Warble fly outbreak spreads across Mexico

In mid‑July 2026 the state of Chihuahua reported Mexico’s first confirmed case of the cattle warble fly (gusano barrenador) in a calf, prompting a sanitary containment protocol that established a 20‑km core zone and a 40‑km peripheral inspection area, treatment with ivermectin, and deployment of traps. Federal agencies (SENASICA, OIRSA, CPA) and U.S. authorities were brought in, and a large‑scale sterile‑fly release program was announced, aiming for millions of sterile flies weekly across the region. Within two weeks the parasite was detected in Durango, where a dog in the ejido La Mota, Muézquiz, suffered a severe botfly larval infestation. Authorities activated the same sanitary protocol, treated the animal, and began sampling. The Subsecretary of Agriculture reported the first positive dog cases in the urban area of Gómez Palacio and noted that Durango now had 48 active cases spanning equines, bovines and dogs. The spread prompted expanded surveillance, containment measures, and public advisories urging livestock producers and pet owners to inspect wounds and seek veterinary care promptly. By late July 2026 authorities in Chihuahua confirmed five additional cattle infections and 14 suspected cases, extending the sanitary fence to municipalities such as Parral, San Francisco del Oro, Allende, Coronado, Jiménez, La Cruz and Delicias. The sterile‑fly release program was intensified, using a 100‑million‑fly batch from the Panama plant and a new facility in Metapa de Domínguez, Chiapas, slated to scale up to 120 million flies weekly. Livestock owners received free treatments of doramectina, Exzolt and ivermectin while the 20‑km core and 40‑km peripheral zones remained in place. National reports indicated the parasite had been recorded in 29 states, with a cumulative total of 34,742 cases and 1,792 active infections (as of November 2024). States such as Aguascalientes and Coahuila reported active cases in cattle and a dog, prompting veterinary alerts.