Missouri Response to New World Screwworm Detection in U.S.

(JEFFERSON CITY, Mo.) – The United States Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS) has confirmed the presence of New World Screwworm (NWS) in the United States. On June 3, 2026, USDA confirmed NWS in a 3-week-old calf in Zavala County, Texas.

NWS is a serious pest that affects livestock, pets, wildlife and less commonly, people and birds. NWS larvae burrow into the flesh of living animals, causing serious damage to livestock and economic losses to producers.

The Texas case is the first detection of NWS in the U.S. since northward progression from Central America was observed in 2023. In preparation for the potential re-emergence of NWS in the U.S., Missouri assembled a New World Screwworm joint working group. Led by State Veterinarian Steve Strubberg, the working group is comprised of representatives from USDA, Missouri Department of Agriculture, University of Missouri Extension, Missouri Department of Conservation and Missouri Department of Health and Senior Services.

The working group prepared a Missouri NWS Response Plan. In light of the U.S. detection, Missouri has activated the Response Plan.

Animal movement into Missouri

• Any warm-blooded animals traveling from an infested state, but not an infested zone, can enter Missouri with a Certificate of Veterinary Inspection (CVI) that includes a statement “All animals in shipment do not originate from or transit through a NWS Infested Zone.”
• Any warm-blooded animals that originates from an infested zone will need to meet the movement requirements for the state of origin and obtain a permit from the Missouri State Veterinarian’s office and have a CVI that states “all animals listed were individually inspected and found free of wounds.”

Steps to protect your animals

• Prepare.
  • Develop and implement strong fly and tick protocol for animals.
  • Clean, treat and cover open wounds.
  • If possible, delay practices which cause skin openings such as castration, dehorning or branding. Treat areas where these practices are performed.
  • Register your farm for a premises ID so the Missouri Department of Agriculture can notify you if NWS is confirmed in the state.
• Inspect.
  • Regularly monitor animals for signs of infection or maggots, especially around areas of castration, dehorning, branding, umbilical site, scrapes, lesions or a tick-feeding site.
  • Know the signs:
    • Bloody or light-colored drainage from a cut or wound.
    • A cut or wound that rapidly enlarges for seemingly no reason.
    • White or cream-colored runny substance (the eggs) in and around a wound.
    • Presence of fly larvae (maggots) in wounds.
    • Irritated behavior and signs of pain.
    • Head shaking.
    • Reduced appetite.
    • Fever and other signs of secondary infection.
    • Foul odor or smell of decay.
• Act.
  • If you see a live animal with signs of infestation, report it immediately.
  • For livestock and pets, contact your local veterinarian or the MDA Animal Health Department at (573) 751-3377.
  • For wildlife, contact the Missouri Department of Conservation at (573) 522-0142 or report it online.

It is important to note that this detection does not impact food safety and the U.S. food supply is safe.

For more information about the NWS, visit the Missouri New World Screwworm website.

For more information about the Missouri Department of Agriculture and its programs, visit the Department’s website.

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