When a sheep farmer in southern Texas noticed one of his animals listless and losing weight, a closer look revealed the grim culprit: writhing larvae burrowing into living flesh. The parasite was New World screwworm, a nightmare for livestock owners and veterinarians alike. Now, with 12 confirmed cases in domestic animals across Texas and one county in New Mexico, federal agencies are mobilizing fast to stop its spread before it takes deeper hold.
This flesh-eating larva, the offspring of a fly that lays eggs in open wounds, causes a condition called myiasis—inflicting severe pain, tissue damage, and, if untreated, death. While the parasite primarily threatens animals like cattle, goats, and pets, it can also infect humans through exposed wounds. Fortunately, no human cases have been reported in the U.S. this time, and the CDC says the public risk remains low. Crucially, the parasite doesn’t spread from animal to animal or person to person—infestation only occurs when flies directly deposit eggs into an open wound or body opening.
In a swift move, the CDC activated its Emergency Operations Center to coordinate with the USDA and Texas health officials. On the treatment front, the FDA made a pivotal decision: authorizing the first-ever generic drug for screwworm in pets. Generic nitenpyram tablets are now available over the counter for dogs, puppies, cats, and kittens, offering a fast-acting solution that kills most larvae within hours. The treatment requires two doses, six hours apart, though it doesn’t prevent reinfection. Veterinarians may still need to remove any remaining larvae, and owners are advised not to use the drug in animals under 2 pounds or younger than 4 weeks.
"Generic animal drugs build resilience in our domestic supply chain and play a critical role in expanding the toolkit of U.S. veterinary drugs for New World screwworm," said Timothy Schell, director of the FDA’s Center for Veterinary Medicine. The move not only speeds access but lowers costs for pet owners and ranchers facing an urgent threat. Still, prevention remains key—prompt wound care, vigilant monitoring, and immediate reporting of suspicious symptoms to state health authorities can make the difference between containment and outbreak.
New World screwworm was eradicated from the U.S. decades ago through coordinated releases of sterile flies, a strategy that suppressed reproduction. Officials now aim to replicate that success. With fast diagnostics, accessible treatment, and interagency collaboration, this resurgence may yet be short-lived. For now, the message to rural communities, pet owners, and veterinarians is clear: stay alert, act fast, and protect every open wound—because in the fight against screwworm, time is tissue.