Widespread exposure to Francisella tularensis in Rangifer tarandus in Canada and Alaska

The range of tularemia, a disease caused by the bacterium Francisella tularensis, may expand alongside climate change in the North. Transmission occurs via biting arthropods, contaminated water sources, infected animal tissues and fluids and even aerosolized bacteria. Little research has been published on F. tularensis in northern Canada. We investigated whether Rangifer (caribou and reindeer) in Canada and Alaska are exposed to F. tularensis, as they provide significant cultural and subsistence value. From 2016 to 2020, 336 serum samples were collected from Rangifer across 17 herds, including captive reindeer in Alaska (n = 30) and wild caribou across Canada (n = 306) during collaring or harvesting efforts. Using a microagglutination test, we detected antibodies against F. tularensis in 7% of captive reindeer (CI₉₅ 2–21), 6% of migratory tundra caribou (CI₉₅ 4–11) and 10% of mountain woodland caribou (CI₉₅ 6–17), with the highest seroprevalence observed in animals from Nunavut (17%) and British Columbia, Canada (18%). Ten of the herds (n = 10/17; 59%) had at least one positive animal. Evidence of exposure to F. tularensis indicates that further studies are needed to characterize sources of transmission for Rangifer species and any potential health effects following infection.