Livestock, News, Reuters U.S. not ready to lift Mexican cattle ban over screwworm, Agriculture Secretary Rollins says By Brendan O'Boyle, Cassandra Garrison, Reuters 6 hours ago The U.S. is not yet ready to reopen its border to Mexican cattle amid an outbreak of the flesh-eating New World screwworm parasite, Agriculture Secretary Brooke Rollins said, but she is pleased with Mexico’s efforts to contain the pest.