For the first time since it was eradicated from the country in 1966, New World screwworm was confirmed in the United States in June 2026 as the pest spread north through Central America and Mexico. It can infest livestock, wildlife, pets, and in rare cases people, so yes, dogs are at risk. Here is what it is and exactly what to watch for.
What New World Screwworm Actually Is
New World screwworm is the larva of a specific fly. What makes it dangerous is unusual: unlike ordinary maggots that feed only on dead tissue, screwworm larvae burrow into the living flesh of a warm-blooded animal, which is where the "screw" in the name comes from. A female fly lays her eggs at the edge of an open wound, and once they hatch the larvae eat their way inward, enlarging the wound and drawing more flies. The US eliminated it in 1966 and stamped out a small Florida Keys outbreak in 2017, but the 2026 detection means it is back on the radar.
How Dogs Get It
Any break in the skin is a possible entry point: a cut, a scrape, a tick-bite sore, a surgical incision, an ear infection wound, or even the navel of a newborn puppy. Dogs that spend time outdoors with untreated minor injuries are the most exposed. The wound does not need to be large. A small, damp, open sore is enough to attract the fly.
The Signs to Watch For
The tell is a wound that gets worse instead of better. Watch for a sore that grows over a day or two rather than scabbing over, a foul odor, bloody or brown drainage, visible maggots deep in the wound, and obvious pain or restlessness. Because the larvae tunnel inward, the opening on the surface can look smaller than the damage underneath.
Why It Is an Emergency
Screwworm can destroy tissue quickly and become life-threatening, and it is a reportable pest, meaning cases need to reach a veterinarian and animal-health authorities so spread can be tracked. Do not just flush it at home and hope. If you see maggots in a wound that is enlarging, get to a vet promptly.
How to Protect Your Dog
Check outdoor dogs regularly and treat even small wounds right away by cleaning them and keeping them covered until they heal. Watch surgical sites and newborn puppies closely. And know what is being reported near you, since screwworm risk is regional and moving. You can see current activity on the ParvoMaps outbreak map and read the full overview on our screwworm page.
Because screwworm risk moves with the outbreak, staying current on what is active near you is the best early warning. ParvoMaps tracks canine disease and pest reports in your area, and you can set up outbreak alerts so new detections reach you first.