By Julie Tomascik
Editor

New World screwworm (NWS) has been confirmed in Texas for the first time in decades.

State and federal animal health officials announced June 3 that the parasitic pest was detected in a three-week-old calf near La Pryor in Zavala County.

The detection marks the first confirmed case of NWS in the United States since the pest began moving north through Central America in 2023.

State and federal officials launched a joint response effort to contain and eradicate the fly.

A 20-kilometer infested zone has been established around the detection site, and animal movement restrictions are in place, according to the U.S. Department of Agriculture (USDA) and Texas Animal Health Commission (TAHC).

Increased surveillance, trapping and targeted releases of sterile male screwworm flies are also underway.

“TAHC has been actively preparing for a resurgence of NWS for over two years,” said Dr. Bud Dinges, TAHC state veterinarian and executive director. “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.”

USDA officials said years of preparation helped delay the pest’s arrival into the United States.

“All models showed New World Screwworm entering the country in 2025. However, thanks to the hard work across the entire Trump administration and our industry, state and local partners, we were able to buy time for this moment,” Dudley Hoskins, USDA undersecretary for Marketing and Regulatory Programs, said.

USDA immediately implemented response measures outlined in the agency’s New World Screwworm Playbook.

“Protecting our livestock industry is a national security issue of the utmost importance, and USDA is wasting no time in taking action,” Hoskins said. “USDA invested heavily in the tools needed to eliminate NWS ever since cases started increasing in Central America and Mexico. The United States has defeated this pest before, and we will do it again.”

Texas Farm Bureau President (TFB) Russell Boening said livestock producers should be aware of the detection but remain confident in ongoing eradication efforts.

“The confirmed detection of New World screwworm in Texas marks a new chapter for our state,” Boening said. “Texas livestock producers and all Texans must now be vigilant in their efforts to manage and combat the invasive pest.”

Boening noted TFB is working closely with state and federal partners as response efforts continue.

“Texas Farm Bureau is confident in the federal and state protocols established to again eradicate New World screwworm from Texas as was accomplished decades ago,” he said.

NWS is the larval stage of the New World screwworm fly. Unlike many maggots that feed on dead tissue, screwworm larvae feed on the living tissue of warm-blooded animals, including livestock, wildlife, pets and, in rare cases, humans.

Federal agencies stressed that the detection poses no risk to the food supply.

Officials encourage livestock owners, pet owners and wildlife managers to closely monitor animals for wounds containing larvae and immediately report suspected cases.

Additional information and situational updates are available at screwworm.gov.

Movement restrictions and potential quarantines will be posted on TAHC’s website.