Resources

As new information is released regarding the status of New World Screwworm, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), we will provide updates on this page.

 

View the most recent New World Screwworm outbreak map published by USDA.

 

21 November 2025 - USDA Launches new website: Screwworm.gov

The USDA has launched a centralized Screwworm website that it will use to organize and disseminate information related to this important pest. This website includes up-to-date distribution maps and information for stakeholders, the general public, veterinarians, and more.

 

22 September 2025 - USDA Confirms Screwworm in Northern Mexico.

New World Screwworms have continue to be detected further north in Mexico. The early July site in northcentral Veracruz (as shown on the map below) has been declared inactive, but cases have continued to spread in Oaxaca and southern Veracruz. The most recent announcement is of a confirmed case in Nuevo Leon, approximately 70 miles south of the US-Mexico border.

 

9 July 2025 - USDA Suspends the Import of Livestock from Mexico.

New World Screwworms have been detected further north in Mexico, resulting in the closure of Ports of Entry for livestock entering the U.S. from Mexico. The map below shows the current detection events of New World Screwworms in Central America and Mexico (as of July 9th, 2025), along with the US ports of entry that are suspended to livestock movement.

 

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USDA-APHIS New World Screwworm Current Status

When New World Screwworm larvae feed on and burrow into the flesh of a living animal, they cause serious, often deadly damage to the animal. This USDA page is updated frequently to track the current spread of NWS throughout Central and North America.

 

New World Screwworm Outbreak in Central America and Mexico

In 2023, New World Screwworm detections in Panama exploded from an average of 25 cases per year to more than 6,500 cases in 1 year. By November 2024, NWS had reached southern Mexico.

 

OSU Extension Pest E-Alert: Screwworm

The New World Screwworm is a parasitic pest once common in Oklahoma during warmer months, with seasonal migrations from southern states where it could survive the winter.

 

OSU Extension Experience Podcast: What is the New World Screwworm?

Dana Zook, OSU Extension Area Livestock Specialist, and Dr. Barry Whitworth, OSU Extension Area Food and Animal Quality Health Specialist, talk about the biology and historical impact of New World Screwworm.

 

CDC About New World Screwworm Myiasis

New World Screwworm infestation occurs when NWS fly larvae infest and feed on the tissue or flesh of warm-blooded animals, this is a condition known as myiasis.

 

History of the USDA New World Screwworm Eradication Program

Before its eradication from North and Central America, this caused devastating losses among livestock and wildlife. In the 1950s, USDA began using what is known as the Sterile Insect Technique (SIT) to eradicate this pest from the United States.