USDA to Release Sterile Flies in Texas to Counter NWS Parasites

The northernmost active NWS case in Mexico has been detected roughly 200 miles from the U.S.–Mexico border.

Livestock in pens before being exported to the United States, at the Chihuahua Regional Livestock Union facility, outside Ciudad Juarez, Mexico, on Feb. 10, 2025. Jose Luis Gonzalez/Reuters

The Animal and Plant Health Inspection Service (APHIS) will start dispersing sterile male flies near the U.S.–Mexico border and in parts of Texas in an attempt to prevent swarms of New World screwworm (NWS) parasites from advancing into the United States from Mexico, APHIS said in a Jan. 30 statement.

APHIS is an agency under the Department of Agriculture (USDA). To counter NWS parasites, the USDA has been dispersing 100 million sterile flies per week in Mexico.