Veterinarians in Texas are on the alert for an invasive pest that can have a devastating effect on pets, livestock, and even people. The New World Screwworm (NWS) is a type of fly larva that can feed on living tissue in warm-blooded animals, including pets. While NWS is currently not present in the U.S., it has been rapidly moving through Mexico and was recently detected just 70 miles south of the border, making awareness and preventive care important for pet owners in Texas. While veterinarians are experts in animal health, we need the help of animal owners to successfully combat NWS by closely monitoring pets, livestock, and wildlife for signs of the disease.

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

The New World Screwworm is not currently present in the U.S., but understanding what it is and how to monitor your pets helps maintain their health and wellbeing. Routine care, careful monitoring, and prompt veterinary attention are effective ways to ensure your pets stay safe and healthy.

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.

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