How to protect your pets from the New World screwworm fly

Veterinarians and humane societies are warning pet owners to be vigilant following the reappearance of the New World screwworm in the United States. More than 30 cases have been confirmed in cattle in Texas and New Mexico, with two recent instances involving dogs, prompting urgent advice on protecting animals.

The New World screwworm fly's larvae, which feed on live flesh rather than dead tissue, have not been widely present in the U.S. for over 50 years. The parasite's migration north from Panama starting in 2024 and through Mexico in 2025 poses a significant threat not only to the $113 billion U.S. cattle industry but also to any mammal. This includes wildlife, domestic pets like dogs and cats, and even humans, as the fly lays its eggs in open wounds or mucus membranes.

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It will kill the larvae as they ingest the blood and tissue. The chemical compositions of those products are what kill the actual larval stages of these flies.

Animal health experts advise pet owners in affected areas, southern and southwestern Texas and southeastern New Mexico, to conduct regular checks for wounds, cuts, or bites on their pets. Signs of infestation can include restlessness, a foul odor emanating from a wound, or the animal exhibiting obsessive chewing or licking in a specific area. The presence of maggots or any movement within a wound warrants immediate veterinary attention, as infestations can cause severe pain, shock, and potentially deadly infections.

To prevent infestations, shelters across Texas are administering prescription flea and tick medications to animals. Veterinarians and humane society officials recommend that pet owners do the same. These medications are effective because their chemical composition kills the screwworm larvae upon ingestion of blood and tissue. Prompt veterinary treatment is also available for infested animals, offering a chance for recovery if addressed quickly.

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Any one of those is reason enough to go to a veterinarian. The affected animal is likely in a great deal of pain, and that can cause death from shock.