What to Know About the Screwworm Threat to US Livestock

The United States Department of Agriculture (USDA) confirmed an outbreak of New World screwworms in Florida on October 12, 2023, marking the first such occurrence in the continental U.S. since 1988. This parasitic insect infestation poses a significant threat to livestock, particularly cattle, as the larvae feed on living flesh. The USDA's Animal and Plant Health Inspection Service (APHIS) has been actively working to contain the outbreak, which was initially detected in a herd of 150 Key deer on Stock Island, Florida. Subsequent investigations identified infected cattle in Monroe County, Florida, leading to the implementation of control measures. These measures include the release of sterile male screwworms, a method that has proven effective in eradicating the pest in the past. The USDA has stated that this sterile insect technique involves releasing millions of sterilized flies, which then mate with wild females, preventing them from producing viable offspring and thus breaking the life cycle. The economic implications for the U.S. beef industry are considerable, as screwworm infestations can lead to severe animal suffering, reduced productivity, and potentially death, necessitating costly treatments and quarantine procedures. The USDA is urging livestock owners in affected areas to be vigilant and report any suspected cases immediately to prevent further spread.