New World Screwworm: What US Dog Owners Should Know (October 2026)
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Updated October 16, 2026. New World screwworm, a parasite eradicated from the US more than 50 years ago, was detected again in June 2026. Most of the cases are in livestock, but a small number of dogs have been infected. Here's what dog owners need to know, without the panic.
What it is
New World screwworm is the larva of a fly, Cochliomyia hominivorax. Unlike ordinary maggots, which feed on dead tissue, these larvae feed on living tissue. The female fly lays eggs in open wounds and moist areas. Any warm-blooded animal can be affected, including dogs, cats, wildlife and, rarely, people.
Where it is right now
- As of October 15, 2026, Texas Public Radio counts 56 confirmed animal cases since June: 52 in Texas and 4 in New Mexico.
- Cases have been confirmed in Brewster, Crockett and Pecos counties in Texas, with movement restrictions in parts of 12 Texas counties, and in Grant County, New Mexico.
- A dog case in Brewster County, Texas was confirmed on October 2. Earlier dog cases were reported in Texas and New Mexico in July.
Cornell's veterinary college describes the risk for most pet dogs in the US as low. The highest-risk dogs are those in or traveling through affected areas who have an open wound, a recent surgery or another moist spot where flies can lay eggs.
Warning signs
- A wound that gets worse instead of better
- A foul smell from a wound
- Visible larvae or movement in a wound
- Restlessness, or your dog fixating on or chewing one spot
If you see any of these, call your vet right away. Treated early, dogs can recover. Screwworm is a reportable disease, so your vet will involve state animal health officials.
If you're traveling with your dog in Texas or New Mexico
- Check your dog daily for cuts, scrapes, tick bites and incisions, and keep wounds clean and covered.
- Ask your vet whether a prescription flea and tick product makes sense for your dog. Several have emergency authorization for treating screwworm in dogs.
- Avoid travel shortly after surgery if you're heading into an affected area.
- Crossing to or from Mexico? Check the current USDA APHIS and CDC rules before you go. Dogs entering the US from Mexico must be inspected and certified free of screwworm.
What's being done
USDA and state officials are releasing sterile male flies, the same method that eradicated screwworm from the US decades ago. The USDA has announced a new sterile-fly facility in Texas.
This article is general information, not veterinary advice. The situation changes quickly; follow your state animal health agency and USDA APHIS for the latest.