By Jules Bernstein
The New World screwworm lays its eggs in open wounds and burrows into skin. While human infections are rare, the insect poses an existential threat to cattle farming and dairy production. And it has returned to the United States.
While the U.S. Department of Agriculture officially declared the parasite eradicated from the country in 1966, several notable outbreaks and incursions have occurred since then. One of those is happening now.
On Wednesday, the USDA confirmed a case in South Texas. It could decimate that state’s $15 billion cattle industry, and poses a similar threat to California, where dairy and cattle lead the agricultural economy. Here, UC Riverside entomologists answer some of the questions naturally arising from such a threat.
Amy Murillo (AM) is an associate professor of entomology and is principal investigator of a project funded by the California Department of Food and Agriculture to monitor the state for early signs of the fly’s return. She is collaborating on the project with Alec Gerry (AG), a UC Riverside veterinary entomology professor.
Q: In December 2025, the fly was detected within 70 miles of the Texas border. Now that it is definitely in Texas, what tools does the U.S. have to combat its spread?
AG: The USDA and California, as well as other border states, have been preparing for the possible reinvasion of screwworm for many months. The USDA has developed a robust screwworm response plan which is now being implemented in Texas.
Source : universityofcalifornia.edu