New World Screwworm case in South Texas calf

By Anthony Collins

LPR Editor                        

   Texas officials are moving quickly after New World Screwworm (NWS) was confirmed in Zavala County, marking the first detection of the pest in the United States since it was eradicated in 1966.

   The Texas Veterinary Medical Association (TVMA) recently alerted pet owners and livestock producers about the discovery, which was found in a calf in South Texas. While the case involved livestock; dogs, cats, wildlife, and other warm-blooded animals can also be affected.

   In response, Governor Greg Abbott issued a disaster declaration for Zavala and Uvalde counties and announced that all available state resources will be used to stop the spread. “We have eradicated this pest before, and we will do it again,” Abbott said during a briefing with state and federal officials.

   Despite its name, New World Screwworm is not actually a worm. It is a fly whose larvae feed on the living tissue of animals. If left untreated, infestations can cause severe damage and may even become fatal.

   While the discovery sounds alarming, animal health experts say there is no reason to panic. Texas has been preparing for this possibility for more than a year. In 2025, Governor Abbott directed state agencies to create the Texas New World Screwworm Response Team, bringing together veterinarians, livestock producers, wildlife experts, and federal agencies to develop response plans before any case was detected.

   State and federal officials are now using a proven eradication method known as the Sterile Insect Technique. Millions of sterile male flies are released into affected areas, where they mate with wild females. Because female screwworm flies only mate once in their lifetime, the eggs produced do not hatch, causing the population to decline naturally over time.

   Governor Abbott has also directed state agencies and Texas university systems to help speed up the movement of sterile flies into Texas and assist with construction of a new sterile fly production facility in Edinburg.

What Pet Owners Should Watch For

    Even small wounds, including scratches, tick bites, insect bites, surgical incisions, or newborn navels can attract screwworm flies.

     Officials recommend that Texans:

•Check livestock and pets daily for wounds or unusual skin problems. 

•Treat wounds promptly and keep them clean. 

•Watch for wounds that do not heal, foul-smelling discharge, irritation, or visible larvae. 

•Closely monitor outdoor pets, especially those with exposed wounds. 

•Report any suspected cases immediately and do not move the affected animal. 

   Wildlife can also be impacted. Residents who notice deer, feral hogs, exotic game animals, or other wildlife with unusual wounds are encouraged to notify Texas Parks and Wildlife. The good news is that New World Screwworm is highly treatable when caught early. With state and federal agencies already responding, officials remain confident Texas can once again eliminate the pest and protect the state’s livestock, wildlife, and pets.