Op-Ed: New World Screwworm reaches South Texas, confirmed in Zavala County

The NWS larvae (maggots) burrow into (screw in) wounds of livestock, pets, wildlife and sometimes people. The more maggots, the more the animal is eaten alive. The parasite is endemic in Cuba, the Dominican Republic, Haiti and in South American countries. A current outbreak has been reported in Central America and Mexico.

Last June, the NWS was detected 700 miles south of Texas. By August, the NWS was detected 370 miles south of Texas, resulting in 94 state lawmakers calling on Gov. Greg Abbott to add NWS preventative measures to the special session agenda at the time. Abbott never did but he issued directives for state agencies to take action.

By last August, the USDA invested $750 million to build the first U.S.-based Sterile Screwworm Production Facility at Moore Air Force Base in Edinburg, Texas. Built with the Army Corps of Engineers, it’s plan was to produce up to 300 million sterile flies per week. It is the only sterile fly facility in the U.S. in a key location at the U.S.-Mexico border, The Center Square reported.

The USDA also announced a five-pronged plan to release hundreds of millions of sterile flies after spending $21 million renovating a fruit fly production facility in Metapa, Mexico. This facility is releasing 60-100 million sterile flies a week, in addition to more than 100 million produced in Panama, the USDA said last year.

By January of this year, Abbott issued a disaster declaration for the NWS after it was detected 70 miles south of Texas – building on directives he issued last June. 

State and federal efforts weren’t enough. By June 3, NWS was in Texas.

USDA Secretary Brooke Rollins held a media call Wednesday night with Texas animal health officials to provide an update and explain the “aggressive actions” being taken.

“Our food supply remains 100% safe. Screwworms do not infest meat, fruits, vegetables, or other food sources,” Rollins said. 

USDA Undersecretary Dudley Hoskins said their efforts had been successful in slowing the NWS from reaching Texas. “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, he said.

“Protecting our livestock industry is a national security issue of the utmost importance, and USDA is wasting no time in taking action. 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.”

The NWS was eradicated in the U.S. in the 1960s, experienced an isolated outbreak in the 1970s, and was ultimately eliminated after sterile flies were released along with other measures, The Center Square reported.

The USDA is urging producers and animal owners to follow movement restrictions and treatment guidance provided by the Texas Animal Health Commission. It’s working with the TAHC deploying response personnel, has established a 20 km infested zone around the area of detection, is implementing quarantines, movement controls, and surveillance in the affected area, it said. 

It’s also begun expediting targeted release of sterile NWS flies through ground release chambers in the area. It says four million sterile flies have already been released a week aerially in the area. 

It’s also increasing trapping for NWS flies along the border and outside of the dispersal area, implementing NWS surveillance and management strategies in wildlife and conducting targeted outreach in the local area, it said.

The USDA’s National Veterinary Stockpile is also providing assistance and resources, including treatments, equipment, and logistics support as needed. It’s also authorized the emergency use of Doramectin, an over-the-counter injection for livestock to prevent any infection.

Half a dozen cases of NWS were reported on June 1 in Nuevo Leon, Mexico, located between 50 miles and 70 miles south of the U.S. border. Nearly 30 cases were reported on May 31 in Queretaro, Mexico, according to the USDA’s tracking system.