Federal laboratories have confirmed two cases of the New World screwworm parasite in calves on a Texas ranch [4], [5].
The discovery of the flesh-eating parasite near the U.S.-Mexico border threatens the stability of cattle markets and risks a wider agricultural infestation [3].
Testing began on June 3, 2026 [1], when samples from calves at a ranch in La Pryor, Texas, were sent for analysis [1], [3]. The samples were processed at the National Veterinary Services Laboratories in Ames, Iowa [4]. While initial reports on June 3 described the infestation as unconfirmed [1], subsequent reports indicated a confirmed case in a calf [2].
By June 5, 2026, a second case of the parasite was confirmed [5]. The New World screwworm is a parasitic fly whose larvae burrow into the living flesh of mammals, causing severe tissue damage and potential death if left untreated.
Agricultural officials are monitoring the situation closely due to the location of the ranch in La Pryor, which is situated near the U.S.-Mexico border [3]. There are significant concerns that the parasite could spread from Mexico into the broader U.S. cattle population, which would disrupt trade and livestock management.
Government agencies have not yet released a full containment plan, but the confirmation of two cases marks a critical escalation from the initial testing phase. The rapid succession of confirmations between June 3 and June 5 suggests an active presence of the parasite in the local livestock population [1], [5].
“Two cases of the New World screwworm parasite in calves on a Texas ranch.”
The confirmation of screwworm in Texas represents a significant biosecurity threat. Because the parasite can devastate livestock populations and spread rapidly across borders, these cases may trigger stricter quarantine measures and impact the economic valuation of cattle in the region.
