Texas has announced it would begin rolling out a new strategy to prevent the New World screwworm, a flesh-eating parasite carried by flies, from infiltrating farms near the southern border. “We are taking proactive steps to monitor, detect, and stop this parasite before it harms Texas agriculture. Cases of New World screwworm in humans are rare, but possible. Sterilizing flies is the most effective way to prevent the spread of New World screwworm. As more sterile screwworm flies are released, the population of fertile screwworms decreases until it eventually dies out, according to the Animal and Plant Health Inspection Service.