg that “surveillance results cannot by themselves establish that transmission has completely stopped.”
