NCBA ' S FIGHT AGAINST NEW WORLD SCREWWORM

Photo courtesy of USDA.

The reemergence of the New World screwworm( NWS)— a parasitic fly capable of inflicting devastating wounds on warm-blooded animals— has reignited concerns across the U. S. cattle industry. In response, the National Cattlemen’ s Beef Association( NCBA) has launched a comprehensive mitigation plan rooted in policy advocacy, proactive prevention, and strategic partnerships.

In the rugged pastures of South Texas during the late 1960s, a young Bob McCan rode alongside seasoned cowboys on a mission to battle a silent, flesh-eating pest threatening the very heart of American cattle ranching: the New World screwworm.

“ I was about 11 or 12 years old,” McCan recalled.“ We had pasture riders on the ranch, and their main job was to check for screwworm infestations. We had a late outbreak during that time, and I remember treating baby calves with navel infestations. It was tough on them.”

The New World screwworm, Cochliomyia hominivorax, is a parasitic fly whose larvae feed on living tissue. For decades, it plagued livestock across the southern U. S., causing immense suffering and economic loss. McCan’ s memories offer a vivid glimpse into a time when ranchers had few tools to fight back.

“ We had one product— the old‘ 62 smear,’” he said.“ It was effective, but nasty stuff. Treating calves was tough, especially in the heat.”

But then came a turning point: the sterile fly program. The technique involved releasing millions of sterilized male screwworm flies into the wild. When they mated with females, no offspring were produced, gradually collapsing the population.

“ I remember seeing the boxes of sterile flies dropped in the pasture. We’ d be out on a ride and see that we had screwworms in a certain area and call it in. Then would come the plane to drop boxes of sterile files,” McCan said.“ Within days, the cases would drop off. It was incredibly effective.”

“ That experience sticks with you,” McCan said.“ Even as a kid, I understood how serious it was. The thought of having to battle that pest again— especially with how short we are on labor compared to the‘ 60s— keeps me up at night. We’ re enjoying a peak in the cattle market right now. A screwworm outbreak could derail that.”

The New World screwworm is more than just a nuisance— it’ s a threat that can devastate livestock and wildlife populations, causing immense economic damage. The pest not only affects livestock and wildlife, but also pets, birds, and in rare cases, people. Historically, uncontrolled infestations cost the U. S. livestock industry an estimated $ 100 million annually. Beyond the financial toll, the pest inflicts animal suffering and threatens food security and rural livelihoods. This is why the issue remains a top priority for NCBA.

Although the screwworm was officially eradicated from the U. S., the danger hasn’ t disappeared. The parasite remains endemic in parts of South America, and recent events have underscored the need for continued vigilance. Just last year, the threat resurfaced, proving eradication doesn’ t eliminate risk.

At the end of 2024, NCBA became the first national organization to sound the alarm when NWS was detected in Mexico. By July 2025, the U. S. Department of Agriculture( USDA) confirmed the pest’ s presence north of Veracruz— just 370 miles from the U. S. border.

In response, NCBA and state affiliate partners ramped up efforts to combat the threat. According to NCBA President Buck Wehrbein, the organization is pursuing a comprehensive strategy to protect cattle health. This includes collaboration across all levels— from individual farms and ranches to international partners— aimed at preventing a resurgence and safeguarding the industry’ s future.

Preparing for the Threat: Tools, Treatments and Teamwork Tools: Sterile Fly Program

NCBA’ s first priority— increasing sterile fly production, is a proven method for eradicating the pest. As McCan emphasized, the sterile fly program has historically been the most effective tool available. It remains the cornerstone of the industry ' s response. However, scaling up this technique has not been without challenges. From logistical hurdles to resource constraints, the path to full implementation requires coordinated effort, sustained investment and unwavering commitment.

“ We understand the problem and have a solution, but connecting the dots has proven challenging. We simply don’ t have the sterile fly production today that we need to feel comfortable about our ability to keep this pest at bay,” Wehrbein said.

6 NATIONAL CATTLEMEN DIRECTIONS 2025