USDA has now detected five U.S. cases of New World screwworm since June 3. On June 7, officials confirmed NWS in a La Salle County, Texas, calf. That same day, screwworm was also confirmed in a dog in Lea County, N.M., which is the first confirmed case outside of Texas.
According to Dr. Bud Dinges, executive director of the Texas Animal Health Commission, a New Mexico man brought his dog to a veterinarian in neighboring Andrews County, Texas, on June 6. While officials are working to confirm details, they believe the man recently had his dog with him in Mexico.
On June 8, USDA confirmed another case in a goat in Gillespie County, Texas, which is about 140 miles from the Mexican border.
“These developments obviously represent a serious threat to our livestock and wildlife, but they haven’t caught us off guard,” Agriculture Secretary Brooke Rollins said during a June 8 press conference at the Knipling-Bushland U.S. Livestock Insects Research Laboratory in Kerrville, Texas. “We have been tracking this pest for a long time, and we have fought before, and we will do so again.”
What is USDA doing?
Rollins said USDA has been anticipating the return of New World screwworm for well over a year. Last year, the agency deployed more than 8,000 surveillance traps along the U.S.- Mexico border. Since January 2025, the agency has examined 59,000 fly samples and over 19,000 wildlife specimens. In addition, USDA has increased mounted patrols and trapping efforts along the border. Dogs have also been trained to detect flies in companion animals that cross the border.
USDA’s most powerful tool against NWS remains sterile flies, which mate with wild screwworm flies, causing the population to collapse. North America’s only sterile fly production facility is in Panama. It produces about 100 million flies per week.
Last year, the U.S. invested $21 million that would allow a fruit fly facility in Metapa, Mexico, to produce an additional 60 million to 100 million sterile flies per week. That facility is expected to begin producing sterile flies later in June.
This year, USDA broke ground on a $750 million sterile fly production facility at Moore Air Base in South Texas. When complete, it is expected to produce up to 100 million sterile flies per week. Rollins said that facility should open in mid-2027.
Additional efforts to combat screwworm
In May, USDA opened the Knipling-Bushland Laboratory in Kerrville. Rollins said the facility promises to provide “the world’s most cutting-edge research capabilities” for NWS.
Scott Hutchins, undersecretary for research education and economics, said it will be used to develop future tools to fight screwworm.
“We have 100% confidence in the sterile insect technique. It was developed by the namesakes of this laboratory, Dr. [Edward] Knipling and Dr. [Raymond] Bushland, in the ’40s and ’50s,” Hutchins said. “They did all they could do, but the tools that we have today and the opportunities that we have today to really build on and amplify that activity is really stunning to study.”
One potential breakthrough could be the development of the NovoFly. Through a new fly production process, USDA may soon be able to produce only male flies. The current production process produces both male and female flies. However, only sterile male flies impact the wild screwworm fly population. By producing only male flies, USDA could effectively double the number of sterile flies to fight screwworm outbreaks.
Is USDA’s response adequate?
In recent interviews, Texas Agriculture Commissioner Sid Miller criticized USDA’s screwworm response as “slow” and “inadequate.” He said USDA’s reliance on sterile flies is only a partial solution that will take years to implement. Miller argued USDA should pair sterile fly dispersals with the Screwworm Adult Suppression System, commonly referred to as SWASS. This method uses targeted bait to kill adult screwworm flies.
The commissioner has also warned that many ranchers may not report potential screwworm cases because they don’t want the government to restrict cattle movement. When asked about those fears, Rollins offered an uncharacteristically blunt response.
“That is a very unserious comment from perhaps an unserious ag commissioner with just a few months left,” she said. “It is also a very dangerous suggestion.”
Miller, a Republican who has been state ag commissioner since 2015, was soundly defeated in his March primary election. Texas Gov. Greg Abbott endorsed his opponent, Nate Sheets.
Miller stood by his comments, saying ranchers have personally told him they will not report for fear of being quarantined. While urging all Texas producers to report suspected cases, he also called on USDA and the Texas Animal Health Commission to revise current policies, which he says discourage reporting.
“Secretary Rollins’ name-calling is disappointing,” Miller told Farm Progress on June 8. “My team and I will stay focused on protecting Texas agriculture, not trading insults. We led the fight against New World screwworm from the start, and we’ll keep leading it.”
What about SWASS?
Hutchins said scientists are aggressively working to discover specific scents that attract female screwworm flies. This could potentially allow them to create what Hutchins refers to as “modern SWASS.”
He said the lure and materials for insecticides used in the past are no longer viable. Instead, USDA is focusing on developing new materials that focus on eradicating screwworm without any collateral impact to the environment. Scientists are also developing more precise modeling techniques and using artificial intelligence to better understand screwworm fly movement.
“To be sure, we do have big challenges ahead, but we’re committed to developing the tools and developing the techniques that will allow us to win this fight in the short run, and also specifically in the long run,” Hutchins said.
What comes next?
On June 8, President Donald Trump appointed John Bellinger to serve as the administration’s new senior adviser for NWS preparedness. Among other responsibilities, Bellinger will be tasked with exploring all available technologies to combat screwworm.
Abbott has also declared a state of emergency in Texas, which authorizes additional resources from all state agencies to combat screwworm.
As for where USDA plans to deploy its resources, Rear Adm. Michael Schmoyer, who leads USDA’s New World Screwworm Directorate, said those decisions will be guided by science. When the first U.S. case was reported the first week of June, the agency dispersed sterile flies in the area the following day.
Going forward, based on where cases arise, Schmoyer said his team is committed to doing the best and fastest thing they can do.
“You want to get this over quicker?” he asked. “Have people report. Ask people to report. Beg people to report. That’s what we need.”
