03 November 2026, Austin, US: The number of confirmed New World screwworm cases in the United States has risen to 79 since the outbreak began in June, according to data reported by the U.S. Department of Agriculture on November 1. Of those, 25 remain active and 54 are now inactive, with the recent rise following a sharp drop in detections during August and September.
The parasite, whose larvae burrow into the living flesh of warm-blooded animals, has now been confirmed in Texas, New Mexico, and Arizona. The most recent case was confirmed Saturday in Doña Ana County, New Mexico, involving cattle. Other New Mexico cases in the outbreak have involved horses, cattle, and dogs. In Arizona’s Cochise County, a dog infection marked the state’s first confirmed case. In Texas, a wild elk case in Pecos County is now listed as inactive. Of the 79 total cases, 78 involve domestic animals, including livestock and pets, with one confirmed in a wild elk.
USDA’s Animal and Plant Health Inspection Service has expanded surveillance in response to the uptick, recording five wild screwworm fly detections in monitoring traps, four of them in October. The Texas Animal Health Commission and USDA have stepped up monitoring of animal movement and are urging rapid reporting of suspected cases. In September, the Food and Drug Administration issued an emergency use authorization for the flea and tick medication Capstar, along with its generic version nitenpyram, for use in treating dogs and cats affected by the parasite.
Border trade resumes in stages
The outbreak has disrupted cross-border livestock trade for more than a year. USDA suspended live cattle, horse, and bison imports from Mexico after the parasite was first detected spreading north, a move that squeezed US cattle supplies and contributed to ground beef prices reaching record highs this year. The agency has been reopening ports of entry in stages as conditions allow. Imports resumed at the Douglas, Arizona port in August and at Santa Teresa, New Mexico in September, with horse imports also resuming at Santa Teresa. The Columbus, New Mexico port was scheduled to reopen on October 26, and USDA has said it plans to reopen the Nogales, Arizona port on November 30, provided conditions for safe trade are in place by then.
The sterile insect technique, which involves releasing large numbers of sterile male flies to disrupt the parasite’s breeding cycle, was the method that originally eradicated screwworm from the United States decades ago. A sterile fly production facility reopened in Texas earlier this year as part of the renewed eradication effort, though current data on fly release volumes tied to this outbreak has not been published alongside the latest case counts.
The parasite poses no food safety risk, according to USDA, since infected animals are treated and the larvae do not contaminate meat intended for human consumption. The larger concern for the cattle industry is the economic toll of trade restrictions and the labor-intensive process of treating and monitoring affected herds across the three-state outbreak zone. Restrictions on animal movement may remain in place in affected areas even after individual cases are resolved, as officials continue surveillance to confirm the parasite has not spread further.
The outbreak traces back to a northward spread of screwworm populations through Mexico over the past two years, prompting the U.S. to invest in expanded sterile fly production capacity and tighter inspection protocols at ports of entry along the southern border.
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