In the latest flare-up, the Trump administration has blamed the Biden administration’s immigration policies for driving the insect northward through the Darien Gap, out of its traditional habitat in South America. Democrats say the Trump administration bears some blame for temporarily reversing a Biden-era Agriculture Department decision to close southern ports of entry to live cattle imports to prevent the spread of screwworm into the U.S. last year. The Department of Government Efficiency’s workforce cuts last year to the USDA’s Animal and Plant Health Inspection Service, as well as programs targeting the screwworm, left the country vulnerable to the latest outbreak, Democrats ranging from Sen. Raphael Warnock (D-GA) to Rep. Shri Thanedar (D-MI) argue.

The allegations have sparked pushback from Agriculture Secretary Brooke Rollins. She said this week that it was thanks to the Trump administration that officials were able to keep the screwworm at bay for as long as they did.

“There has been zero impact to this mission area, specifically to the screwworm, based on that reduction in force,” the agriculture secretary told reporters Monday. “Every model showed that the New World screwworm would be here in Texas by early last summer, so we bought ourselves an additional year to prepare for this moment.”

The Texas Animal Health Commission, the lead Texas agency on screwworm response, told the Washington Examiner that “lots of factors” spurred the outbreak.

“There are lots of things that we could try to point the finger at,” TAHC communications director Erin Robinson said. “I think the way that it got to Texas was animal movements, you know, we put animals on the back of trailers, and if they’re not, you know, if they’re infested, that is moving that farther north, and so if you see how this is tracked up through Mexico, you’ll see that, I mean, it is some natural fly movement, but it has jumped pretty fast, and so the movement of those animals certainly is a factor through that.”

The USDA and most Texas officials say a lack of sterile fly facilities forms the core problem in tackling the outbreak, and they have touted efforts to expand domestic production of such screwworm-fighting facilities in Texas. They have expressed confidence that response efforts, fueled by the groundbreaking “Novo Fly” method, new drugs sanctioned by the Food and Drug Administration, and state-coordinated information campaigns, are “going better than we could have imagined.”

“The partnerships that we have been working on for two years, the planning that we’ve done has come to fruition in such an incredible way,” Robinson said. This is a highly preventable and highly treatable condition.”

Dr. Justin Welsh, the technical services lead for the Merck Animal Health team that developed Exzolt Cattle-CA1, one of the newest screwworm prevention and treatment drugs, said he would “by no means” characterize the situation as a crisis.

“I think we’re going to be just fine,” he said. “There’s always going to be some that think that your governmental entities should be doing more … [but] we can apply products like Exzolt Cattle-CA1 on the cattle, and prevent, for a number of weeks, the infestation from happening. So, we’ve got a lot of good stuff that’s going to help us keep this thing pushed back.”

The New World screwworm spawns maggots that feed on live warm-blooded flesh, posing a threat to livestock, particularly in Texas, where a total of eight cases have now been declared. One additional case has been declared in neighboring New Mexico. Female flies typically lay up to dozens of eggs at a time in a wound or another entry point, such as the nose or ears. When the eggs hatch, the larvae burrow into the flesh, eating it alive.

The U.S. grappled with screwworms for years before officials in the 1950s started using an innovative solution known as the sterile fly technique, in which sterile males are released in the wild to mate with females. That means they cannot have offspring, essentially breeding the pest out of existence, as they have a life span of only a few weeks and females mate only once. The tactic led to the eradication of the pest in the U.S. in 1966, though outbreaks continued for years.

After decades of aggressive action, officials were able to push the fly southward, eradicating it from Mexico, then beyond Central America. Eventually, authorities established a final buffer zone in the 1990s at the Darien Gap, which connects Panama to Colombia, a measure that effectively prevented the New World screwworm from exiting South America into Central and North America. By 2006, officials had built a sterile fly production facility in Panama to further maintain the barrier zone.

Sterile fly production facilities in Florida, Texas, and Mexico further beefed up eradication efforts. But as the crisis faded and pests retreated into South America, the facilities began to close.

By the early 1970s, factories in Orlando, Bithlo, and Sebring, Florida, were shuttered, as the eradication campaign ended successfully in the Southeast and turned toward the Southwest. In the early 1980s, the USDA ended production of sterile flies at the former Moore Air Base in Mission, Texas, because “conditions were so positive.” In 2012, six years after the New World screwworm was declared eradicated in Panama, the Tuxtla Gutierrez facility in the southern Mexican state of Chiapas, which could produce 550 million sterile screwworm flies weekly, was shut down for economic reasons, leaving the Panama-based factory as the U.S.’s primary supplier.

“There was lots of fly production facilities across the nation, or across Mexico and Texas, and Central America, because we needed them,” Robinson said. “And then we got this fly pushed back to the Darien Gap, and … we no longer needed that many flies, and so … we could maintain it with the one facility in Panama. Now we’re at a point where we need more flies, and that facility in Panama is at max capacity.

Neal Wilkins, who leads an organization of Texas ranchers, warned last year that shutting down the factories was a mistake. 

“It was a big loss when the USDA gave the existing facility in Chiapas to the Mexican government in 2012,” he told the Wildlife Society. “The Mexican government shut it down, and we lost all of our investment as a nation.”

By May 2025, the USDA was looking at spending $21 million expanding sterile fly production again in Metapa, Mexico, and unveiled a $750 million plan to revitalize the Moore Air Base facility in August, due to building anxieties about the screwworm’s northward spread. The outbreaks were reported in Panama in June 2021. By August 2024, New World screwworm had been reported in Honduras. By November, the pest was back in Chiapas, Mexico.

“The Biden administration’s open border policies, combined with the Mexican cartel’s refusal to crack down on that through South and Central America, allowed the screwworm to move north for the first time in 50 years,” Rollins told the Senate Agriculture Committee on Wednesday.

One of the biggest names in Texas pointed the finger the other way. Democratic Senate nominee James Talarico cited “reckless cuts to the Department of Agriculture” made last year as a factor in spurring the latest outbreak, accusations echoed by Rep. Jimmy Gomez (D-CA).

“The screwworm monitoring program in Central America was cut by the Trump administration’s DOGE in early 2025,” Gomez complained this week. “Once again, this administration is desperately trying to downplay the problems they started.”

Regardless of who is to blame, industry leaders and officials say the situation appears to be under control.

TEXAS PREPARES FOR LOOMING SCREWWORM OUTBREAK: ‘THERE’S NOT A MAGIC BULLET’ 

The Texas and Southwestern Cattle Raisers Association, which boasts around 28,000 members, expressed optimism for the future, pointing to the resurrected Moore Air Base sterile fly facility set to come online next year, alongside the Metapa facility.

“We are going to get to that number of flies needed, which is 500 million and more with the genetically with the Novo fly, so I think that you know, of course, it can always be quicker, but we have every confidence in USDA and Texas Animal Health Commission,” TSCRA interim executive director of government relations Peyton Schumann said.