ByREUTERS

JUNE 4, 2026 07:13

Updated: JUNE 4, 2026 07:28

The New World screwworm, a parasitic fly known for consuming living tissue of warm-blooded hosts, has appeared in a Texas calf according to the US Department of Agriculture announcement late Wednesday, introducing a major risk to domestic livestock.

Officials verified the infestation in a young animal near La Pryor, Texas, located approximately 30 miles (48 km) northeast of the border with Mexico, delivering unwelcome news to ranchers who anticipated such an event as the pest moved northward across Mexico in recent months.

USDA Secretary Brooke Rollins confirmed this as the sole known case in the United States and the first occurrence in Texas since 1966.

Such an incursion may further reduce already diminished cattle numbers, now at their lowest point in 75 years, which has already curtailed beef output and pushed consumer prices to unprecedented levels.

The discovery endangers Texas livestock operations, potentially resulting in losses reaching 1.8 billion dollars should the parasite proliferate, while undermining years of costly federal prevention measures, according to specialists.

Texas Agriculture Commissioner Sid Miller faulted the USDA for permitting the screwworm to enter the country.

Texas livestock industry threatened

"The agency failed to deploy all possible resources promptly and depended on an incomplete approach requiring years for completion," he stated. Rollins emphasized that sterile fly releases represent the primary defense and noted substantial USDA investments in this method.

Earlier Wednesday, Reuters indicated that tissue samples from a suspected case at the La Pryor ranch had been forwarded to the federal laboratory in Ames, Iowa. Feeder cattle futures on the Chicago Mercantile Exchange declined further, closing 1.7 percent lower amid concerns that a domestic confirmation could weaken beef demand.

These parasitic flies deposit eggs in wounds or mucous membranes of warm-blooded creatures. Upon hatching, the larvae consume flesh with specialized mouthparts, often proving fatal without intervention, and primarily spread via transport of affected animals.

While capable of infecting humans and pets, experts assess the danger to people as minimal with human incidents uncommon. The parasite presents no concerns for food safety.

The USDA implemented movement restrictions for animals within a 20 km (12.4 mile) radius of the detection site, dispersed sterile flies locally, expanded wildlife monitoring, and dispatched a response unit. Rollins added that a plane carrying treatment supplies was en route to South Texas.

"Safeguarding the livestock sector constitutes a critical national security priority," remarked Dudley Hoskins, a USDA under-secretary.

Impact on cattle supply, beef prices

A widespread outbreak would impose severe financial strain on Texas ranchers, the leading cattle-producing state, through animal mortality, added labor, and treatment expenditures.

The US has maintained closure of its Mexican border to live cattle imports for over a year to block the parasite, allocating millions to curb its progress in Mexico, enhance sterile fly output, broaden trapping programs, and heighten surveillance.

Mexico has recorded 27,449 screwworm cases since November 2024, including 2,094 active ones, while boosting inspections and preparing a US-supported sterile fly facility in its southern region for operation by late June.

Previously, the US imported over one million Mexican cattle annually for feedlot finishing and beef processing.

Although treatable, infestations demand extraction of numerous larvae followed by complete wound disinfection, an expensive and labor-heavy procedure.

The pest has advanced northward from Central America through Mexico and remains established in parts of the Caribbean and South America. In August, the US reported its initial travel-related human case connected to the current outbreak in a traveler returning from El Salvador.

The previous incursion affecting US border states during the 1960s severely impacted local wildlife and inflicted millions in rancher damages.

The United States eliminated screwworms in the 1960s via large-scale releases of sterilized male flies that produce infertile offspring when mating with wild females.

A Texas facility for sterile fly production is projected to begin operations no earlier than late 2027.

On Wednesday, the leading August feeder cattle contract dropped 5.80 cents to close at 342.625 cents per pound. August live cattle futures declined 1.8 cents to 237.85 cents per pound. Shares in major processors Tyson Foods and JBS also decreased.