Screwworm Infestation Spreads Beyond Texas Control Zone, Threatening U.S. Cattle Herd

The New World screwworm parasite has expanded its reach in Texas, with infections now confirmed in at least a dozen cases, including cattle and sheep, moving beyond the initial containment area. This outbreak adds urgency to efforts to control the deadly pest, which poses a significant threat to the U.S. cattle herd, already at a 75-year low due to drought and high production costs. The U.S. Department of Agriculture confirmed new cases in sheep in Sutton County and cattle in Tom Green County, approximately 200 miles from the first U.S. detection in South Texas. This brings the total number of infections to at least a dozen, with eight of those being cattle. Experts express concern about further spread, with one associate professor at North Carolina State University noting that the topic dominated discussions at the American Association of Veterinary Parasitologists’ annual meeting. The screwworm fly lays eggs in open wounds of warm-blooded animals, and its larvae can be fatal if left untreated. While the parasite does not affect food safety, its impact on the cattle industry could lead to movement restrictions, delaying herd rebuilding and potentially driving beef prices higher. Governor Abbott has launched an online course to certify additional inspectors to manage livestock movement and ensure safety. Current movement protocols require authorization for animals leaving affected areas and inspection of carcasses by the Texas Animal Health Commission. Ranchers are reportedly better positioned than in the 1970s when a similar outbreak affected 1.5 million cattle in Texas. However, the primary strategy for eradication, the release of sterile flies, faces a significant delay. A plant in Texas intended to ramp up sterile fly production is not expected to be fully operational until November 2027. Currently, only a facility in Panama is producing a fraction of the necessary sterile insects. Officials acknowledge the challenge of containment until the U.S. production increases, with one official stating eradication won’t be possible until hundreds of millions more sterile flies are available, but containment is achievable. The full extent of the spread before the U.S. facility is operational remains uncertain. Some economists predict it could take two to three years to curb the spread, depending on the number of screwworms already present and the effectiveness of sterile fly mating. The U.S. is expected to be handicapped in its sterile fly dispersal efforts for some time.