New World screwworm has been detected in an elk in Texas, marking the first confirmed case of the flesh-eating parasite in U.S. wildlife during the current outbreak.
The U.S. Department of Agriculture (USDA) confirmed New World screwworm, or NWS, in an elk in Pecos County, Texas, on October 21. The elk, which was confirmed female by the Texas Parks and Wildlife Department (TPWD), was shot by a hunter on a game ranch. The animal was then reported to authorities.
A sample was collected from it and identified as New World screwworm at the USDA Agricultural Research Service's Knipling-Bushland U.S. Livestock Insects Research Laboratory in Kerrville.
The discovery comes after a series of cases have risen in domestic animals in the U.S. this year. The first animal case in the current outbreak was confirmed in a three-week-old calf in Zavala County, Texas, on June 3 by the USDA.
Where Has New World Screwworm Been Found?
The USDA has a live dashboard recording confirmed U.S. detections, including individual animal cases by state, county, species, confirmation date, and status, as well as traps where at least one wild New World screwworm fly has been detected.
Confirmed U.S. cases are currently in just two states: Texas and New Mexico. The outbreak began in Texas in June and has subsequently travelled rapidly across a number of counties. Early Texas cases included animals in Zavala, La Salle, Gillespie, Edwards, Tom Green and Sutton counties.
Later official orders published by the Texas Animal Health Commission (TAHC) reported detections including a goat in Terrell County on June 22, a sheep in Pecos County on July 14, a type of cattle in Starr County on July 18, another bovine in Brewster County on July 9, and also a dog there on October 2, and, more recently, another cattle case was detected in Pecos County on October 10.
New Mexico's official New World screwworm website currently reports three confirmed cases. Two, confirmed on October 16, are in Grant County, were found in a calf and a horse, while the other is in Otero, confirmed on October 21, and involves a cow.
The Texas situation is wider than the locations of individual cases.
The TAHC currently has NWS-related animal movement restrictions in place across parts of 12 Texas counties: Brewster, Crockett, Edwards, Jeff Davis, Pecos, Presidio, Schleicher, Starr, Sutton, Terrell, Val Verde and Zapata.
What Is New World Screwworm?
New World screwworm (NWS), Cochliomyia hominivorax, is a parasitic fly that lays its eggs on the living tissue of warm-blooded animals, usually in open wounds, genitalia, or moist body openings like nostrils, eyes, or mouths.
Once the eggs hatch, the larvae, or maggots, burrow (or screw, hence the name) deeper into living flesh using sharp hooks in their mouths. This makes them different from many other fly larvae, because they feed primarily on dead or decaying tissue.
The resulting condition can cause severe wounds, infection, and pain and can even kill an animal if it’s not treated. Animals with infections can show signs including visible maggots, enlarging wounds, a foul smell, loss of appetite, head shaking, weakness, or unusual isolation.
Because NWS can affect livestock, pets, and wildlife, its spread poses a serious concern for animal health and the agricultural industry.
What Does It Mean for Humans?
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Humans can also become infected, although U.S. health officials say the risk remains very low. So far, there have been no reported human cases of NWS contracted within the United States during the current outbreak, according to the Centers for Disease Control (CDC).
One infection was confirmed in the U.S. in August 2025 in a person who had returned after traveling to El Salvador, meaning it was travel-associated rather than acquired domestically.
Similar to animals, human infestation can happen when the flies lay eggs in a wound or body opening. Symptoms can include painful wounds that refuse to heal, bleeding or a foul-smelling discharge, and the appearance or sensation of maggots moving within a wound. The CDC advises people who see or feel larvae in a wound to seek medical care immediately.
But questions have been raised about the impact NWS may have on food sources, particularly beef.
The USDA has stressed that New World screwworm is not considered a food-safety threat, confirming that “any affected animal would be identified during USDA Food Safety and Inspection Service inspection, and no contaminated product would enter commerce.”
Following the detection of NWS in the elk, the USDA and TPWD are carrying out additional wildlife surveillance around the affected area. Officials are urging hunters in particular to inspect animals for wounds and larvae and report any suspicious findings immediately.
Newsweek has contacted the TPWD, USDA, and TAHC for comment.
Newsweek’s reporters and editors used Martyn, our AI assistant, to produce this story. Learn more about Martyn here.
Contact Newsweek editor on this story: Edward Pearcey.