New World Screwworm (NWS) is a fly, and the larvae of this fly burrow into living tissue of warm-blooded animals, causing large wounds and death in untreated animals.  The fly was eradicated from the United States in 1968, but an increase in cases in Central America in 2023 and 2024 has led to the discovery of the fly in Mexico.  USDA is working closely with Mexico to try to stop the spread of NWS before it can reach our southern border. If NWS is reintroduced to the United States, it could cost billions in treatment costs, production and death losses, and control measures.  It is critical for animal owners and veterinarians to be aware of the signs of NWS and to report any suspicious cases immediately to the State Veterinarian’s office.

Information:

• New World Screwworm Webinar
• Myiasis – Distinguishing NWS from Cuterebra (Botflies) 
• New World Screwworm ID Guide One Page
• Treatment of Wounds to Prevent New World Screwworm Infestation

Suspect New World Screwworm Links:

• Sampling kit order form
• New World Screwworm Suspect Submission Guidelines
• Utah Screwworm Suspect Report Form

Useful Links:

• USDA-APHIS Screwworm
• EPA List of Pesticides for NWS
• FDA Animal Drugs for New World Screwworm
• USDA Brochure
• National Cattlemen’s Beef Association Resources
• American Farm Bureau Federation
• Companion Animal Parasite Council
• USDA Accreditation module for veterinarians

USDA Response Plans:

• Animals
• Dogs

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