A three-week-old calf in Zavala County, southern Texas, has tested positive for the New World screwworm, marking the first detection of the deadly fly-borne parasite in U.S. livestock since 1966. The U.S. Department of Agriculture (USDA) confirmed the case, prompting immediate action from federal and state animal health officials. "A calf in southern Texas tested positive for the New World screwworm, the first instance of the deadly fly-borne parasite detected in U.S. livestock since 1966," reported The Wall Street Journal on social media.
The New World screwworm (Cochliomyia hominivorax) is an infamous parasite whose larvae infest open wounds of warm-blooded animals, feeding on living tissue and causing severe illness, and often death if left untreated. The United States successfully eradicated the screwworm in 1966 through a massive program primarily using the sterile insect technique (SIT). This historic achievement made the recent detection particularly alarming, highlighting the continuous threat of re-introduction.
Following the confirmation, USDA and Texas animal health officials have formed a unified response team and established a 12.5-mile (20km) infested zone around the detection site. Response measures include quarantine, strict livestock movement controls, enhanced surveillance, and expanded trapping efforts. Officials are also deploying ground-release chambers for sterile flies in the affected area, supplementing the 4 million sterile flies already aerially dispersed weekly.
The re-emergence poses significant economic risks to the livestock industry, with experts noting potential for increased treatment costs and market volatility. While the discovery has placed the industry on high alert, analysts and industry leaders urge calm, emphasizing that the situation remains manageable. "The most important thing for everybody to realize is that it is not hampering our food safety. There’s no risk to our food safety. This is not a disease," stated Tom Leffler, an industry expert.
Producers are advised to meticulously inspect livestock for enlarging or draining wounds, especially around newborn animals' navels, and to report any suspected cases promptly. While the parasite does not pose a food safety risk, its presence necessitates increased vigilance and management efforts from ranchers. The USDA continues to work towards limiting trade restrictions to defined geographic areas, with the primary goal of swiftly containing and eradicating the pest before widespread dissemination.
