U.S. plans to combat spread of "man-eater" screwworms with $8.5M facility of flies in Texas

CBS News

19-06-2025

The U.S. government on Wednesday released a five-prong policy initiative to stop the spread of New World screwworms in live cattle and other animal imports, including its plan to build an $8.5 million insect dispersal facility in Texas.
Agriculture Secretary Brooke Rollins said her department plans to open what amounts to a fly factory by the end of the year. The facility will breed millions of sterile New World screwworm (NWS) flies at Moore Air Base, according to the initiative. The male flies will then be released into the wild to mate with females and prevent them from laying eggs in wounds that become flesh-eating larvae.
It would be only the second facility for breeding such flies in the Western Hemisphere, joining one in Panama that had largely kept the flies from migrating further north until last year.
An adult New World screwworm fly (left) and a New World screwworm larvae (right).
Denise Bonilla/USDA Agricultural Research Service via AP
"The United States has defeated NWS before, and we will do it again," Rollins said during a news conference at the South Texas air base with other state and cattle industry officials.
Late last year, the Texas Parks and Wildlife Department warned outdoor enthusiasts to watch out for animals that may be impacted by the dangerous "man-eater" parasites from flies that lay eggs in open wounds, nostrils, eyes and mouths. Last month, the U.S. Department of Agriculture suspended imports of live cattle, horses and bison from Mexico.
The New World Screwworm has been making its way further north through the Americas, Texas officials said, and the fly's appearance in southern Mexico has worried agriculture and cattle industry officials and veterinarians' groups.
According to the USDA, the New World Screwworm "is a devastating pest." The scientific name for the parasite, Cochliomyia hominivorax, is roughly translated to "man-eater," according to the USDA's Animal and Plant Health Inspection Service.
"When NWS fly larvae (maggots) burrow into the flesh of a living animal, they cause serious, often deadly damage to the animal," the USDA says. "NWS can infest livestock, pets, wildlife, occasionally birds and, in rare cases, people."
The USDA also plans to spend $21 million to convert a facility for breeding fruit flies near Mexico's southernmost border with Guatemala into one for breeding sterile New World screwworm flies, but it won't be ready for 18 months.
The U.S. bred and released sterile New World screwworm flies into the wild decades ago, and it was largely banished from the country in the 1960s. Previously, it had been an annual scourge for cattle ranchers and dairy farmers, particularly in the Southeast.
Mexican Agriculture Secretary Julio Berdegué said Wednesday in a post on X that Rollins' plan "seems to us a positive step in different aspects, it will strengthen the joint Mexico-U.S. work."
"We trust the enthusiasm for cooperation that Secretary Rollins mentioned, and based on objective results and the reports from the USDA mission visiting us this week, we will be able to restart exports of our cattle as soon as possible," he said.
The new Texas facility would be built at Moore Air Base, less than 20 miles from the Mexico border, and the USDA said it would also consider building a companion fly-breeding center there so that up to 300 million flies could be produced a week. The Panama facility breeds about 100 million a week, and the one in Mexico could breed as many as 100 million, as well.
The USDA has said the flies have been detected as close as 700 miles from the U.S. border, and some U.S. agriculture and cattle industry officials have worried that if the migration isn't checked, the flies could reach the border by the end of summer. Pressure from the U.S. prompted Mexico to step up efforts to control the fly's spread.
Buck Wehrbein, a Nebraska cattle rancher and the president of the National Beef Cattlemen's Association, said Moore Air Base had a fly-breeding facility in the 1960s that helped eradicate it in the U.S.
While there are treatments for New World screwworm infestations, cattle industry officials still worry that farmers and ranchers could see huge economic losses. They, agriculture officials and scientists also said the larvae can infest any mammal, including household pets, and it has occasionally been seen in humans.
"The only way to protect the American cattle herd from the devastating threat of New World screwworm is by having a sufficient supply of sterile flies to push this pest away from our border," Wehrbein said.
Texas officials said they are grateful the U.S. is taking the screwworm threat seriously and are pleased with the plans for combating it, including the new facility in Texas.
Officials in other states are watching the fly's migration, as well, and see that having sterile male flies outnumber the non-sterile ones is crucial to checking its migration.
"We have a real concern about wildlife because of their ability to cross the border unchecked somewhat, whether it's feral pigs, deer, wild cattle, whatever the case may be," Kansas Animal Health Commissioner Justin Smith said in a recent interview. "There's an opportunity for them to be our exposure risk."