Why a Texas elk is raising alarms over a flesh-eating parasite

An elk harvested by a hunter on a Pecos County game ranch has become the first U.S. wildlife case of New World screwworm.

The USDA confirmed the detection on Oct. 21 after the elk was reported from the West Texas ranch. New World screwworm is a parasitic fly that lays eggs in open wounds or body openings of warm-blooded animals. Its larvae then feed on living tissue. It can rarely affect humans, but it is primarily a threat to livestock and wildlife.

What happens next: The USDA and Texas Parks and Wildlife Department are conducting additional wildlife surveillance in the area. The Texas Animal Health Commission will also modify an infested zone that had already been established before the elk case.

Texas wildlife officials are asking hunters and landowners to keep an eye out for visible maggots in wounds, foul-smelling injuries, open or enlarging wounds, and animals that appear weak or distressed. Infestations can also occur around an animal's nose, mouth, ears, eyes or genital areas. Suspected cases should be reported immediately.

Why it matters: The parasite had been eradicated from the United States decades ago, but has spread north through Central America and Mexico in recent years. The USDA confirmed a Texas case in a calf in June, a livestock detection in the state. The elk case is the first time it has been found in U.S. wildlife.

New World screwworm does not affect food safety, according to the USDA, but it can harm meat production. The United States halted livestock imports from Mexico last year over screwworm concerns, then resumed some trade in August through an Arizona port under a phased reopening plan.

The larger concern: Wildlife can move through areas where ranchers are trying to contain the parasite, which makes finding and reporting cases quickly more important. The open question for the USDA's next surveillance round is whether this was an isolated elk or a foothold in West Texas.