Flesh-Eating Parasite Confirmed in South Texas Calf; USDA Establishes Quarantine Zone

Flesh-Eating Parasite Confirmed in South Texas Calf; USDA Establishes Quarantine Zone

We have been covering the battle to control the New World Screwworm (Cochliomyia hominivorax), a flesh-eating parasitic fly whose larvae infest open wounds of warm-blooded animals, including livestock, wildlife, pets, and occasionally humans, causing severe tissue damage and often death if left untreated. The pest appears to be infesting Mexico and heading north.

The U.S. Department of Agriculture (USDA) is using high-tech, sterile flies to contain and control these pests before they enter this country. A new federal facility is being built in South Texas to mass‑produce sterile New World screwworm flies as a biological control measure.

Hopefully, that facility will be up and running as soon as possible. New World screwworm has just been confirmed in at least one calf in South Texas, marking the first detection in the U.S. since the 1960s.

The USDA said the only animal affected was a 3-week-old calf in Zavala County, Texas, after larvae were identified in its umbilical area.

The USDA said it’s taking immediate action to eradicate the parasitic fly by establishing a 12-mile “infested zone” around the detection site and implementing quarantines, increasing traps for screwworms along the border and establishing an Incident Command Team with the Texas Animal Health Commission.

“USDA invested heavily in the tools needed to eliminate NWS ever since cases started increasing in Central America and Mexico. The United States has defeated this pest before, and we will do it again,” said Dudley Hoskins, under secretary for marketing and regulatory programs at USDA.

A screwworm was detected last week in Mexico, just 25 miles from the United States border, the USDA previously said. That encounter had been the closest to U.S. soil since at least last September, according to federal data.

A calf in southern Texas tested positive for the New World screwworm, the first instance of the deadly fly-borne parasite detected in U.S. livestock since 1966. https://t.co/DGqls32KmZ

— The Wall Street Journal (@WSJ) June 4, 2026

The USDA is working closely with local officials to address this situation as the sterile worm facility is slated to open next year.

“Although we’d hoped this day would never come, I trust @SecRollins and her team at @USDA to manage and prevent the spread of the New World screwworm,” outgoing Texas Sen. John Cornyn (R) wrote on social media. “My staff and I have been in touch with Zavala County and agriculture leaders and will remain in contact as we work together to fight this parasite and support Texas ranchers.”

In testimony to the House Committee on Agriculture on Thursday morning, Rollins pointed to a new sterile fly production facility being built in the U.S., which is expected to open next year.

In the meantime, the secretary cited ongoing joint intervention efforts between federal and state partners to combat the spread of this parasite.

“We are on it,” she told the committee. “We have invested almost a billion dollars since we came in the door last year to make sure that this doesn’t happen again.”

The efforts to control the infestation include a quarantine zone around the location where it was first detected.

It has also established a roughly 12-mile quarantine zone around the site and restricted the movement of warm-blooded animals, including livestock and pets, to further strengthen the response.

State veterinarians are urging ranchers and pet owners inside the quarantine zone to follow movement restrictions while eradication efforts continue.

Rollins said the USDA is confident enough in its preparations that it believes “there is no threat of mass infestation.”

USDA CONFIRMS FIRST NEW WORLD SCREW WORM DETECTION IN U.S. IN DECADES

Larvae were found in a 3-week-old calf in Zavala County, Texas. Officials have activated a quarantine zone and sterile insect releases to contain the spread.https://t.co/aB94NGgOLB pic.twitter.com/0bGiFEF7AO

— The Dallas Express News (@DallasExpress) June 4, 2026

The pest’s re‑emergence in Texas poses both animal‑health and economic risks and has the potential to further escalate already-rising beef prices.

The USDA estimated a screwworm outbreak would cost the Texas economy $1.8 billion in livestock deaths, labor costs and medication expenses. After decades of eradication, most cattle ranchers no longer have the experience or tools to diagnose and treat screwworm. Infestations can be cured, but treatment involves removing hundreds of larvae and thoroughly disinfecting wounds, a time-consuming, pricey and labor-intensive process.

“This is a pest we don’t want back. This is a bad thing,” said David Anderson, livestock economist at Texas A&M University.

America has defeated this pest before, armed with little more than ingenuity, sterile flies, and sheer determination, and the tools available today far surpass anything we had in the 1960s.

However, the first confirmed U.S. detection in decades is sobering, and the potential $1.8 billion economic wallop on Texas is not something to be brushed aside.

But between the 12-mile quarantine zone already in place, a new sterile fly production facility coming online next year, and a coordinated federal-state response effort from an engaged administration, the response to this infestation should go a long way toward being swift and successful.

Donations tax deductible
to the full extent allowed by law.