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You have likely heard of the New World Screwworm recently discovered in Texas and New Mexico. This threat to livestock did not materialize overnight. Animal Health Authorities have been tracking this threat ever since it cropped back up in the Darien Province of Panama a couple years ago, and knew it was only a matter of time before it made it's way North through Central America, then Mexico and into the United States through the Southern border.
The New World Screwworm is a parasitic fly that deposits larvae, on the living tissue in or near open wounds of animals, where they burrow into the flesh and feed on live tissue as opposed to most maggots who feed on dead tissue. In fact, in the old days medical personnel have used maggots to debride wounds of soldiers and other patients to prevent gangrene. The New Word Screwworm is primarily a threat to livestock and other mammals such has pets, but the risk to humans is pretty low. Infected animals usually present painful, worsening wounds that may smell bad and fail to heal. Visible larvae in wounds, unusual discharge, and signs of distress in the animal are other potential indicators. If untreated, the infestation can lead to severe tissue damage, open up other infections, and even lead to death of the animal. Check your livestock and other anials routinely, treat and monitor wounds that you see and get ahold of you Vetrinarian if you suspect infestation.
The Texas Animal Health Commission (TAHC) public notice confirmed on 10 June 2026 that it (the TAHC) has designated multiple counties in South Texas as infested zones due to confirmed cases of the New World screwworm. These counties include Zavala, Uvalde, La Salle, Gillespie, Kerr, Kimble, and Webb counties (see map below). A quarantine is in place, meaning warm-blooded animals cannot leave these areas without inspection, treatment, identification, and a movement permit from TAHC authorities. Additional surveillance zones surround these infested areas to monitor potential spread. These zones are actively tracked, and updates are provided daily as new cases are confirmed.
Feedlots in West Texas feedlots are feeling the implications of this threat as border closures and restrictions on importing Mexican cattle have severely curtained their business. Eradication efforts are pretty straightforward and have been used for the past 70 years, and recently in Southern FLorida in 2017 by releasing sterile New World Screwworm male flies. Female New World Screwwom flies only mate once in their lifetime, so eggs laid by a female fly serviced by a sterlized male fly produces unfertilized eggs that do not hatch into the flesh eating larvae. Eventually no live larvae are hatched andn the New orld Screwwom population dies off.
Additional Resources:
Texas Animal Health Commission
U.S. Department of Agriculture National Invasive Species Information Center
