Texas Parks and Wildlife confirms New World screwworm case in Zavala County

ZAVALA COUNTY, Texas (KVIA) -- Texas officials have confirmed the state's first case of New World screwworm in more than two years after the parasite was detected in a calf in Zavala County.

The Department announced Tuesday that laboratory testing confirmed the presence of New World screwworm larvae in a three-week-old calf with an umbilical lesion. The sample was identified by the National Veterinary Services Laboratory in Ames, Iowa.

State officials said no additional cases have been detected in Texas.

The detection marks the first confirmed case in Texas since the pest began moving northward from Central America in 2023. The Texas Parks and Wildlife Department is working with the U.S. Department of Agriculture, the Texas Animal Health Commission and other state agencies as part of a joint response effort.

The Texas Animal Health Commission has established an infested zone in the area and implemented animal movement restrictions to help prevent the parasite from spreading.

“NWS can have devastating impacts on free ranging wildlife populations and rural communities,”, Texas Parks and Wildlife Department Executive Director Dr. David Yoskowitz said. “TPWD, in partnership with our state and federal partners, will work diligently to respond to suspected cases of NWS, and to urge the public to monitor and report signs of an infestation in warm blooded animals.”

State officials said preparations for a possible return of the parasite have been underway for years.

“TAHC has been actively preparing for a resurgence of NWS for over two years,”, Texas Animal Health Commission State Veterinarian and Executive Director Dr. Bud Dinges said. “We are putting these preparations into action, and we encourage all animal owners and caretakers to continue to remain vigilant for the presence of larvae in animal wounds and immediately report any suspicions.”

According to the USDA, the nation's food supply remains safe. Officials said New World screwworms do not infest fruits, vegetables, grains or rice, and federal food safety inspectors continue to oversee the safety of meat, poultry and egg products.

New World screwworms are the larvae of the New World screwworm fly, a parasitic insect that lays eggs in open wounds or body openings of warm-blooded animals. After hatching, the larvae burrow into living tissue, causing a painful condition known as myiasis.

The pest primarily affects livestock but can also infest pets, wildlife and humans.

Officials said targeted releases of sterile screwworm flies are being accelerated in the area. The technique, which involves releasing sterile male flies to prevent reproduction, has historically been used to successfully control and eradicate screwworm populations.

Authorities are urging livestock producers and animal owners to closely monitor animals for signs of infestation and keep wounds clean and covered. Any suspected cases should be reported immediately to the Texas Animal Health Commission, and animals should not be moved until officials provide guidance.

Yoskowitz said public awareness and rapid reporting will be critical to preventing the parasite from becoming established in Texas.