New World Screwworm

On June 3, 2026, the U.S. Department of Agriculture confirmed New World Screwworm in the umbilical area of a calf in Zavala County, Texas. This expansion into the United States is alarming and US Equestrian wants to make sure you know about the potential risks of this parasitic fly to horses. What is the risk of screwworm to horses? Screwworm myiasis (infestation) is caused by fly larvae (maggots) that feed on living tissue of any warmblooded animal. Horses, cattle, wildlife, pets, and...

On September 21, 2025, the United States Department of Agriculture announced the confirmation of a New World Screwworm (NWS) case in Nuevo Leon, Mexico, less than 70 miles from the U.S.-Mexico border. This new case is located near a major highway from Monterrey, Mexico to Laredo, Texas, one of the most heavily trafficked commercial thoroughfares in the world. Screwworm was once eradicated from the United States and potential incursion threatens the equine industry. Why is Protecting the United...