September 26, 2025

Screwworm ‘dangerously close’ to US, Texas officials warn

Texas officials are urging residents to check their pets and livestock, as well as use pesticide bait, after a confirmed infection of flesh-eating New World Screwworm (NWS) in an 8-month-old cow less than 70 miles from the United States border in Mexico. That’s the closest a confirmed case has been to the U.S. border this year. 

Where was the case confirmed?

According to the U.S. Department of Agriculture, the infected cow had recently been transported to a region in southern Mexico where NWS cases are active. The feedlot where the animal was is near a major highway leading to Laredo, Texas. Officials describe the highway as “one of the most heavily trafficked commercial thoroughfares in the world.”

Texas officials call for major response

Texas Agriculture Commissioner Sid Miller said Tuesday in a news release that he is requesting a significant response to the discovery. 

“The screwworm is dangerously close,” Miller said in a statement. “It nearly wiped out our cattle industry before — we need to act forcefully now. That’s why I insist we start using pesticide bait immediately.”

Warning to pet and livestock owners

Texas officials also called on residents of southern Texas to examine their pets and livestock for signs of screwworm larvae, including oozing or large wounds, as well as behavioral changes in animals. Officials say that the maggots and eggs can often be found around the nose, ears and genitals or the navel of newborn animals.

NWS infections in humans are rare but can be serious.

“The recent case found only 70 miles south of our border should trigger serious concern,” Miller said. “Although it hasn’t crossed into our territory yet, its proximity means we must get ready for its potential arrival.”

The confirmed parasitic infection comes after Mexican officials found another case around 370 miles from the U.S. border in Mexico this summer.

The parasite is of significant concern for the agriculture industry and veterinarians, who note the larvae from screwworm flies can prove deadly for animals if left untreated. 

Proactive measures

The Texas Department of Agriculture announced in July it would deploy a bait to mimic the odor of an open wound in order to lure adult screwworm flies. A similar method was used to help kill off the flies during an isolated outbreak in the 1970s after the parasite’s initial eradication from the U.S. in the 1960s.

The U.S. Department of Agriculture also said earlier this year that air drops of sterile male flies were slated to begin this summer in an effort to proactively eradicate the parasite.

Concerns over the screwworms’ potential impact on livestock sent the price of beef soaring in May ahead of Labor Day, as Straight Arrow News previously reported.

The U.S. paused imports of cattle and other livestock from Mexico as a preventative measure against the parasite as well. According to Ars Technica, officials set up around 8,000 traps in southern border states like Texas, Arizona and New Mexico, but have not found evidence of the screwworm in the U.S. to date.

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