Calgary company steps up to help combat screwworm in U.S.

Calgary-based veterinary pharmaceutical company Solvet has received emergency use authorization from the U.S. Food and Drug Administration (FDA) to sell its equine ivermectin product in the United States. This product, formulated as a liquid solution, is specifically authorized for the short-term prevention of screwworm larvae in horses. According to Solvet CEO Lionel Gibbs, the product's aqueous base makes it highly concentrated and significantly easier to administer compared to traditional paste-based treatments.

Screwworm is a dangerous parasite; the female fly lays eggs in the open wounds of mammals, including livestock and occasionally humans. Once hatched, the larvae bore into the host's tissue, causing severe pain, secondary infections, and potentially death. The pest historically caused millions of dollars in losses for ranchers across Mexico and the United States until it was successfully eradicated from North America in 2006 using the sterile insect technique, which involves releasing mass quantities of sterilized male flies into the environment.

The parasite resurfaced in Central America and Mexico in 2024, gradually moving northward. In June 2026, the detection of screwworm larvae on a calf in Texas triggered a response from the Canadian Food Inspection Agency (CFIA), which prohibited the import of animals that had been in Texas within 21 days of entering Canada. This trade restriction highlights the severity of the threat currently facing the U.S. livestock industry.

In response to the FDA’s call for assistance to protect the food supply and producers, Solvet underwent a rigorous evaluation of its manufacturing facilities and product data. The resulting emergency authorization is narrow in scope: it permits the use of the liquid ivermectin for horses specifically for screwworm prevention. The FDA stipulates that the product must be administered within 24 hours of birth or at the time of initial wound care to effectively kill any larvae before they can cause significant damage to the animal.

John Gilleard, a veterinarian and parasitologist at the University of Calgary, noted that the authorization is a sensible step given the welfare risks associated with these parasites. He explained that early intervention in animals with open wounds is critical to preventing the tissue destruction typical of screwworm infections. While Solvet’s ivermectin product is used for a broader range of parasitic treatments in Canada, its deployment in the United States serves as a targeted emergency tool to manage the return of this flesh-eating pest.