New World screwworm is back, and it can kill pets. How to treat it in NC
AI-generated summary reviewed by our newsroom.
- Screwworm larvae feed on living mammal tissue and can cause deadly damage if untreated.
- As of June 10, six U.S. cases were confirmed, five in Texas and one in New Mexico.
- The FDA authorized emergency use of generic nitenpyram tablets for eligible pets.
The New World screwworm, a parasitic fly that lays eggs in open wounds on mammals and eats living flesh, was found in a dog in New Mexico Monday, June 8.
The New World screwworm is a parasitic fly that feeds on the living flesh of mammals and rarely, people. NC State College of Veterinary Medicine Research Associate Professor Barbara Qurollo said risk to North Carolina pets remains low, but state authorities are vigilant. She researches vector borne diseases.
“Right now the risk to dogs and cats is pretty low, unless they’ve had a travel history, so unless they’ve been to some of these sites where they’ve detected the screw worm and even overseas, like in Mexico,” Qurollo said.
The infected dog had recently visited Mexico. While the screwworm is generally found in the Caribbean and South America, it has been identified moving Northward in Mexico since 2023, according to the USDA.
As of Wednesday, June 10, six cases are confirmed in the United States. Five are in Texas, and the sixth is the dog in New Mexico. The dog was originally reported as a Texas case, and its travel history is being investigated, according to NC State.
The New World screwworm was eradicated in the United States in the 1960s, and Qurollo said she believes adequate preventative measures are being taken.
“It doesn’t make me nervous right now, because they’re doing a lot of surveillance, and there are a lot of steps being taken now to try to mitigate this,” Qurollo said.
Screwworm infestation symptoms
NC State Veterinary Medicine said farmers and pet owners should look out for:
- Maggots or white egg masses in wounds or body openings, including the nose, ears, genitalia or the navel of newborn animals.
- A foul odor or the smell of decay.
- Signs of pain, such as irritability, not eating, depression or pulling away from the rest of the herd.
“I would advise owners to look over their pet really well for any little wounds, even a tick attachment. A wound from a tick attachment could be a site where the New World fly could lay her eggs,” Qurollo said. “When the eggs hatch, they become larvae. These larvae feed on living tissue, so that’s what’s different from these maggots than other maggots that we’re more familiar with, which feed on dead tissue.”
Qurollo recommends keeping pets up-to-date on flea and tick medication to prevent wounds where flies may lay eggs.
FDA Authorization
The FDA issued an Emergency Use Authorization for generic Nitenpyram Tablets for the treatment of New World screwworm infestations in dogs, puppies, cats and kittens that weigh at least two pounds and are at least four weeks old. Nitenpyram is the first generic animal drug authorized for use against screwworms, according to the FDA.
Nitenpyram kills most larvae within hours of the first dose. Pet owners should administer a second dose six hours after the first. The medication does not prevent myiasis (infestation of eggs and larvae) or protect against reinfestation. Following treatment, a veterinarian may need to remove any remaining live or dead larvae. The tablets are available over the counter.
Qurollo said while screwworms can cause serious and even deadly damage, they are treatable in both pets and livestock.
“It’s about catching it early enough, and so that’s why I would say, keeping your eye out for any, any little wounds, if your animal does have a wound, covering it, making sure that it’s not available to the fly to lay eggs,” Qurollo said. “And again, the risk to owners right now in North Carolina is low.”
Reporting
New World screwworm is a reportable disease in the United States; suspected cases must be reported to animal health officials.
In North Carolina suspected cases can be reported to the North Carolina Department of Agriculture and Consumer Services Veterinary Division at 919-707-3250. Veterinarians report to the USDA Area Veterinarian in Charge.
