Veterinarians across Texas are responding to the threat posed by the New World Screwworm (NWS), an invasive pest that can have devastating effects on pets, livestock, wildlife, and even people. On June 3, NWS was confirmed for the first time in the United States, in two calves in Zavala County. NWS is the larval stage of a fly that feeds on the living tissue of warm-blooded animals, causing serious and potentially life-threatening wounds if left untreated.

As Texas works to prevent the spread and impact of NWS, awareness and early detection are critical. Veterinarians play a key role in protecting animal health, but successful surveillance and response also depend on animal owners. Pet owners, livestock producers, and others who care for animals can help by closely monitoring animals for wounds or signs of infestation and promptly contacting a veterinarian if they have concerns. This guide provides Texas pet owners with more information on what to watch for, and how to report suspected cases. (Link to the guide currently linked down at the bottom).

Understanding the New World Screwworm

The NWS (Cochliomyia hominivorax) differs from common flies in that the larvae (maggots) feed on living tissue rather than dead tissue. Infestations typically occur in open wounds, including small scratches, insect bites, or surgical incisions. After the adult female fly lays eggs near an open would, the eggs hatch and the NWS larvae burrow into the animal’s body, eating the underlying tissue and causing severe pain as well as secondary bacterial infections. Prompt veterinary attention is required to ensure proper treatment and recovery, as NWS infestations are painful and can be fatal if left untreated.

Signs to Monitor

Pet owners should keep an eye on their pets, livestock, and wildlife in their area for:

• Wounds or sores, even minor ones, which can serve as a site of infestation
• Swelling, discharge, or changes in skin around a wound, either with or without the presence of visible NWS larvae.
• Foul odor. Infested wounds have a very distinctive, strong smell.
• Pets licking or chewing at a wound more than usual
• Changes in appetite or activity levels

Regular checks help identify issues early and allow for timely veterinary care.

 What to Do

If you notice any concerning signs, contact your veterinarian. Veterinarians are trained to examine wounds, provide appropriate treatment, and can coordinate with the Texas Animal Health Commission if needed.

Preventive Measures

To reduce the risk of NWS exposure:

• Regularly inspect pets for any cuts or scratches
• Keep wounds clean and covered
• Follow your veterinarian’s guidance on insect protection
• Be aware of areas with reported infestations when traveling

On June 3, 2026 the first case of New World Screwworm (NWS) was confirmed in a three-week-old calf in Zavala County, Texas. Other than an isolated incursion in the Florida Keys in 2016, this marks the first detection of NWS in the United States since the pest was eradicated in 1966. State and federal animal health officials are actively responding.

While this detection is significant, there is no reason for alarm. The U.S. Department of Agriculture (USDA), the Texas Animal Health Commission (TAHC), veterinary professionals, and livestock industry partners have been preparing for this possibility for more than a year. Sterile fly dispersal operations are already underway in South Texas, surveillance systems are in place, and effective treatments are available. The United States successfully eradicated New World Screwworm in the past, and today’s response tools are even more advanced.

Pet owners can help protect their animals by staying informed, routinely checking pets for wounds or unusual skin conditions, and seeking prompt veterinary care if concerns arise. Routine preventive care, regular monitoring, and timely veterinary attention remain the best ways to support your pets’ health and wellbeing.

Texas Veterinary Medical Association created this flyer as a quick resource to help pet owners learn about NWS infections. It explains how these infections occur, what signs to watch for, and why prompt veterinary care is so important. Your veterinarian is sharing this information to help protect your pets through early detection and prevention.

---

| About the Author |