Protecting South Carolina from New World Screwworm

The New World screwworm (Cochliomyia hominivorax) is a parasitic blowfly whose larvae feed on the living tissue of warm-blooded animals. Unlike common maggots that consume dead tissue, NWS larvae invade healthy flesh, causing severe wounds, infection and—in untreated cases—death.

All warm-blooded animals can be affected, including livestock, pets, wildlife and, rarely, humans. The pest is reportable to federal and state authorities, meaning any suspected case must be promptly reported.

• The screwworm was widespread across the southern U.S. until the 1960s.
• After SIT was introduced, the pest was declared eradicated from the U.S. in 1966, with programs extended southward.
• The most recent U.S. outbreak occurred in the Florida Keys (2016–2017), affecting endangered Key deer and domestic animals. Hundreds of deer died before state and federal agencies launched an emergency SIT program, releasing 150 million sterile flies over several months. By March 2017, the outbreak was declared eradicated.
• Since then, continuous surveillance and sterile fly releases along the Panama–Colombia border have protected North America.

Watch for these warning signs in livestock, pets and wildlife:

• Maggots in or around wounds, nostrils, eyes, ears, mouth or umbilical cords of newborn animals
• Foul-smelling discharge from wounds
• Rapidly enlarging wounds that fail to heal
• Restlessness or rubbing at wounds
• Loss of appetite or reduced weight gain
• Lethargy and weakness as infestations progress
• Secondary infections or swelling around wound sites
• Behavioral changes such as isolation from the herd
• In severe cases, death from untreated infestations

• S.C. Department of Natural Resources
• USDA-APHIS Screwworm Program
• CDC Overview of Screwworm and Myiasis
• New World screwworm: Information for Veterinarians
• Animal Drugs for New World screwworm
• NCBA New World Screwworm Resources
• Fact sheet for producers, veterinarians and pet owners (PDF)
• Cochliomyia hominivorax