Once thought to be a problem of the past, the New World screwworm (Cochliomyia hominivorax) is once again raising concerns. With recent detections in Mexico and Central America, Texas A&M AgriLife Extension is mobilizing its research, teaching, and outreach power to help protect Texas livestock, pets, and wildlife.
Though this parasitic pest was eradicated from the U.S. in the 1960s through a groundbreaking sterile insect technique (SIT) program, its return to areas just south of the border is a clear warning sign. Texas ranchers, pet owners, and wildlife stewards must remain vigilant.
What Is the New World Screwworm?
This is no ordinary fly. The New World screwworm targets warm-blooded animals—including livestock, pets, and wildlife—by laying eggs in open wounds. The hatched larvae (maggots) burrow deep into tissue, causing painful, rapidly expanding wounds that often lead to secondary infections or death if left untreated.
The name “screwworm” comes from the spiral shape of the larva’s body spines and its gruesome habit of “screwing” into flesh as it feeds. These larvae can reach up to two-thirds of an inch in length. The adult screwworm resembles a metallic blue blow fly, with three black stripes on its thorax. It’s important not to confuse it with the secondary screwworm (Cochliomyia macellaria), which looks similar but does not attack living tissue.
If you spot a suspicious fly or larvae, take a photo and email it to:
[email protected]
How to Spot an Infestation
Animal owners should inspect their animals regularly. Early detection can save lives and stop the spread.
- Watch for these warning signs:
- Foul-smelling wounds crawling with white maggots
- Constant licking, biting, or scratching of wounds
- Lesions in vulnerable areas like navels, ears, or branding sites
- Lethargy or unusual restlessness
- Maggots with distinct spiral ridges and visible breathing tubes
Prevention Tips:
- Promptly clean and treat wounds
- Keep animal areas clean and sanitary
If Infestation Occurs:
- Carefully remove maggots
- Apply topical larvicides like coumaphos or permethrin
- Monitor for reinfestation and follow up with veterinary care
Report Suspected Cases Immediately:
- Your local veterinarian or wildlife biologist
- Texas Animal Health Commission: 1-800-550-8242
- USDA Veterinary Services: 512-383-2400
Do not move any potentially infested animals until given official guidance.
Stay Informed
AgriLife is actively providing resources and updates to help Texans stay ahead of this threat. Visit the
AgriLife Screwworm Resource Center for news, webinars, and more.
The New World screwworm isn’t just a pest—it’s a serious threat to animal welfare, the economy, and local ecosystems. With coordinated action and early detection, Texas can stay one step ahead.
For more information or to get involved, contact:
Dr. Phillip Kaufman
Professor of Entomology
[email protected] | 979-321-5812
Blair Fannin
AgriLife Communications
[email protected] | 979-803-1264
