There are now 20 confirmed screwworm infections in the United States, according to the U.S. Department of Agriculture's Animal and Plant Health Inspection Service.

None of those cases are in the Rio Grande Valley. The most recent infections were found in the Hill Country and Big Bend area.

Cattle families in the Valley say they are now required to submit health certificates for their animals when attending livestock shows.

"Before the average health paper would last you 14 to 30 days depending on which show you're going to, but now some of these shows have required that the vet needs to check them seven days out," San Manuel resident Enrika Hinojosa said.

One upcoming show is in Brenham. It started on Wednesday and will have a vet onsite, according to the show's Facebook page.