New World screwworm The U.S. Department of Agriculture has confirmed 12 cases of New World screwworm, or NWS, within the United States as of June 15. Confirmed detections include eight cattle cases, two goat herds and one sheep flock in Texas, and a dog in southeastern New Mexico. USDA, along with state animal health officials, continues surveillance, detection and mitigation efforts to limit further spread. The risk to California remains low. However, producers should remain informed and vigilant.