Six New World Screwworm Cases Confirmed in U.S. Animals Since Early June

U.S. Department of Agriculture reported. The goat case was announced June 9 by Secretary of Agriculture Brooke Rollins during a press conference.

The first infestation since 1966 was identified in Zavala County, La Pryor, Texas. A second cow case was later confirmed in the same state. The screwworm likely entered from Mexico and Central America.

U.S. closed its border to Mexican cattle in 2024 after the parasite spread through the region, Derrell Peel, a livestock marketing specialist at Oklahoma State University, told ABC News. Officials are still investigating how a dog became infected and believe the animal may have contracted the parasite in Mexico.

The USDA declared the screwworm eradicated from the United States in 1966. A small outbreak was eliminated in the Florida Keys in 2017, mainly among endangered Key deer. Rollins said the screwworm is not a food safety issue and does not affect meat quality.

Dustin Pendell, a professor of agricultural economics at Kansas State University, said Americans can continue to feel confident about consuming beef safely. Ben Weinheimer, president and CEO of the Texas Cattle Feeders Association, described the parasite as very treatable if caught early. The USDA is using the sterile insect technique.

Millions of sterile flies have already been released in the affected area. State officials have established quarantine zones to limit spread. Construction of a new sterile fly production facility is underway at Moore Air Base in Texas.

Rollins said the facility is scheduled for completion by November 2027. Once finished, an estimated 500 million sterile flies will be released weekly from the new site and other facilities. Screwworm infestations begin when a female fly lays eggs on open wounds or other body parts of live warm-blooded animals.