5 Screwworm Infections Found in U.S.

An adult New World screwworm fly. (Denise Bonilla/U.S. Department of Agriculture via AP)

The Department of Agriculture confirmed an additional three cases of New World screwworm, bringing the total number of detections in the U.S. to five and raising concerns over a broader spread of the parasite.

The fly was detected in a calf in La Salle County, Texas, a goat in Gillespie County, Texas, and a dog in New Mexico, the agency said. That comes after two cases were confirmed last week in calves in Zavala County in South Texas, marking the first U.S. detection of the fly in over a decade, and the first in cattle in about five decades.

The detection in La Salle County is close to Zavala, where the past two cattle cases were confirmed. But the confirmation of screwworm in the dog places the pest far outside that region and across state lines. The animal had initially been linked to Andrews County in Texas because it was reported by a veterinarian in the state, but the dog’s home is in Lea County, N.M., the USDA clarified.

While that is “believed to be an isolated case,” the USDA and state partners are inspecting additional animals in the dog’s home and increasing outreach in the area “because the dog’s recent travel and exposure history remain unknown,” the agency said. The USDA said earlier that the dog was believed to be in Mexico recently. The agency is also gathering more details of the case involving the goat. 

Agriculture Secretary Brooke Rollins, speaking on CNBC on June 8, said the U.S. is “going to do everything we can, investing over $1 billion” to push the New World screwworm out of the country.

🚨 With the recent detection of New World screwworm in a 3-week-old bovine in Zavala County, TX, USDA urges residents to contact your veterinarian right away if you see any suspicious wounds, maggots, or infestations in your animals or herd.

If you see signs of maggot… pic.twitter.com/lxxsjIgDcb — Dept. of Agriculture (@USDA) June 4, 2026

RELATED: USDA Races to Impose Quarantine After Texas Screwworm Case

The spread risks more cautionary measures to limit cattle movement. Georgia’s Agriculture Department said June 5 that it would restrict the movement of both livestock and pets into the state from a dozen Texas counties, while Canada is blocking the transit of livestock that has been in Texas within a three-week window.

That adds more worries for a U.S. beef industry already struggling with supply tightness as the domestic herd has dwindled to a 75-year low. 

The detection of screwworm is probably going to further delay any efforts to expand the U.S. herd, said Glynn Tonsor, a professor of agricultural economics at Kansas State University. Tonsor said he was “pretty vocal” late last year that more ranchers would start the process of expansion this summer, but increased dryness — and now screwworm — are creating more uncertainty, he added.

Tighter cattle supplies, even if limited to Texas alone, would also continue to pressure beef processing plants that have already been operating at losses due to the cattle shortage. Companies including Tyson Foods and JBS NV have resorted to closing plants amid high cattle prices. 

Tyson ranks No. 9 on the Transport Topics Top 100 list of the largest private carriers in North America and No. 1 among agriculture/food processing carriers. JBS ranks No. 86 on the TT Private 100 and No. 12 on the agriculture/food list. 

Feeder cattle futures in Chicago are up about 2% since June 3, when the first Texas case was reported but not yet confirmed. Tyson shares were down as much as 2.3% on June 8, while JBS slumped as much as 6.1% to the lowest price since U.S. trading began a little over a year ago.

The screwworm is a fly whose larvae burrow into the flesh of animals, leading in some cases to death. Infestations are treatable, including through a spate of medications the U.S. Food and Drug Administration has already approved under emergency use, and the USDA has said the food supply is safe.

The 1976 outbreak in Texas affected over 1.5 billion head of cattle and was ultimately eradicated through the dispersal of sterile flies that limited the pest’s ability to reproduce. The USDA plans to release 8 million sterile flies each week to the current control zone, which spans 12 miles around the initial detection in La Pryor, in Zavala County.

The dispersal of such flies will need to reach 400 million a week, Rollins said on CNBC. A facility in Panama produces and disperses 100 million flies a week, “but we need a lot more than 100 million flies a week to eradicate,” she said.

A production facility under construction in Texas — the first of its kind in the U.S. — is expected to produce 100 million flies a week once it begins operating in November 2027, with further growth to full capacity of 300 million flies a week.

JUST NOW: @SecRollins in Kerrville, TX touring the cutting-edge @USDA_ARS Knipling-Bushland Livestock Insects Research Lab — the epicenter of game-changing research in our war on New World Screwworm.

This facility has developed a novel sterile fly strain that doubles production… pic.twitter.com/JTCsoDDGdt — New World Screwworm Rapid Response (@Screwworm_RR) June 8, 2026