On Sept. 21, 2025, Mexico’s National Service of Agro-Alimentary Health, Safety, and Quality (SENASICA) confirmed a new case of New World screwworm (NWS) in Sabinas Hidalgo, located in the state of Nuevo León, less than 70 miles from the U.S.-Mexico border.

This is now the northernmost detection of NWS during this outbreak, and the one most threatening to the American cattle and livestock industry. Sabinas Hidalgo is located near the major highway from Monterrey, Nuevo Leon, to Laredo, Texas, which is one of the most heavily trafficked commercial thoroughfares in the world. Currently, U.S. ports remain closed to imports of cattle, bison, and horses from Mexico.

Since July, USDA alongside Mexico, has been actively monitoring nearly 8,000 traps across Texas, Arizona, and New Mexico. To date, more than 13,000 screening samples have been submitted, with no NWS flies detected. USDA is analyzing all new information related to the recent case in Nuevo León and will pursue all options to release sterile flies in this region as necessary.

The USDA urges residents on the southern border to check their pets and livestock for signs of NWS. Look for draining or enlarging wounds and signs of discomfort. Also look for screwworm larvae (maggots) and eggs in or around body openings, such as the nose, ears, and genitalia or the navel of newborn animals.

If you suspect your animal is infected with screwworm, contact your state animal health official or USDA area veterinarian immediately.