First case of flesh-eating screwworm in 60 years confirmed in U.S.
June 4 (UPI) -- Agriculture Secretary Brooke Rollins confirmed the first case of a flesh-eating screwworm fly in the United States in 60 years.
Rollins posted on social media Wednesday that the Cochliomyia hominivorax, also known as the New World screwworm fly, has been discovered in Zavala County, Texas. Its presence threatens an already weak cattle herd in the United States.
The case was discovered in a 3-week-old calf in La Pryor, Texas.
Currently cattle numbers in the United States are at their lowest in 75 years.
The screwworm fly lays eggs in open wounds and body openings, the U.S. Centers for Disease Control and Prevention says. After its eggs hatch, they turn into maggots, burrow into their host's body and feed on their flesh.
These parasites can enter the body through the eyes, ears, nose, mouth or genitals of warm-blooded mammals.
A female screwworm can lay up to 300 eggs at a time and 3,000 eggs during their 10- to 30-day lifespan.
"It can cause serious, often deadly damage to animals and people in areas where the pest spreads," the U.S. Department of Agriculture said in a statement. "While NWS is present in parts of South America -- where infections in animals and people continue to occur -- it was eradicated from the United States decades ago. In recent years, NWS has moved northward through Central America and Mexico."
Texas Agriculture Commissioner Sid Miller has called on the federal government to assist in containing the spread of the parasite before it "becomes a full-blown agricultural disaster."
In past efforts to combat the spread of the parasite, the USDA has released sterile flies into the area where it is present. Female flies typically only mate once and if they mate with a sterile male fly they will be unable to produce offspring.
The USDA said it has begun releasing sterile male flies in the region where the screwworm was detected. It has also established a quarantine zone spreading across about 12 miles.
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This story was originally published June 4, 2026 at 10:57 AM.