The screwworm, a flesh-eating parasite and longtime foe of American ranchers, is back in U.S. cattle after decades.The U.S. Department of Agriculture confirmed at least three infected cattle in Texas this week. The beef industry has already been grappling with the smallest cattle herd in 75 years due to prolonged droughts.Those smaller herds have helped drive retail beef prices to a record $9.64 per pound in April, up 13% from the previous year, according to USDA data.With only a handful of cases so far, it’s too soon to tell if prices will jump more because of the parasite. Instead, experts say screwworm cases will likely keep existing prices elevated for grocery shoppers. “It just makes it a longer timeline before the cattle industry will really start to rebuild,” Tom Johnston, editor-in-chief of trade publication Meatingplace, told CNN.Grocery shoppers could get hit with higher prices if the screwworm cases turn into a full-blown outbreak. That could cost $3 billion across the Southwest, according to a report by the Federal Reserve Bank of Dallas.But the cattle industry isn’t there yet. And in the short term, consumers are unlikely to see a big change in beef prices.“This will be a burden on cattle producers, but it is one where there’s light at the end of the tunnel,” Todd Thrift, a beef sciences professor at the University of Florida, told CNN.Impact at the grocery storeEven if a possible outbreak pushes up prices, the changes would be incremental rather than a sudden jump like the price of eggs during the bird flu outbreak.Screwworm would increase labor and medicine costs for ranchers, David Anderson, an agriculture economist at Texas A&M University, told CNN.Though screwworm doesn’t spread from animal-to-animal like a virus, female adult flies lay eggs in fresh wounds of warm-blooded animals. Those larvae feed on the hosts and can cause bacterial infections or death.An outbreak would also pile stress onto an already difficult profession.“That has a significant not only financial burden but also just a mental toll on those cattle producers,” Colin Woodall, CEO of lobbying group the National Cattlemen’s Beef Association, said.An old enemy returnsThis isn’t the cattle industry’s first rodeo with the screwworm. The New World screwworm fly has been the bane of existence for U.S. cattle ranchers since at least the 1930s. In the 1950s, scientists figured out they could sterilize flies to overwhelm the local fertile fly population, preventing females from reproducing.Cattle producers in affected states lost up to $50 million to $100 million per year before full eradication in the ‘60s, according to a 2025 analysis from USDA.But cases have surged in Central America since 2023, and the fly has recently made its way up to Texas from Mexico. In May 2025, USDA Secretary Brooke Rollins announced the border would close to livestock imports from Mexico due to the rise of screwworm cases.But that border closure also contributed to higher beef costs in the past year, Anderson said. In Texas, feedlots where Mexican cows were fattened up were hit hard, and that also affected beef supply in the United States.A race against timeThe question is not whether the flies can be contained but how quickly.USDA broke ground on a facility to mass produce sterile screwworm flies in Texas in April, with production expected to start in November 2027. It also invested millions into modernizing a facility in Mexico, which is expected to reopen this summer. USDA has also been bringing in 100 million sterile flies per week from a facility in Panama.The department also said it sought approval from the U.S. Environmental Protection Agency to release NovoFly, a genetically modified male-only sterile fly that would double capacity.“It’s the technology that we used to win the battle in the 60s, and it will definitely help again,” Woodall said.CNN’s Jen Christensen contributed to this report.
The screwworm, a flesh-eating parasite and longtime foe of American ranchers, is back in U.S. cattle after decades.
The U.S. Department of Agriculture confirmed at least three infected cattle in Texas this week. The beef industry has already been grappling with the smallest cattle herd in 75 years due to prolonged droughts.
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Those smaller herds have helped drive retail beef prices to a record $9.64 per pound in April, up 13% from the previous year, according to USDA data.
With only a handful of cases so far, it’s too soon to tell if prices will jump more because of the parasite. Instead, experts say screwworm cases will likely keep existing prices elevated for grocery shoppers. “It just makes it a longer timeline before the cattle industry will really start to rebuild,” Tom Johnston, editor-in-chief of trade publication Meatingplace, told CNN.
Grocery shoppers could get hit with higher prices if the screwworm cases turn into a full-blown outbreak. That could cost $3 billion across the Southwest, according to a report by the Federal Reserve Bank of Dallas.
But the cattle industry isn’t there yet. And in the short term, consumers are unlikely to see a big change in beef prices.
“This will be a burden on cattle producers, but it is one where there’s light at the end of the tunnel,” Todd Thrift, a beef sciences professor at the University of Florida, told CNN.
Impact at the grocery store
Even if a possible outbreak pushes up prices, the changes would be incremental rather than a sudden jump like the price of eggs during the bird flu outbreak.
Screwworm would increase labor and medicine costs for ranchers, David Anderson, an agriculture economist at Texas A&M University, told CNN.
Though screwworm doesn’t spread from animal-to-animal like a virus, female adult flies lay eggs in fresh wounds of warm-blooded animals. Those larvae feed on the hosts and can cause bacterial infections or death.
An outbreak would also pile stress onto an already difficult profession.
“That has a significant not only financial burden but also just a mental toll on those cattle producers,” Colin Woodall, CEO of lobbying group the National Cattlemen’s Beef Association, said.
An old enemy returns
This isn’t the cattle industry’s first rodeo with the screwworm. The New World screwworm fly has been the bane of existence for U.S. cattle ranchers since at least the 1930s. In the 1950s, scientists figured out they could sterilize flies to overwhelm the local fertile fly population, preventing females from reproducing.
Cattle producers in affected states lost up to $50 million to $100 million per year before full eradication in the ‘60s, according to a 2025 analysis from USDA.
But cases have surged in Central America since 2023, and the fly has recently made its way up to Texas from Mexico. In May 2025, USDA Secretary Brooke Rollins announced the border would close to livestock imports from Mexico due to the rise of screwworm cases.
But that border closure also contributed to higher beef costs in the past year, Anderson said. In Texas, feedlots where Mexican cows were fattened up were hit hard, and that also affected beef supply in the United States.
A race against time
The question is not whether the flies can be contained but how quickly.
USDA broke ground on a facility to mass produce sterile screwworm flies in Texas in April, with production expected to start in November 2027. It also invested millions into modernizing a facility in Mexico, which is expected to reopen this summer. USDA has also been bringing in 100 million sterile flies per week from a facility in Panama.
The department also said it sought approval from the U.S. Environmental Protection Agency to release NovoFly, a genetically modified male-only sterile fly that would double capacity.
“It’s the technology that we used to win the battle in the 60s, and it will definitely help again,” Woodall said.
CNN’s Jen Christensen contributed to this report.
