Mexico has reported a new outbreak of New World screwworm (NWS) in Sabinas Hidalgo, Mexico, in the state of Nuevo Leo. This represents the furthest location to date where NWS has been detected and poses a significant threat to the livestock industry in the U.S. Sabinas Hidalgo is located on the high-traffic highway connecting Monterrey, Mexico, and Laredo, Texas, which is one of the busiest trade routes between the two countries.
The infected animal was an 8-month-old cow recently transported from an area in southern Mexico with known NWS cases to a certified feedlot in Nuevo Leon. This case highlights the critical paramount importance of controlling livestock movement and fully implementing the U.S.–Mexico Joint Action Plan on NWS. Currently, U.S. ports remain closed to cattle, bison, and the import of horses.
Since July, the U.S Department of Agriculture (USDA), in coordination with Mexican authorities, has monitored approximately 8,000 traps in Texas, Arizona, and New Mexico, analyzing more than 13,000 samples. To date, no NWS flies have been identified in the U.S. Authorities are also reviewing the new case in Nuevo Leon and preparing to release sterile flies in the affected area.
The Secretary of the USDA, Brooke L. Rollins, pointed out that securing livestock in the U.S. is a national priority. To address the threat, the USDA has developed a five-component plan to prevent the spread of NWS, protect ranchers, and ensure food security.
The primary focus is innovation. The USDA has also spent $100 million in the NWS Grand Challenge to develop new equipment, including advanced sterile fly production, improved effective traps and lures, more sophisticated sterilization techniques, and even genetically engineered flies.
The second area of concern is border protection. It is constructing a new sterile fly dispersal facility in Edinburg, Texas, which will produce 100 million sterile flies per week. A larger facility is planned in southern Texas to produce up to 300 million flies per week. The third is surveillance. The USDA continues to monitor traps, release sterile flies in Mexico, and support facility improvements to increase fly production.
The fourth focus is the issue of public awareness. The Animal and Plant Health Inspection Service (APHIS) of the USDA has offered new guidance, conducted stakeholder meetings, and published educational materials along the border to help farmers and residents detect NWS early. The fifth focus is international coordination. The USDA collaborates with Mexico and other partners, audits response efforts, encourages risk-based trapping, and effectively monitors outbreaks using SENASICA’s new tracking dashboard.
Additionally, the USDA also collaborates with agencies such as the centers for disease control and prevention (CDC), food and drug administration (FDA), department of homeland security (DHS), department of the interior (DOI), environmental protection agency (EPA), and department of energy (DOE) to support surveillance, emergency planning, veterinary care, and research. Larvae of NWS can burrow into livestock, pets, and even humans. The USDA recommends that residents be advised to inspect animals for suspicious wounds or larvae and report any findings immediately. Human infections are rare, but they should be reported by a doctor in the event of lesions. This outbreak highlights the importance of speed, international collaboration, and ongoing vigilance in preserving livestock, ensuring food safety, and protecting the American agricultural economy.
References: USDA. Mexico Confirms Case of New World Screwworm in Nuevo Leon. Published September 21, 2025. Accessed September 29, 2025. Mexico Confirms Case of New World Screwworm in Nuevo Leon
