Protecting South Carolina from New World Screwworm
Current Situation
(As of Sept. 11, 2025)
No cases in South Carolina: NWS has not been detected in the state or anywhere in the U.S. at this time.
Outbreak in Mexico: As of Aug. 17, 2025, Mexico confirmed more than 5,000 animal infestations—a 53 percent increase since July. Most cases involve cattle but dogs, horses and sheep are also affected.
Human case: In August 2025, a Maryland resident who had traveled to El Salvador was diagnosed with NWS—the first confirmed human case in the United States in years. The patient recovered and no additional cases have been identified.
Risk level: Public health officials consider the risk to humans low but urge vigilance.
New World screwworm infestations begin when a female fly lays eggs on open wounds or other parts of the body in live, warm-blooded animals
Overview
Clemson University animal health experts are working with other state and federal agencies to keep South Carolina's livestock, pets and wildlife safe from the New World screwworm (NWS)—a dangerous parasitic fly that feeds on the living tissue of warm-blooded animals. While no cases have been reported in South Carolina, outbreaks are growing in nearby regions.
This site provides current information about NWS: what it is, how to recognize it, steps to prevent infestations and how to report suspicious cases.
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What Is 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.
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Resources & Links
- 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
New World screwworm is the larvae of the New World screwworm fly and feeds on the living flesh of warm-blooded animals.
