WASHINGTON, D.C. – As more cases of New World Screwworm (NWS) are reported, the U.S. cattle industry is bracing for an increased likelihood of infestation reaching domestic cattle herds.
Within a two-day span, Mexico has confirmed two cases of NWS, including one detected in a six-day-old calf in the northern state of Tamaulipas.
Reported on Thursday, January 1, 2026, the parasite was detected and treated in a goat in the State of Mexico, which borders capital Mexico City, the Mexican ministry said, adding that the 20 other animals at the site tested negative and were given preventive treatment.
Earlier, on December 31, the ministry reported a case in a six-day-old cow calf in the northern state of Tamaulipas, also the only positive case on site.
Mexico has so far reported a total of 13,106 cases since November of 2024, according to government data through December 31, 2025. Of those cases, 671 were active currently.
The southern border state of Chiapas has the most confirmed cases, followed by Oaxaca, Veracruz and Yucatan.
In 2023, Panama and Costa Rica identified an outbreak of NWS. Since that time, all countries in Central America and Mexico, where NWS was previously controlled, have identified cases in animals and people.
Mexico has been working to contain the outbreak of the screwworm, which has spread northward from Central America, disrupting the livestock and beef industries of both the U.S. and Mexico.
Because of the outbreak, the U.S. has kept its southern border largely closed to Mexican livestock since March 2025 when the NWS outbreak escalated, leading to increased concerns and containment efforts by the USDA, with confirmed cases in Mexican states prompting import suspensions for livestock.
Although U.S. officials say the pest has not yet breached the U.S. border, it threatens $1.8 billion in damage to Texas’ economy alone, according to a U.S. Department of Agriculture estimate.
To support a swift response if NWS reaches Texas, producers located on the southern border and travelers from NWS-affected areas should closely monitor animals for signs and promptly report suspected cases of NWS.
Screwworms are parasitic flies. Females lay eggs in wounds. Their larvae burrow through the flesh of animals, eventually killing the host if left untreated.
