FSIS Updates Veterinary Drug Residue Surveillance in Response to New World Screwworm
In a constituent update published on July 31, the U.S. Department of Agriculture's Food Safety and Inspection Service (USDA-FSIS) announced that it is enhancing its veterinary drug residue surveillance program under the National Residue Program, in response to the New World screwworm (NWS) fly moving into the U.S.
FSIS is targeting increases in sampling and has updated its laboratory analysis methods in an effort to strengthen its ability to detect potential residues from veterinary drugs used to treat or prevent NWS in livestock. USDA's Animal and Plant Health Inspection Service (APHIS) confirmed the first positive detection of NWS in the U.S. on June 3, 2026. The pest was previously declared eradicated in the U.S. in 1966.
While NWS itself does not pose a food safety risk in edible meat or poultry products, as explained by USDA Under Secretary for Food Safety Mindy Brashears, Ph.D. in a video posted by USDA in mid-June, residues from veterinary drugs used to treat and prevent infestations of NWS are potential chemical hazards.
FDA's Center for Veterinary Medicine has issued conditional approvals and emergency use authorizations for several drugs in multiple species of livestock. Producers and veterinarians in affected and adjacent areas may increase the use of these drugs to protect and treat their livestock; however, adherence to specified withdrawal periods is necessary to prevent violative levels of drug residues in meat products.
FSIS already tests for a wide range of veterinary drug residues, including residues associated with several NWS drugs. On July 17, the agency announced updates to two of its residue analysis methods, CLG-MEGA1 and CLG-MRM3, to detect additional analytes associated with the newly approved or authorized drugs. Beginning on September 1, 2026, FSIS will also increase routine residue surveillance at livestock slaughter establishments in targeted geographic regions, as described in FSIS Notice 30-26.
Establishments are required to retain livestock carcasses and their parts pending test results, unless FSIS condemns the carcass or the establishment decides to discard it voluntarily.
The agency will continue to publish its findings on the FSIS website through National Residue Program quarterly reports. Establishments with questions can contact their inspector or submit a question through askFSIS, selecting "Sampling" as the inquiry type. The full Constituent Update can be read here.
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