Parasitic larvae from flies known as New World screwworm are infesting cattle in Mexico, and officials are racing to slow the spread across the southern border before the infestation overtakes American livestock, damages several agricultural industries and spikes the cost of beef.
The outbreak has alarmed the U.S. Department of Agriculture (USDA), which shut down all imports of live cattle, horses and bison across the southern border in November 2024, temporarily lifted the ban and then reimposed it in May. Though a lab in South America is working to eradicate the pest, experts in the industry that spoke with the Daily Caller News Foundation are concerned that an outbreak could hit American beef production hard and leave consumers paying higher prices if the situation is not controlled.
“This is a significant concern in our industry,” Colin Woodall, chief executive officer of the National Cattlemen’s Beef Association, told the DCNF. “This pest is a flesh-eating parasite, and we need to make sure that we can protect ourselves and ultimately eradicate it once it gets to the United States … This could be a fight that takes us a while to ultimately win.”
Given that the U.S. imports over a million cattle from Mexico on average annually, a prolonged import freeze will culminate in climbing beef costs as the supply of cattle is restricted, experts in the industry told the DCNF.
The freeze has left millions of dollars’ worth of cattle stranded in pens in Mexico, sparked alarm among ranchers over risks to their livelihoods and prompted state authorities to caution about potential supply chain disruptions and rising beef prices, as reported in January by 25 News KXXV, a local central Texas news outlet.
Cattle can get infected by the flesh-eating larvae through a recent brand, a healing ear tag or even a wound as small as a tick bite, though screwworm infestations are “not a cattle specific issue,” Woodall said. Any warm-blooded mammal, including livestock, wildlife, pets and even humans — in rare cases — get infested with the flesh-eating larvae after infected flies lay their eggs in any open wound as small as a scrape.
“It can be extremely gruesome to see not only cattle, but deer and dogs and other animals… the pain and the suffering that the animal has to go through is what makes this just so incredibly terrible from an animal health perspective,” Woodall said.
Estimates predict that if the fly migrates to the U.S., Texas could face billions in economic losses, including conservative estimates of $2.1 billion in the cattle sector and $9 billion in the hunting and wildlife sectors, according to a Texas A&M AgriLife analysis. Texas produces more beef than any other state in the U.S.
“Our ultimate goal remains keeping it entirely out of the United States, but we know that we must be fully prepared should it come further north,” a USDA spokesperson told the DCNF.
The economic impact on the industry stems from increased labor and production costs, along with the expenses for medications required to treat affected cattle, Woodall explained.
Other industry experts told the DCNF that the economic damage in the case of a prolonged import freeze and a screwworm outbreak in the U.S. would be serious.
“It’s a devastating deal,” Mike Shultz, vice-president of the Organization for Competitive Markets and founder of the Kansas Cattlemen’s Association told the DCNF. “We’ve been concerned … I think we need to take all measures necessary to secure our food supply, and that starts at the border.”
“All security issues start at the border. It doesn’t matter what you’re talking about. If you don’t have a secure border, you have nothing,” Shultz continued.
“It’s really been a major concern,” President of U.S. Commodities Don Roose told the DCNF. Roose mentioned that one mad cow disease case in 2003 led to the cattle market tanking for a week, and that a recent rumor regarding a screwworm outbreak also shook the market for a few days.
“Mother Nature gave us a favor,” Woodall said, noting that the pest is eradicated through unleashing sterile flies where screwworms are active that will cause them to die out as they go through their lifecycle.
Perhaps the most pressing question is currently how many sterile flies would be needed to “slow the march down and ultimately push it all the way back into South America,” Woodall continued.
The Panama-U.S. Commission for the Eradication and Prevention of the Cattle Borer Worm (COPEG) lab in Panama is making millions of sterile flies a week, though Woodall is worried it will not be enough. The USDA pledged to invest $21 million into renovating a production facility in Mexico.
It’s a rush to approve and construct a domestic, sterile New World screwworm production facility, according to Woodall.
“We know that our efforts will likely require more sterile flies than the facilities in Panama, and eventually, Mexico, can produce,” the USDA spokesperson said, confirming that the agency is considering a domestic production facility.
A screwworm outbreak in the 1960’s was alleviated through the same method of unleashing sterile flies, though not before a multi-million-dollar loss hit the industry.
“It’s devastating,” Stephen Diebel, first vice president of Texas and Southwestern Cattle Raisers Association, told the DCNF. “It’s not an immediate panic … Luckily, we do have a solution for this.”
It is vital that the sterile flies are produced and unleashed in a timely manner so that the outbreak does not “escalate to the magnitude that we fear,” Diebel added.
“Effective eradication, which remains our goal, requires a three-pronged approach: robust, active field surveillance with education and outreach to ensure prevention, treatment, and early detection; controlled animal movement to limit spread; and sustained sterile insect dispersal,” a USDA spokesperson told the DCNF. “Mexico has been and will continue to be a key partner as we work to eradicate New World screwworm; we cannot do this alone.”
The embassy of Mexico and COPEG did not respond to the DCNF’s requests for comment.
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