When the first four New World screwworm cases in the United States in 60 years were reported in Texas, members of the American Association of Veterinary Parasitologists were already together at their annual conference.

Dr. Andy Moorhead, associate professor of parasitology at the NC State College of  Veterinary Medicine, was there in his role as president of the association and says, though the experts there were concerned, no one was caught off-guard.

“We’d been watching it inch closer and closer, but I guess while we weren’t exactly surprised that it jumped over, we hoped on some level it wouldn’t happen,” says Moorhead, noting that infestations have been moving northward from Central America since 2023. “Dealing with an outbreak is very different from dealing with prevention.”

Most parasitic flies lay eggs in carrion, naturally eliminating carcasses, but the New World screwworm lays eggs in open wounds or body openings of live warm-blooded animals. The resulting larvae then feed on living tissue, causing painful wounds, but a screwworm infection usually is fatal only if it goes untreated, Moorhead says.

As of Monday, 15 cases had been reported in or near Texas affecting cattle, two goats, two sheep and one dog. 

The good news, he says, is the parasite is not novel and has been eradicated in the United States before so officials already know what to do. 

“They sterilize and release millions of male flies, and eventually the flies are going to die out because there’s no offspring,” he says. “That’s why it’s so important we are using biology to our advantage. We know they only mate once and eventually that diminishes the ranks of them without having further offspring.”

The nation’s veterinary parasitologists are most concerned about suspect cases getting to the proper authorities for testing, identification and quarantine, Moorhead says. In most states, that would be the state’s department of agriculture.

The NC Department of Agriculture hosted a webinar this month to build more awareness that was heavily attended by the state’s veterinary community.

“In North Carolina, from pet owners, livestock producers and certainly veterinarians and everyone in the veterinary field, there is an awareness that this disease is in the United States, and that we need to be vigilant for it,” he says. 

Moorhead’s No. 1 piece of advice for North Carolinians is to keep up with the USDA New World screwworm website and dashboard, found here, and to make sure pets are up to date on all of their preventive medicines. 

No. 2 is that a call to your veterinarian is the first one to make if you have any concerns.