Rollins ramps up New World screwworm protection efforts

If you started ranching within the last five decades, it’s unlikely that you’ve seen a case of New World screwworm because the deadly parasite was largely eradicated from the United States in 1966 and has rarely been seen since.

However, cases of NWS in Panama exploded in 2023 from an average of 25 cases reported per year in Panama up to 6,500 in 2024, according to U.S. Department of Agriculture’s Animal Plant Health Inspection Service. Since that time, the parasite spread throughout Central America to Costa Rica, Belize, Nicaragua, Honduras, Guatemala, and El Salvador.

In November, NWS was found in a cow at an inspection checkpoint in the southern Mexican state of Chiapas, near the Guatemalan border—the first positive case in Mexico since the early 1990s. USDA soon shut the Mexican-American border to live animal trade. Since that time, the border reopened, but was shut down on July 9 after new cases were detected in Oaxaca and Veracruz.

The risks associated with a NWS outbreak in the U.S. would be huge, both for ranchers and consumers already dealing with higher beef prices. Texas cattle feeders have typically relied on Mexican animals for about 15% of their supplies.

During the 20th century, the pest was annually responsible for $100 million of damage in the U.S (not inflation-adjusted), according to the Texas Animal Health Commission. The commission estimates that the cost to eradicate NWS from the U.S. today, if it reappeared, would be around $1.27 billion.

Rollins responds

Agriculture Secretary Brooke Rollins recently announced new steps to prevent New World screwworm from reaching the U.S. while acknowledging that beef prices could continue to rise amid the suspension of Mexican cattle imports. 

Speaking at a news conference with Texas Gov. Greg Abbott, Rollins said the border wouldn’t be reopened until she received assurances that the outbreak of the flesh-eating pest in Mexico is under control.

“We’ve got a lot of work to do, but we have to protect our cattle industry and our beef industry in this country, and in so doing protect our food supply, and in so doing protect our national security for America,” Rollins said.

“Do we expect beef prices to continue to rise, perhaps, but the safety and the security of our beef and our ranchers has to be at the top of the list.”

Beef prices rose 1.5% in July alone and are up 11.3% since July 2024 amid tight U.S. beef supplies.

She said the pest “endangers our livestock industry, and it threatens the stability of beef prices for consumers across America.”

Sterilization is key tactic

In past decades, eradication of the NWS was made possible by breakthroughs at the Agricultural Research Service, when scientists discovered how to sterilize male flies using radiation in the first half of the 20th century. Because female screwworms mate only once in their lives, this presented an opportunity to disrupt the life cycles of the flies and eliminate them from areas where they’d been wreaking havoc for years.

Rollins’ latest steps for combatting the pest include spending up to $750 million on a new facility for producing sterile flies in Edinburg, Texas, on the Mexican border. The facility is supposed to produce up to 300 million flies per week.

In June, Rollins announced plans to open a new sterile fly dispersal facility at an inactive Air Force base in south Texas near Edinburg. That $8.5 million facility, located about 20 miles from the U.S.-Mexico border, will be completed in 2025 and have the capability to disperse flies in northern Mexico, according to USDA.

USDA is putting up to $100 million into new technology for screwworm control, including new types of traps and lures, she said.

“I’m calling on the brightest in the country to build on our existing tools and help us outpace this pest quickly and in the most innovative way possible,” Rollins said.

USDA also is concerned about wildlife bringing the screwworm across the border and to that end Rollins said the department would hire additional mounted officers, historically known as Tick Riders, to patrol the region. The mounted patrols will be “the cornerstone of our surveillance program,” she said.

Rollins said Mexico has agreed to “halt animal movement in infected zones, which will help push screwworm back towards Darien Gap (the border area between Panama and Colombia) and away from our doorstep.”

Texas Ag Commissioner Sid Miller said there needs to be evidence that the screwworm population is being pushed back southward before cattle imports can resume.

“If we can show that it’s not only stopped, but it’s regressing, and we’re moving it back, that is the point where we could consider opening up the border, but we have to have full cooperation with Mexico before that can happen,” he said.

Miller’s department recently reintroduced a 1970s method to control the pest, Swormlure bait, which attracts adult screwworm flies by using synthetic chemicals that mimic fresh wounds and is often combined with insecticides to kill the flies. Miller said the bait will be time-released and should be effective for up to four weeks.

On Aug. 19, the U.S. Department of Health and Human Services also joined the NWS battle by issuing Emergency Use Authorizations for animal drugs to treat or prevent infestations caused by the NWS.

“Today we are taking decisive action to safeguard the nation’s food supply from this emerging threat,” said HHS Secretary Robert F. Kennedy, Jr. “This authorization equips FDA to act quickly, limit the spread of New World Screwworm, and protect America’s livestock.”

Currently, there are no FDA-approved drugs for NWS in the U.S. The FDA through an EUA can authorize the flexible, faster use of certain animal drug products that may be approved for other purposes, or available in other countries, but not formally approved for NWS in the U.S. This ensures veterinarians farmers, and animal health officials have timely access to the tools they need to protect pets, livestock, and the nation’s food supply, according to an HHS release.

Editor’s note: Sara Wyant is publisher of Agri-Pulse Communications, Inc., www.Agri-Pulse.com.