A New World screwworm case has been confirmed about 197 miles from the U.S.–Mexico border — the first reported detection in the Mexican state of Tamaulipas. The case was identified in a six-day-old calf, according to Mexico’s animal health agency SENASICA.
While NWS has not been detected in the United States, the northward movement of the pest has U.S. and state officials emphasizing vigilance because the parasite can cause severe tissue damage and death in livestock if untreated. Earlier in December, NWS was detected approximately 120 miles south of the Texas border. In September, a case was detected less than 70 miles from the U.S.-Mexico border.
The U.S. Department of Agriculture’s latest update reiterates that the U.S. remains free of NWS, but is monitoring detections in Mexico and Central America and posting updates through its official response hub.
Texas Agriculture Commissioner Sid Miller said continued detections near Texas are a reminder of the threat NWS poses to the state and again emphasized the importance of eradication tools, particularly sterile fly programs. “I will continue to support and advocate for federal efforts to expand sterile fly production and infrastructure, because this proven strategy is key to the long-term eradication of New World screwworm.”
Reuters reported a second case in two days in Mexico, involving a goat in the State of Mexico. According to the Reuters report, Mexico has recorded thousands of cases since late 2024, with hundreds active, and U.S. restrictions on livestock movement from Mexico have remained in place as authorities work to prevent the pest from reaching U.S. herds.
In recent weeks, the U.S. Food and Drug Administration conditionally approved a chewable tablet product for treatment of NWS infestations in dogs and puppies, and the agency has also announced conditional approvals related to cattle prevention and treatment tools, adding options for veterinarians and producers as surveillance continues.
USDA encourages livestock owners to stay informed through screwworm.gov, follow biosecurity guidance, monitor animals for wounds, and contact a veterinarian if infestations are suspected.
