06/04/2026
Update on New World Screwworm in Texas: Horse owners should closely monitor their animals for any wounds, as these flies can lay eggs in even small injuries. Early detection and prompt veterinary care are critical to preventing serious tissue damage. Please review the following information from the AAEP and contact us if you have concerns.
The U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) has provided an important update on New World Screwworm which has been detected in a bovine in Zavala County, Texas. Read the full press release here: https://www.aphis.usda.gov/news/agency-announcements/usda-confirms-presence-new-world-screwworm-united-states
General information about New World Screwworm (NWS) can be found in the text below and in the attached infographic.
The adult screwworm fly is about the size of a common housefly (or slightly larger), with orange eyes, a metallic blue or green body, and three dark stripes along its back. It gets its name from the behavior of its larvae (maggots) as they burrow (screw) into the wound, feeding as they go. The maggots (larvae) cause extensive damage by tearing at the hosts’ tissue with sharp mouth hooks. The wound can quickly become enlarged and deeper as more maggots hatch and feed on living tissue.
Because they feed on live flesh, NWS maggots may burrow deep into wounds or openings, while other species of maggots may appear around the outer surface of the wound. In addition, even the smallest wounds have the potential to attract flies, so it is imperative that you keep a close eye on your animals for any signs of wounds.
Lastly, NWS infestations are a reportable disease! Immediately report any suspicious wounds, maggots, or infestations to a local accredited veterinarian, your State Animal Health Official, or a USDA veterinarian.
For more information, reference this resource from the U.S. Department of Agriculture: https://www.aphis.usda.gov/animals/animal-health/livestock-and-poultry-disease/stop-screwworm
