New World screwworm reaches US wildlife as new cattle case widens the host picture

The United States has confirmed its first New World screwworm (NWS) infestation in wildlife, in an elk from Pecos County, Texas. On the same day, authorities in New Mexico confirmed a new infestation in a beef cow in Otero County. Together, the detections illustrate a widening epidemiological picture in which the parasite is now being found in livestock, companion animals and wildlife.

The elk, located on a game ranch, was reported after being harvested by a hunter. USDA has expanded wildlife surveillance, while Texas authorities are modifying an existing infested zone. The detection makes hunters and wildlife professionals increasingly important components of NWS surveillance.

A new cattle case in New Mexico

Separately, New Mexico animal-health officials confirmed NWS in a beef cow in Otero County. Authorities established a minimum 20-km (12.4-mile) infested zone around the affected location. Animals within the zone must be inspected and, when necessary, treated before movement. Surveillance and fly trapping are also being expanded to determine whether additional infestations are present.

The case is significant because cattle were also involved in the first US detection of the current episode: on June 3, NWS larvae were confirmed in the umbilical area of a three-week-old calf in Zavala County, Texas.

Cattle, goats, dogs... and now wildlife

Since June, confirmed US detections have demonstrated the broad host range characteristic of Cochliomyia hominivorax.

Cattle have accounted for several detections, beginning with young calves in Texas and now including the Otero County beef cow. Goats have also been infected, including a confirmed case in Gillespie County, Texas. Dogs are susceptible as well. USDA confirmed a case in a dog residing in Lea County, New Mexico, during June.

The Pecos County elk now adds a wild cervid to that list and represents the first confirmed US wildlife infestation of the current outbreak.

This range is biologically unsurprising: NWS larvae can infest wounds in virtually any warm-blooded animal. USDA considers livestock, pets and wildlife susceptible, with human infection occurring more rarely.

Wildlife could complicate eradication

The wildlife detection is particularly important because infestations in free-ranging animals are much harder to identify and treat. Since July 2025, USDA Wildlife Services had already examined 11,813 feral swine for NWS. The United States has an estimated six million feral pigs, including about 2.9 million in Texas, making them an obvious surveillance target despite no confirmed feral-swine case reported in these sources.

The central question is now whether the elk represents an isolated wildlife spillover or the beginning of sustained circulation in free-ranging hosts. That distinction will determine how difficult US eradication becomes: livestock cases can be found, treated and surrounded by movement controls; an expanding wildlife reservoir is considerably harder to contain.