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.
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.
The New World screwworm fly is threatening the $113 billion U.S. cattle industry for the first time in more than a half century, with an infestation from its flesh-eating larvae confirmed in south Texas.
The infestation was discovered in a single 3-week-old calf in La Pryor, Texas, about 100 miles (161 kilometers) southwest of San Antonio and 50 miles (80 kilometers) from the U.S.-Mexico border. Federal and state officials had been working to keep the parasite from reaching Texas, home to $17 billion worth of the nation's cattle, making it the industry's No. 1 state.
The U.S. Department of Agriculture on Friday announced a second confirmed case found in a one-month-old calf in Zavala County, Texas, about 5.6 miles (9 kilometers) from the first case.
The deadly flies were detected in Mexico late in 2024, after years of being contained at the southern end of Panama.
The fly was an annual warm-weather scourge of cattle ranchers from at least the 1930s through the 1960s, until the U.S. eradicated the pest by breeding sterile male flies and dropping swarms of them from planes to mate with wild females. The USDA said the most recent case was the first in Texas since 1966.
