Since June is Adopt a Cat Month, I normally write my four weekly blogposts in June specifically about cats. Today, I am breaking that tradition because of an important disease affecting both cats and dogs that has recently appeared in the United States: the new world screwworm (NWS).

For many months, the United States Department of Agriculture (USDA) has been warning Americans about the new world screwworm. This parasitic fly is in Central and South America, but recent cases have been moving north. Government officials have been predicting the arrival of the new world screwworm in the United States, and on June 3, 2026, it was identified in a calf in Texas for the first time in 60 years.

Please note: New World Screwworm’s arrive in the United States is an evolving situation. For the latest information and updates, please visit the USDA’s website.

What is the new world screwworm?

NWS is a parasitic fly that looks much like a common housefly. It lays eggs in open wounds. When the eggs hatch, the larvae, also known as maggots, burrow into the flesh of living animals.

Is the new world screwworm contagious?

Livestock, birds, dogs, cats and, rarely, humans can be infected with new world screwworm. However, it is not “contagious.” It does not transmit directly from one animal or person to another. It is only transmitted when the adult NWS lays its eggs and the eggs hatch into the flesh-eating maggots. Your pet cannot give you the infection, and you cannot give the infection to your pet. But, since you and your pet share the same environment, you could both be infected if you both come in contact with the egg-laying flies.

What does a new world screwworm infection look like?

NWS maggots are found in foul-smelling wounds, where they burrow into living tissue. These wounds can be as small as a tick bite.

Skin folds around the face, eye and neck; the mouth and ears; genital and anal areas; nails and paw; places where your pet licks excessively; and any recent surgical sites are all places where new world screwworms may lay eggs.

If your pet has a non-healing wound or visible maggots, your veterinarian should examine them as soon as possible.

If you have a non-healing wound, see your physician as soon as possible. New world screwworm infections must be reported to the USDA for animal infections and the local health department for human infections in order to track and eradicate the flies and larvae.

How big a threat is the new world screwworm?

This answer depends on where you live and whether your pet travels. NWS thrives in tropical and subtropical climates. With global warming and summer heating up, the new world screwworm’s habitat may be expanding.

Pets that travel to warmer climates may contract the infection and transport it home when they return. Hot, dry climates and cold weather are inhospitable to new world screwworms.

Can new world screwworms be treated?

Thankfully, veterinarians have treatment options for new world screwworm infections in dogs and cats. The FDA has issued emergency use authorizations and conditional approvals for certain medications to treat NWS in other species, including products many veterinarians already know from flea, tick and parasite prevention.

Not all maggots are new world screwworms, but all maggot infections in pets need veterinary care. Contact a veterinarian right away for any suspicious wounds, maggots or infestations in your pet. Early veterinary care protects your pet and helps animal health officials respond quickly if new world screwworm is involved.

How can I protect my pet from new world screwworm?

There are no preventative medications for new world screwworm. However, the risk remains low for most dogs and cats in the United States. The pets I worry about most are those living near affected areas or traveling to and from warmer regions where new world screwworm is active.

Be sure to check your pet regularly for wounds, especially after travel, surgery, grooming, outdoor adventures or tick bites. Pay close attention to the ears, mouth, paws, skin folds, genital and anal areas, and any place your pet is licking excessively. If a wound smells bad, drains, attracts flies, contains maggots or simply does not heal, call your veterinarian right away.