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New World screwworm: What you need to know

Confirmed cases of New World screwworm in the southern U.S. highlight the need for proactive monitoring, strong biosecurity, and rapid response to protect animal health.
Livestock Vet working in the barn with cows

What's happening now

Several confirmed cases of New World screwworm (NWS) have been identified in the United States near the Texas-Mexico border, following continued outbreak activity in Mexico. NWS can have severe impacts on animal health if not identified and treated quickly.

This situation underscores the importance of proactive monitoring, strong biosecurity practices, wound management, effective fly control, and close coordination with veterinarians and animal health authorities. Federal and state agencies are actively supporting containment efforts, including movement controls, surveillance, and sterile fly release programs.

Side view of a New World Screwworm fly

What is New World screwworm?

Side view of a New World Screwworm fly

New World screwworm is a parasitic fly whose larvae infest wounds in warm-blooded animals, including cattle, horses, and other species. If left untreated, infestations can lead to severe tissue damage, secondary infection, and, in serious cases, death.

Side view of a New World Screwworm fly

How MWI can support your operation

MWI Animal Health is actively monitoring the situation and providing resources to support customers in prevention and response efforts.

Products and preparedness

Access the supplies needed to support treatment and prevention, including wound care and fly control solutions.

2026 Livestock fly control guide

Strengthen your prevention strategy with our comprehensive guide.

Expert insights on New World screwworm

Close-up of two beef cattle

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Close-up of a horse's face in the sunlight

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Equine veterinarians’ vital role in identifying and containing New World screwworm

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Additional resources and official guidance

Information on New World screwworm continues to evolve. For the most up-to-date guidance, access the following resources.

USDA resources

Stop New World screwworm: Unified government response to protect the United States

Outbreak tracking and surveillance tools

Confirmed detections of New World screwworm