Flesh-Eating Screwworm Parasite Found in US Wildlife for the First Time

Federal agriculture officials confirmed this week that New World screwworm, a flesh-eating fly larva that had been limited to livestock and pets since reappearing in Texas this year, has now turned up in a wild animal for the first time. The U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) said the case involved an elk on a game ranch in Pecos County, in far West Texas, discovered after a hunter harvested the animal.

"Early reporting is one of the most important tools we have" in containing the parasite, APHIS said in its announcement, urging hunters and landowners to watch for visible maggots, foul-smelling open wounds or animals showing unusual weakness, and to report suspected cases immediately.

An outbreak that started in cattle

New World screwworm — whose larvae burrow into living tissue rather than feeding on dead flesh, as most maggots do — was eradicated from the United States decades ago through a sustained sterile-fly release program but has pushed back north from Central America in recent years. The first confirmed U.S. case of the current outbreak was in a three-week-old calf in Zavala County in June, and case counts climbed through the summer, prompting Texas officials to establish a series of rolling quarantine zones across more than a dozen counties.

In response to the wildlife detection, the Texas Division of Emergency Management said the Texas Animal Health Commission is modifying the boundaries of a previously established infested zone to account for the elk's location, while USDA and the Texas Parks and Wildlife Department are expanding surveillance — including fly trapping — in the surrounding area.

Why a wildlife case matters more

Screwworm's spread into deer, elk and other free-ranging animals worries agriculture officials because wild herds move across property lines and quarantine boundaries that are far easier to enforce on fenced livestock. USDA has built out a dedicated public information hub at Screwworm.gov, including a wildlife-specific guidance page developed with hunting and outdoors groups, reflecting the agency's view that hunters are now a frontline surveillance network alongside ranchers and veterinarians.

The parasite does not spread through meat and poses no direct food-safety risk, APHIS has said, but untreated infestations can kill affected animals and depress local herd numbers. No additional wildlife cases had been confirmed as of Wednesday evening, and officials emphasized the overall case count, concentrated almost entirely in livestock, remains in the dozens rather than the hundreds.