In a press release dated June 3, 2026, the USDA Animal and Plant Health Inspection Service confirmed detection of New World screwworm (NWS) in a 3-week-old calf located in Zavala County, Texas. This was the first confirmation since NWS was eradicated from the US in the 1960s, aside from a localized outbreak in Key deer in Florida in 2016-2017. Additional NWS detections have increased to six total domestic animal cases as of June 9, 2026, including four cattle, one goat and one dog case. The single case in a pet dog was identified in Lea County, New Mexico, on June 8, 2026, highlighting potential routes for further spread of the pest.
NWS does not pose a risk to food safety and USDA’s Food Safety and Inspection Service ensures the nation’s food supply is safe. After the re-emergence of NWS in Mexico in November 2024, the Swine Health Information Center has closely monitored NWS spread, hosted a webinar on the pest, and developed a new fact sheet for swine producers and other industry stakeholders.
Swine producers can prepare for NWS by understanding the fly’s behavior and life cycle, identifying production and housing conditions that increase the risk of myiasis, implementing effective biosecurity, environmental, and wound management practices, knowing the response procedures for suspected infestations, and developing an NWS disaster management plan. Monitoring for clinical signs of NWS in swine remains critical, including nonhealing wounds, wounds with a foul odor, biting or licking at wounds, depressed behavior, inappetence, and visible larvae in wounds. Any suspect cases of NWS should be reported immediately to state and/or federal animal health officials.
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