USDA steps up screwworm monitoring as cases expand in Texas

The U.S. Department of Agriculture is stepping up its surveillance of New World screwworm, seeking to work with the Department of Homeland Security to contain a growing outbreak threatening the nation’s cattle herd.

Agriculture Secretary Brooke Rollins said in a Monday press conference that the two agencies were planning to enter into an official memorandum of understanding this week, which will establish a formal framework for greater collaboration on response efforts to a deadly parasite. The agency is also looking into utilizing dogs, drones and artificial intelligence to detect larvae and assess where animals may need inspection.

The increased monitoring comes as the parasitic fly has stretched beyond an initial control zone in Texas as the number of infections grows to a dozen, adding some urgency to efforts to contain the pest. The latest cases include a sheep in Sutton County and a head of cattle in Tom Green County, about 200 miles away from the first U.S. case in South Texas, according to the U.S. Department of Agriculture.

The agency is still looking into how that original case arrived in Texas, Rollins said. A “handful” of suspect cases in wildlife have been submitted, but all tests for the screwworm came back negative, according to Jason Suckow, director of the National Wildlife Research Center.

Further spread in Texas or in other states “would be a very bad milestone,” said Andy Moorhead, an associate professor at North Carolina State University. Moorhead, who also leads the American Association of Veterinary Parasitologists, said the conversation at the group’s annual meeting earlier this month was “nothing but screwworm.”

The planned agreement with the DHS is expected to strengthen the USDA’s monitoring efforts by combining the agencies’ workforces and technology to more efficiently combat screwworm.

The USDA is also looking into other fresh strategies, including employing dogs to sniff for larvae. Drones equipped with thermal imaging systems could also identify animals needing inspection, and help determine where to spread sterile flies, while AI-assisted smartphone apps could also be used to screen larvae in the field, Rollins said in the press briefing.

The additional measures come as the USDA works to ramp up its main weapon against the outbreak: churning out an army of sterile flies to halt reproduction of the parasite. But that strategy will take more than a year to reach its full effect, as a Texas facility for producing flies isn’t slated to begin operating until November 2027.

The screwworm is a fly that lays its eggs in the open wounds of warm-blooded animals. Its larvae burrow into flesh and can kill animals if left untreated. The initial case in Zavala County was the first in the U.S. in a decade and the first in domestic livestock in about five decades.

While screwworm doesn’t affect food safety, it poses a risk to the U.S. cattle industry, as drought and high production costs have culled the nation’s herd to a 75-year low. Restrictions on movement are likely to delay the rebuilding of the herd, which may send record beef prices even higher for consumers.

Under the restrictions, animals cannot be moved outside of the affected areas without authorization, and Texas Animal Health Commission representatives also need to inspect carcasses prior to removal from the zones.

The short-term movement protocols are already giving the state’s ranchers “many more advantages” than in the 1970s when the pest spread among 1.5 million head of cattle in Texas, said Stephen Diebel, the president of the Texas and Southwestern Cattle Raisers Association.

Diebel said he couldn’t speculate on the possible spread of the parasite, but said, “There’s very good measures in place with our existing fly production dispersals” that will keep producers in good shape until the output increases.

Still, some expect to see more cases of the parasite emerging. 

“This is easier to manage than it is to actually contain,” Jeff Simmons, Elanco Animal Health Inc. chief executive officer, said on Bloomberg Television on Monday. “We are going to see some of this spreading; this was expected.”

Arlan Suderman, the chief commodities economist at StoneX Group, said the U.S. will probably be “handicapped for a while” in its sterile fly dispersal, and even then, the spread will depend on how effectively those flies mate.

“My fear is that we’re talking about two to three years” to curb the spread, Suderman said. “But part of that depends on how many New World screwworms are already in the United States. The likelihood that there’s more is certainly there.”

With assistance from Katie Greifeld.

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