Food supply 'not at risk' after new Texas screwworm cases, USDA secretary says

The U.S. food supply is "not at risk" from the return of the flesh-eating screwworm ​parasite to Texas, U.S. Department of Agriculture Secretary Brooke Rollins said on Monday. 

"This is not a virus, it's not a disease, it's just a little pest, a larva that lands in a calf's wound, for example, and it can be treated," Rollins said in an interview on CNBC's "Squawk Box."

"We have boots on the ground … we'll be able to beat this back, but we're going to do everything we can, investing over a billion dollars to push this pest back into Mexico, then to eradicate, as we did about 50 years ago," she later added.

Her comments came shortly before the USDA confirmed two additional cases of screwworm in Texas — one in a calf in La Salle County and another in a dog in Andrews County — bringing the total cases to four. The agency said more information will be released on the new cases, but that early reports indicate that the dog was recently in Mexico.

The newest case in Zavala County, Texas, was detected on a ranch roughly 5 miles from the first positive case of screwworm in Texas, which the USDA confirmed on Wednesday. They are the first screwworm cases since the 1960s.

The New World screwworm is a parasitic fly whose larvae burrow into the flesh of living warm-blooded animals, causing painful wounds that can become life-threatening without treatment. The pest poses a risk to livestock, wildlife, pets and, in uncommon cases, people.

Screwworms do not infest meat, fruits, vegetables or other food products, according to the USDA. Still, the cases mark a troubling return of the parasite and raise questions about how to keep it from spreading further into the U.S., reviving a threat the country spent decades working to eliminate.

Texas agriculture officials, including Commissioner Sid Miller, have criticized the USDA for a slow response that failed to halt the New World screwworm from crossing the border. In response, Rollins said Miller's recent comments are "disturbing and disruptive and so harmful to what we're trying to achieve."

"He knows that we have been moving at Trump speed," Rollins said. 

She said the U.S. will lean on the same playbook it used starting in the late 1950s, part of which involves releasing sterile insects to suppress the pest's population. She said the U.S. is already dropping around 10 million sterile flies a week on the affected area, both from the air and the ground. 

"We've beaten it before, we've got to beat it again," Rollins said.