16 NEBRASKA CATTLEMAN September 2025 PRODUCTION COMBATTING NEW WORLD SCREWWORM NATIONAL CATTLEMEN’S BEEF ASSOCIATION Nearly 60 years after New World screwworm (NWS) was eradicated from the United States, this pest is once again an animal health threat to American cattle producers. For months, National Cattlemen’s Beef Association (NCBA) has been collaborating closely with its state partners and the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) to protect the nation’s cow herd, but the situation remains far from resolved. Screwworm Status in the United States Currently, no cases have been detected in the United States. The northernmost cases in Mexico are roughly 370 miles south of the border. Mexico is dealing with roughly 3,800 cases total, mostly in cattle, but also some equines, dogs and humans. The outbreak in Mexico is a continuation of the spike in cases that began in Panama in 2023 and quickly spread through the rest of Central America. Screwworm was endemic in the United States from the 1930s to the 1960s. After decades of work by producers and APHIS, it was officially declared eradicated from the United States in 1966. In total, from the 1930s to the 1960s, the effort to eradicate screwworm in the United States cost more than $52 million. Adjusted to today’s value, that’s closer to $675 million. In 1996 (around the time sterile insect efforts began in Panama), screwworm eradication was estimated to save American producers $796 million per year. USDA’s Response USDA’s strategy to combat NWS centers on stopping its spread in Mexico, improving early detection of infected animals before they reach our border, strengthening U.S. disease response plans and treatment tools, boosting sterile fly production, and advancing research and producer education. USDA has also begun converting a facility at Moore Air Base in Texas so we can better disperse sterile flies in northern Mexico (and U.S. border states, if necessary). That facility will not produce sterile insects yet, so the flies will still be coming from Panama. Although all these steps are helpful, we urgently need a sterile fly production facility in the United States. NCBA’s Work NCBA has remained in constant contact with USDA-APHIS staff on this issue since cases started gaining momentum in Central America in October 2024, while educating and advocating on Capitol Hill. Securing $300 million to build or convert a U.S.-based sterile fly production facility remains a top priority. NCBA is actively pursuing every avenue to obtain this funding, so we have a sufficient supply of sterile flies to combat the pest. Treatment Options If NWS is suspected, a veterinarian should be consulted for treatment of affected animals. Currently, there are no animal drugs approved by the U.S. Food & Drug Administration (FDA) Center for Veterinary Medicine (CVM) for the treatment or prevention of NWS myiasis in animals. CVM is working with drug sponsors, federal and state partners and international regulators to understand options for U.S. veterinarians to treat NWS effectively and safely. Veterinarians may prescribe the use of FDA-approved products for uses that are not on the label, in accordance with the existing regulations with a valid veterinary/client/patient relationship. NCBA has also been working to reduce hurdles at USDA, EPA and FDA that Closeup of an adult New World screwworm fly. Photo by USDA.
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