New World Screwworm Confirmed in Nuevo Leon

Mexico's National Service of Agro-Alimentary Health, Safety, and Quality (SENASICA) confirmed yesterday 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 area in Mexico is located near Laredo, Texas, one of the world's busiest commercial thoroughfares.

NWS, a flesh-eating parasite, is endemic in the American tropics, including countries in South America. The previous northernmost detection was reported in July 2025, in Veracruz, approximately 370 miles south of the Texas border.

As of September 22, 2025, this confirmation is now the northernmost detection of NWS during this outbreak, and the one most threatening to the American cattle and livestock industry.

"Protecting the United States from NWS is non-negotiable and a top priority of the Trump Administration," said U.S. Secretary of Agriculture Brooke L. Rollins, in a media release.

"This is a national security priority. We have given Mexico every opportunity and every resource necessary to counter NWS since announcing the NWS Bold Plan in June 2025."

"Nevertheless, American ranchers and families should know that we will not rely on Mexico to defend our industry, our food supply, or our way of life. We are firmly executing our five-pronged plan and will take decisive action to protect our borders, even in the absence of cooperation."

"Furthermore, we will pursue aggressive measures against anyone who harms American livestock."

Preliminary reports from SENASICA indicate that the affected animal—an 8-month-old cow—had recently been moved to a certified feedlot in Nuevo León from a region in southern Mexico with known active NWS cases.

The potential link to animal movement underscores the non-negotiable need for Mexico to implement and fully comply with the U.S.–Mexico Joint Action Plan for NWS in Mexico.

Currently, U.S. ports remain closed to imports of cattle, bison, and horses from Mexico.

Since July, the 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.

In addition, USDA will soon release a significant plan to help rebuild the American cattle supply, incentivizing our great ranchers and driving a full-scale revitalization of the American beef industry.

The USDA serves as the lead coordinating agency, deploying advanced surveillance systems, ramping up domestic preparedness, investing in innovative detection, control, and response tools and strategies, and supporting robust cross-border response efforts in Mexico and Central America to combat the pest and prevent its spread to the United States.

NWS myiasis is typically a disease of livestock, but it can also affect humans, according to the U.S. CDC and Food and Drug Administration (FDA). 

"Our priority is to safeguard both animal health and the nation's food supply," said FDA Commissioner Marty Makary, M.D., M.P.H., in a previous press release.

According to the Cattle Association, an NWS outbreak in Texas could cost over $1 billion in annual damages to livestock.

There is no medication to treat NWS; prevention and quick removal are key. Furthermore, no NWS vaccine exists for humans.