New World screwworm has burrowed its way back into the United States after the flesh-eating parasite was eliminated here decades ago.

Since June 3, there have been 20 cases in the United States primarily affecting cattle — but one dog was diagnosed and successfully treated by a veterinarian in Texas.

Pet owners should be vigilant about watching their dogs and cats for signs of infestation by New World screwworm and keeping an eye on any wounds, according to Anne Kimmerlein, DVM, MPVM, DACVPM, global veterinary epidemiologist at Mars Veterinary Health .

“New World screwworm is actually a fly whose larval form — or maggots — will actually feed by burrowing into live tissue or flesh, which is sort of unusual,” she said. “Most of the maggots that we see usually only feed on dead or dying tissue. So it’s one of the reasons that this one’s kind of become a big deal.”

While New World screwworm infestations typically occur in wounds, larvae can also hatch and start to feed around the eyes, nose, mouth, genitals and rectal area, she noted.

“Basically, anywhere you have what we would call mucosal membranes — that tissue that’s a little bit moist there — they can unfortunately infest there as well,” she said.

How New World Screwworm Harms Pets

Any warm-blooded animal can be infected with New World screwworm, though it’s uncommon in birds and “really rare” in people, according to Dr. Kimmerlein.

Left untreated, a New World screwworm infestation can be fatal in 7-14 days .

“Unfortunately, they can feed pretty quickly and so they can turn what might’ve started out as a very small wound — or maybe not even a wound at all — into a pretty big wound pretty rapidly,” she said. “That’s one of the reasons that it’s important if a pet owner has any sort of sign or worry that their animal might have an infection with New World screwworm, it’s really important to go to the vet very quickly and get it diagnosed and treated pretty quickly so that things don’t get significantly worse.”

How To Protect Pets From New World Screwworm

The best thing for people to do is proactively monitor pets after they come in from outside for any cuts or scratches, according to Dr. Kimmerlein. Wounds that suddenly start to become larger or appear red or inflamed, or have any discharge or odor, could be signs of a New World screwworm infection.

Anything that looks like eggs or larvae around the wound, eyes or nose are a compelling reason to see a veterinarian.

“If you do see any wounds, get them into the vet quickly to have them cleaned and treated,” she said. “Then you’re going to want to limit the time that pets spend outdoors or near livestock — anywhere the flies are more likely to be.”

She recommends calling your veterinarian beforehand to let them know you have a possible New World screwworm case so they can make any preparations for your pet’s arrival, such as protective equipment or checking with the state veterinarian or U.S. Department of Agriculture (USDA) to make sure they are getting all the information they need.

“Because this is such an important disease for agriculture, for our economy, for public health, it’s what’s called a ‘nationally notifiable disease,’ which means that any veterinarian that has a suspect case needs to report it,” she said. “It’s good to give them a heads up in advance and that way they can prepare.”

Keep in mind that you’re unlikely to be infected with New World screwworm by your pet, since the most likely way for infection to spread is from the flies being present, Dr. Kimmerlein noted.

Do not attempt to remove the maggots from your pet at home.

“This is a reportable disease, and so veterinarians need to very carefully keep track of all the maggots and make sure they’re disposing of them properly so that it doesn’t continue to spread,” she said.

Because foxtails and other grass awns can cause small punctures that could attract New World screwworm, Dr. Kimmerlein advises keeping pets away from them. If you live in an area where there have been cases of New World screwworm, keep pets indoors, and make sure you have screens on all your windows — keeping the front door shut as much as possible.

Avoid traveling with pets to areas where there are known cases of New World screwworm, she added. For USDA updates about New World screwworm, including the location and species of cases, visit screwworm.gov .

Ultimately, Dr. Kimmerlein feels while it’s important for pet owners to be aware of the situation and do their part to help prevent the spread of New World screwworm, it’s also not cause for panic.

“It’s important to remember that the risk to the majority of pets is really, really low at this point,” she said. “I think it’s good to be aware, but certainly not to panic.”