The United States Department of Agriculture (USDA) has confirmed the first case of new world screwworm (NWS) in cattle in six decades, after the flesh-eating parasite was found in a calf in southern Texas, approximately 50 miles from the Mexican border. Agriculture Secretary Brooke Rollins announced the detection late on Wednesday, noting that the USDA and Texas officials had been warning livestock owners about the parasite's spread across Mexico for over a year.
The screwworm fly larvae feed on the blood of warm-blooded animals, posing a low risk to humans but capable of rapid spread among concentrated livestock populations. Eradicated from the US in the 1970s after causing tens of millions of dollars in losses, the parasite's resurgence now threatens an industry already facing record-high beef prices. While the flies do not affect food safety, officials fear potential shortages if they become established in cattle and poultry.
Texas Agriculture Commissioner Sid Miller criticised the USDA's response, stating that despite the release of billions of sterile flies, the screwworm has advanced over 1,100 miles from southern Mexico to Texas. He urged the Trump administration to deploy the screwworm adult suppression system (Swass), which uses attractants, bait, and targeted insecticides, alongside sterile fly releases. Rollins, however, defended her agency, asserting that there is no threat of mass infestation and that this is the only confirmed case in Texas since 1966.
The USDA has partnered with the army corps of engineers and a private company to build a new sterile fly production facility in Edinburg, Texas, to combat the spread. Female screwworm flies mate only once, and eggs from sterile partners do not hatch, reducing populations over time. Past eradication efforts were so successful that the US closed its sterile fly breeding facilities, leaving only one in Panama.
