Federal officials have confirmed 116 cases of New World screwworm across the Southwest, up nearly 55 percent from the total recorded a week earlier on October 29. Department of Agriculture data shows 56 active cases and 60 inactive cases. An inactive designation means mitigation is no longer required for the individual animal and does not necessarily mean the surrounding area is free of the parasite.
Of these, 64 of the 116 cases were confirmed in the past 30 days. Recent detections include cattle in Hudspeth and Mitchell counties, Texas, a horse in Greenlee, Arizona and more cattle in Eddy and Otero counties, New Mexico. There is also a reported case in a domestic dog in Sierra county, New Mexico.
Cases have also been detected in fly traps. These findings are tracked separately from animal cases but provide additional evidence of the parasite's presence in the region. New World screwworm is a parasitic fly whose larvae infest the wounds of living, warm-blooded animals, feeding on living tissue.
It can affect livestock, wildlife, pets and, more rarely, people. The USDA describes it as a serious threat to livestock and wildlife, although it currently assesses the risk to people in the United States as very low and says the outbreak is not a food-safety issue. Newsweek reached out to the USDA via email for comment.
Earlier this year, the department told Newsweek: “USDA is responding aggressively to the current outbreak through a fully coordinated effort that includes trapping, animal inspections, wildlife surveillance, sterile insect releases, and extensive public outreach. Together, these tools isolate cases and break the pest’s lifecycle to help prevent further spread.” New World screwworm was considered eradicated from the U.S. in 1966 following a campaign using the sterile insect technique, in which large numbers of sterile male screwworm flies were released. When wild females mated with the sterile males, they produced no viable offspring, progressively suppressing the population.
The U.S. and partner countries subsequently pushed established screwworm populations south through Mexico and Central America. In 2023, Panama and Costa Rica identified a renewed outbreak. The parasite subsequently spread through every country in Central America and into Mexico, areas where it had previously been controlled.
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