Second flesh-eating screwworm case confirmed
- By Reuters -
- Jun 06, 2026
LA PRYOR, Texas/MEXICO CITY: A second case of the flesh-eating screwworm parasite was confirmed in Texas by the U.S. Department of Agriculture on Friday, emerging just miles from where the first U.S. detection in decades was reported this week.
The new case in Zavala County was detected on a ranch 5.6 miles (9 km) from the first positive case of screwworm in Texas, which the USDA confirmed on Wednesday.
The infection, which the USDA said was in a one-month-old calf, was reported earlier on Friday by Reuters, citing sources.
The USDA discovered the second infestation “after testing a number of suspect cases,” the department’s Animal and Plant Health Inspection Service said in a press release.
APHIS and Texas Animal Health Commission officials are continuing to “collect and test other samples from the surrounding area which have come back negative,” it said.
Friday’s case and the initial detection in nearby La Pryor, a town roughly 30 miles (50 km) northeast of the U.S.-Mexico border, have dealt a setback to U.S. cattle ranchers, who have been preparing for the arrival of the pest as it has moved north through Mexico over the past year.
Screwworms are parasitic flies that deposit eggs in open wounds or mucous membranes of warm-blooded animals. After hatching, the larvae penetrate living tissue, feeding on the host and potentially causing fatal damage if not treated.
An outbreak in U.S. border states in the 1960s devastated wildlife and inflicted heavy financial losses on ranchers.
A widespread resurgence now could pose a significant economic threat in Texas, the country’s largest cattle-producing state, through animal deaths as well as higher labor and treatment costs.
To limit the risk, Washington has kept the U.S.-Mexico border closed to live cattle imports for more than a year and has spent millions of dollars to curb the pest’s northward spread, including funding sterile fly production, expanding trapping programs and stepping up livestock monitoring.