Mexico Confirms New Screwworm Case Near US Border, Raising Alarm for Cattle Industry

New Screwworm Case Detected in Northern Mexico

Mexico's National Service of Agro-Alimentary Health, Safety, and Quality (SENASICA) confirmed a new case of New World screwworm (NWS) on September 21 in Sabinas Hidalgo, Nuevo León. This location is less than 70 miles (113 km) from the U.S.-Mexico border, marking the northernmost detection of NWS during the current outbreak and escalating concerns for the American cattle and livestock industry.

Understanding the Threat of New World Screwworm

The New World screwworm, scientifically known as Cochliomyia hominivorax, is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals. This flesh-eating infection, known as myiasis, can cause severe wounds and often leads to death if untreated. While primarily affecting livestock and wildlife, human cases are rare. The pest was successfully eradicated from the United States in 1966 through a massive USDA-led program, but a resurgence in Central America has seen it steadily advance northward through Mexico. An outbreak in Texas alone could cost producers an estimated $732 million per year, with a total state economic loss of $1.9 billion, according to USDA estimates.

Details of the Current Infestation and Spread

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 strategic location of Sabinas Hidalgo, near the major highway connecting Monterrey, Nuevo León, to Laredo, Texas, is particularly concerning due to its status as one of the world's most heavily trafficked commercial thoroughfares. The previous northernmost detection was reported on July 9 in Veracruz, approximately 370 miles farther south.

Heightened US Response and Collaborative Measures

In response to the escalating threat, the U.S. Department of Agriculture (USDA) has intensified its efforts. U.S. ports remain closed to imports of cattle, bison, and horses from Mexico since the July 9 case. U.S. Secretary of Agriculture Brooke L. Rollins stated, 'Protecting the United States from NWS is non-negotiable and a top priority of the Trump Administration. This is a national security priority.' The USDA is executing a five-pronged plan, which includes:

• Border Protection: Construction of a domestic sterile fly dispersal facility at Moore Air Force Base in Edinburg, Texas, capable of dispersing up to 100 million sterile flies per week. Planning is also underway for a domestic sterile fly production facility in Southern Texas with a projected capacity of 300 million sterile flies per week.
• Surveillance: Active monitoring of nearly 8,000 traps across Texas, Arizona, and New Mexico, with over 13,000 screening samples submitted to date, none of which have detected NWS flies.
• Cross-border Action: Continued dispersal of 100 million sterile flies per week in Mexico, sourced from the COPEG facility in Panama, and support for renovating a production facility in Metapa, Mexico.
• Innovation: A $100 million initiative through the NWS Grand Challenge to develop new technologies for enhanced sterile fly production, advanced traps, lures, and therapeutics.

The National Cattlemen's Beef Association (NCBA) CEO Colin Woodall expressed concern, stating, 'It is extremely concerning for the American cattle industry that New World screwworm has moved so far north in Mexico and now is just 70 miles from the border.' The USDA is urging border ranchers and residents to remain vigilant and report any suspected cases immediately.