Minnesota on alert after flesh-eating screwworm detected in the U.S.

A gruesome flesh-eating parasite, eradicated from the U.S. for decades, is once again casting a shadow over the nation’s livestock industry, and Minnesota officials are urging farmers and pet owners to be vigilant.

The New World screwworm, a maggot that feeds on the living tissue of warm-blooded animals, was recently detected in Maryland in a person who had traveled to El Salvador, the U.S. Department of Agriculture announced this week.

It’s the first reported U.S. case tied to travel to a country with a current outbreak.

The case is a “wake-up call” for Minnesota’s farmers, said Thom Petersen, commissioner of the state’s Department of Agriculture, in a phone call this week.

“We want farmers to take it seriously,” said Petersen, who recently spoke on a panel on the issue at Farmfest, an annual gathering of agricultural leaders in Morgan.

Some farmers believe that Minnesota is safe from screwworm infestation because of its cold winters, but the flies can probably survive in this state due to recent warmer temperatures, Petersen said.

The screwworm once was endemic in the U.S. until successful eradication programs that began in the 1950s dropped sterile male flies into Texas, Mexico and Central America to disrupt the reproductive cycle, eventually pushing the parasite south of Panama.

However, officials say cattle smuggling from South America has allowed the fly to migrate north again, with recent detections reported within a few hundred miles of the Texas border.

Minnesota imports a significant number of dairy cattle from southern border states, and the interstate movement of cattle is highly regulated, said Brian Hoefs, the executive director of the Minnesota Board of Animal Health.

The potential economic fallout from an outbreak could be severe. A screwworm infection in Minnesota cattle could cause international trading partners to “shut down trade,” Hoefs warned, slowing agricultural exports.

Should a screwworm case be detected in a state like Texas, Minnesota could implement even stricter protocols, potentially including preventive anti-parasitic medications, Hoefs said.

Hoefs described the chilling life cycle of a screwworm, in which the blue-gray adult flies lay eggs in wounds as small as a tick bite.

Telltale signs in animals include open wounds with maggots, strong odor, irritated behavior and tissue decay that expands and deepens over time. Infested animals usually separate from the herd, lie down and have visible discomfort or decreased appetite.

“It’s pretty, pretty nasty,” said Hoefs, who also spoke about screwworms at Farmfest. He said the Minnesota Board of Animal Health also created a fact sheet for producers and the public to learn more about the New World screwworm.

Federal efforts to contain screwworms include a $8.5 million sterile fly dispersal facility in South Texas, and the suspension of live cattle, horse, and bison imports from Mexico, Agriculture Secretary Brooke Rollins said in a prepared statement in June.

Hoefs said the case in Maryland highlights the threat of travelers bringing the parasite back home with them, noting a recent trend of people traveling internationally with their pets.

“The bigger threat to us here in the north … is going to be travelers that potentially are bringing the parasite back with them,” Hoefs said. “Dogs that travel with their owners are at risk of contracting an infestation.”