U.S. dairy farmers are collaborating closely with the U.S. Department of Agriculture (USDA), Food and Drug Administration (FDA), Centers for Disease Control and Prevention (CDC) and state veterinary and public health officials to safeguard dairy herds from New World screwworm.
New World screwworm myiasis (infestation) is not a food safety concern, but screwworm will have immediate interstate commerce and international trade effects for live animals.
New World screwworm flies are attracted to wounds. Animals that have recently given birth, suffered an injury, or had a surgical procedure (such as dehorning or branding) are most at risk. Untreated umbilical cords of newborn animals and foot lesions are commonly infested sites, as are tick bites.
Watch for symptoms:
Producers who suspect a screwworm infestation in one or more of their animals should immediately quarantine affected animals and report the case to their local veterinarian, State Animal Health Official or USDA. Do not attempt to treat suspected screwworm on your own without first reporting it to a veterinarian or health official.
When a screwworm infestation is identified in the United States, farmers can expect that animals will be subject to quarantine and movement restrictions.
USDA and/or state officials will immediately establish a minimum 20 km (about 12.5 miles) Infested Zone and a surrounding 20 km Adjacent Surveillance Zone around premises with an infested domestic animal, the location of infested wildlife, or the location of NWS fly detections. They will also establish a Fly Surveillance Area that overlaps and extends outward from the Infested and Adjacent Surveillance Zones.
Once an Infested Zone is established, officials will implement area quarantine and movement requirements, including pre-movement animal health inspection and treatment when appropriate, based on standardized continuity of business New World Screwworm animal health certification guidance.
If there is a suspected New World screwworm outbreak in your area, do what you can to prevent spreading:
An Emergency Use Authorization (EUA) is a temporary, emergency pathway that FDA may use after the HHS Secretary declares a public health emergency or significant potential emergency, as occurred for New World screwworm beginning in 2025. Extralabel use of FDA-approved animal drugs is limited to drugs with a new animal drug approval, which means it does not include conditional approvals or products with an emergency use authorization. A small number of animal drugs have full FDA approval for non-screwworm indications and conditional approval or an EUA for New World screwworm.
Animal Drugs for New World Screwworm >
Emergency Use Authorizations >
Talk to your veterinarian about treatment options. Typical livestock insecticide treatments may not contain a New World screwworm outbreak because of the difficulty in targeting wildlife for treatment. Past outbreaks have been controlled by sterilizing male flies, known as the sterile insect technique (SIT).
