Screwworm has been found in U.S. wildlife for the first time, and in a beef cow in southern New Mexico
The flesh-eating parasite, eradicated from the United States decades ago, has been moving north through Mexico. Officials announced both detections on October 21 and are widening surveillance and fly trapping.
Key takeaways
- USDA confirmed screwworm in an elk on a game ranch in Pecos County, Texas, the first detection in U.S. wildlife.
- New Mexico confirmed a case in a beef cow in Otero County, the state's fifth since the pest returned this summer.
- Animals inside a 20-kilometer infested zone must be inspected, and treated if needed, before they move.
Federal and state officials confirmed two new New World screwworm detections on October 21, including the first ever found in U.S. wildlife. The U.S. Department of Agriculture said the parasite was found in an elk on a game ranch in Pecos County, Texas, after a hunter killed the animal, Reuters reported. The same evening, the New Mexico Department of Agriculture confirmed an infestation in a beef cow in Otero County.
What is screwworm, and why does it matter?
Screwworm flies lay eggs in open wounds, and the larvae feed on living tissue. The pest was eradicated from the United States decades ago through the release of sterile flies, but it has spread north from Central America through Mexico. The U.S. halted livestock imports from Mexico for more than a year, which contributed to record beef prices, before a phased reopening began in August.
What happens around the new cases?
Officials set an infested zone with a radius of at least 20 kilometers, about 12.4 miles, around the New Mexico cow. Animals inside it must be inspected, and treated if necessary, before they move in or out. Surveillance and fly trapping are being expanded. Texas animal health officials will adjust their existing zone after the elk find, and USDA and Texas Parks and Wildlife are widening wildlife surveillance.
The Otero County cow is New Mexico's fifth case since the pest returned this summer, after a dog in Lea County and two horses and a calf in Grant County, the Santa Fe New Mexican reported. USDA has confirmed more than 50 cases across New Mexico and Texas since June. State agriculture secretary Jeff Witte said cooler weather slows the fly but does not remove the risk.
What owners should do
New Mexico officials are asking owners to report wounds that do not heal to the state Livestock Board and not to move affected animals. Ranchers and pet owners in neighboring states, including southern Colorado, should check animals for wounds through the fall, when officials say surveillance will continue into spring.
Sources
- CP24 (Reuters), “New World screwworm cases confirmed in wildlife in Texas, beef cow in New Mexico,” October 21, 2026
- Santa Fe New Mexican, “New World screwworm detected in Otero County cow,” October 21, 2026
Written by Action Global News from the sources above; quotations are attributed to the outlet that published them. See our editorial standards and corrections policy.
Frequently asked
Can screwworm infect pets?
Yes. One of New Mexico's five cases this year was a dog in Lea County. The larvae infest open wounds in warm-blooded animals.
Why does screwworm affect beef prices?
The U.S. halted livestock imports from Mexico for more than a year because of the pest, which contributed to record beef prices before a phased reopening began in August.