Federal officials confirmed two additional New World screwworm cases, including one in New Mexico, as authorities work to contain a flesh-eating parasite that threatens livestock, pets, wildlife and occasionally humans.
By yourNEWS Media Newsroom
Two more New World screwworm cases have been confirmed, including one outside Texas, raising concerns about the challenge of containing a flesh-eating parasite that could pose a major threat to the U.S. cattle industry.
The U.S. Department of Agriculture announced Monday that the latest confirmed cases bring the total to four, according to the Associated Press. Three cases involve calves in Texas, while the fourth involves a dog from Lea County, New Mexico.
The New Mexico dog was initially reported by the USDA as a Texas case, but officials later reclassified it after determining the animal lives in New Mexico. The dog’s travel history remains under investigation.
The New World screwworm is the larva of a fly that feeds on living flesh rather than dead tissue. Female flies lay eggs in open wounds on warm-blooded animals, including cattle, wildlife and pets. Humans can also occasionally become infested.
For decades, a government program kept the parasite contained at the southern end of Panama by breeding sterile male flies and releasing them from aircraft. When sterile males mate with wild females, the females do not produce offspring, helping stop outbreaks over time because female screwworm flies mate only once.
The first two cases in the current U.S. outbreak were found last week in calves located a few miles apart in south Texas. A third Texas case was announced Monday in La Salle County, southwest of San Antonio.
Scientists expect more isolated detections could appear as ranchers, veterinarians and officials increase surveillance, but they cautioned that new cases do not necessarily prove the parasite is spreading quickly.
“When that first case is seen, everyone is being vigilant and their eyes are on it more intensely,” said Edward Burgess, a University of Florida entomologist who studies the fly. “And when you are looking for something, you are more likely to see it.”
The USDA and cattle industry have been working to prevent a wider infestation since screwworm was detected in Mexico late in 2024. The pest, once a warm-weather scourge for U.S. ranchers, was eliminated from the United States in the 1960s.
So far, the parasite’s return has not had a major effect on beef prices, which already remain near record levels because of reduced U.S. cattle numbers. Although screwworm attacks live animals, it does not infest meat or fruit. Livestock can also be treated with a dozen government-approved medications.
Canada temporarily halted imports of cattle, horses and other livestock from Texas on Friday. The parasites favor humid environments with temperatures of at least 77 degrees Fahrenheit, or 25 degrees Celsius, making them more likely to be a summer concern farther north.
USDA Secretary Brooke Rollins was scheduled to hold a Monday afternoon news conference on the infestation after a briefing at the U.S. Livestock Insects Research Laboratory in Kerrville, Texas.
Burgess said the long-term solution remains the sterile fly program, but expanding that response will take months. The USDA is working to increase sterile fly production at facilities outside the United States and build a large fly production plant in Texas.
Texas Agriculture Commissioner Sid Miller has criticized the federal timeline, warning that a slower response could endanger the cattle industry. Miller has argued that poison bait could eliminate the problem within a few months.
The USDA and other experts have said the bait has not been proven to work and could harm other flies, animals and humans.
“What the hell is a good fly?” Miller said in an interview Monday.
The confirmed cases in Texas and New Mexico show the difficulty of stopping a parasite that can move through livestock, pets and wildlife. Federal and state officials are now racing to prevent the handful of detections from becoming a wider infestation that could damage ranchers and further strain the cattle industry.
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