United States Deploys Sterile‑Male Fly Program to Eradicate New World Screwworm

In June 2026 a Texas calf was confirmed to have a New World screwworm infestation, marking the first U.S. case since the pest was eliminated in 1966. Since then 42 cases have been identified in domestic livestock—primarily cattle, sheep and goats—and in dogs across Texas and New Mexico, though no wildlife infections have been reported.

The USDA announced the NovoFly program, a genetically engineered process that produces only sterile male screwworm flies. Developed by USDA’s Agricultural Research Service in partnership with North Carolina State University, the flies carry a red fluorescent marker for easy tracking. Using the sterile‑insect technique, males are irradiated to render their sperm non‑viable, released from aircraft, and allowed to mate with wild females, which then lay eggs that cannot develop. The initiative aims to contain and eradicate the pest, echoing the successful eradication effort of the 1960s.

The New World screwworm (Cochliomyia hominivorax) is a parasitic blowfly whose larvae feed on living tissue, causing painful wounds and potential secondary infections in livestock, pets and, rarely, humans. Prompt detection, treatment and biosecurity measures by producers and veterinarians remain essential while the sterile‑fly program proceeds.