The USDA confirmed the case on June 8, 2026, in Lea County, New Mexico, alongside five cases in livestock across southwest Texas. The US eradicated New World screwworm domestically in 1966 — a multi-decade achievement that protected American livestock and pets. The parasite never fully disappeared from Central and South America, and it has now crossed back.

Dog owners with outdoor or free-roaming pets need to know the signs.

The name is not an exaggeration.

New World screwworm flies lay eggs in open wounds — including small cuts, insect bites, or surgical sites. The larvae burrow into living tissue and feed, expanding the wound as they grow. Without treatment, infestations cause severe tissue damage, organ failure, and death. The flies target any warm-blooded animal with a wound, which means dogs with even minor injuries are at risk.

Screwworm is not contagious between animals — the threat is the fly, not the dog.

A wound that won't heal is the first red flag.

Infestations present as a wound that worsens instead of improving — often with a foul odor, discharge, or visible movement inside the tissue. Dogs may repeatedly lick or bite at a specific spot, run a fever, lose their appetite, or become lethargic. In advanced cases, maggots are visible in the wound.

If you see any of these signs in a dog with an existing wound who spends time outdoors, call a vet the same day.

There is no approved preventative medication specifically for screwworm.

Flea and tick products containing afoxolaner, lotilaner, or sarolaner have shown activity against screwworm larvae and offer some protection. The FDA authorized emergency use of Nitenpyram as a treatment — it kills most larvae within hours of the first dose, with a second dose six hours later. Any remaining larvae must be physically removed by a vet.

The most effective protection is the simplest: keep wounds clean, covered, and watched closely.

The CDC and USDA describe the current US risk as low — but the outbreak is moving fast.

Cases spread from Texas livestock to a New Mexico dog in under a week, and the USDA has acknowledged the dog's travel history is still unknown, which means exposure points could be wider than confirmed. The AKC Canine Health Foundation notes that new interstate travel health requirements are now in place for dogs moving between states. Outdoor dogs, rescue dogs, and any dog with a healing wound are the highest-risk population right now.

This one is worth watching.

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