Flesh-eating screwworms are spreading in Texas. Here's how to spot the signs in your pet.
It's now been more than a month since federal health officials first reported that a flesh-eating New World screwworm was detected in a calf in Zavala County, Texas. The presence of the pest has spurred action from the U.S. Department of Agriculture (USDA) and from Texas health officials.
Part of the response includes guidance for pet owners in the state should the screwworm impact their own animals.
Here's a breakdown of what you need to know about this pest and how to keep your pets safe and healthy.
What is the New World Screwworm?
The first thing to know is that the screwworm isn't really a worm; Texas A&M's AgriLife Extension notes it's a parasitic fly native to the Americas, though the name refers to the maggots that hatch from its eggs. The screwworm has been present in the United States before, but AgriLife Extension notes it was eradicated in the country through the mass release of sterile male flies.
More recently, however, the screwworm was detected in late May 2026 in Mexico, just 25 miles from the Texas border. After that, cases began popping up in New Mexico and southern Texas. The USDA's online dashboard for confirmed screwworm detections notes that as of July 7, 2026, six counties in Texas report active cases:
- Terrell County
- Crockett County
- Edwards County
- Uvalde County
- Medina County
- Jim Hogg County
The locations of these counties on the USDA dashboard align with a map published by the Texas Animal Health Commission (TAHC), which shows infested zones and adjacent surveillance zones near cities and towns such as San Angelo, Ozona, Uvalde, and Hebbronville.
Six other counties in Texas are now inactive as of publication, as is one county in eastern New Mexico.
What makes the screwworm dangerous?
AgriLife Extension says the screwworm lays its eggs in the living tissue of fresh wounds in warm-blooded animals. The larvae (maggots) then feed on the animals' flesh, which can lead to death if left untreated. The maggots' feeding causes damage because they have sharp mouth hooks that enlarge and deepen wounds as more eggs hatch.
Beyond injury to animals, AgriLife Extension says screwworms can cause economic losses when they affect livestock. While the USDA notes the screwworm doesn't affect food safety, it can devastate meat production.
While most focus is placed on livestock, concerns about the screwworms also extend to pets. So much so that CBS News Miami reports the state of Florida blocked the acceptance of rescue dogs and cats from Texas and New Mexico in mid-June.
What should Texas pet owners know?
AgriLife Extension says it's important to keep a close eye on all animals for key signs that the New World Screwworm may be present. The first thing to monitor is any open wound an animal has. Pet owners should inspect wounds for larvae.
Animals dealing with a screwworm infestation may be uncomfortable or irritated, and AgriLife Extension says they may also appear depressed or isolated from other animals or people. Affected animals may also have a lack of appetite, shake their heads, have a foul odor, or show other evidence of a fly strike.
AgriLife Extension says pet owners should check their animals daily, especially if they've had tick bites previously. Pet owners should also check the pet's environment for potential hazards, such as metal collars or chains, wire fencing, or sharp vegetation. Animals with outdoor access should also be kept from engaging in risky behavior, such as fighting, accidents, or aggressive incidents.
If pet owners believe their pet has larvae in a wound, AgriLife Extension says they should contact a veterinarian immediately. The vet should then remove and kill all larvae before cleaning suspect lesions and wounds. Veterinarians can also submit up to 10 maggots to the National Veterinary Services Laboratories for identification.
For further treatment, AgriLife Extension says certain medications can be used in both dogs and cats. Pet owners will need to discuss this with their veterinarians.
Beyond consulting with a vet, pet owners should also call the TAHC at 1-800-550-8242. Anyone who encounters a screwworm infestation in wildlife should contact their local Texas Parks and Wildlife Department's wildlife biologist or call 512-389-4505. Any human experiencing an infestation themselves should immediately contact their healthcare provider.