Population Density of European Hare Predicts Risk of Tularemia Infection, Czech Republic, 2006-2022.

Background: Over 200 different animal species are susceptible to infection by tularemia, highly infectious disease caused by Francisella tularensis. Hares (Lepus sp.) and small rodents, such as common vole (Microtus arvalis), have been acknowledged as the most significant sources of human tularemia infection in most European countries. Our objective was to verify ability of these species in predicting incidence of human tularemia in a Central European country, the Czech Republic. Materials and Methods: We used 17 years of data on densities of European hare (Lepus europaeus) and common vole, and climate variability to test effects of these factors on temporal dynamics of tularemia incidence. The data were obtained from annual reports available from online e-repositories. Results: The analysis showed that 33% of the yearly variation in human tularemia incidence was explained solely by the abundance of European hare in the Czech Republic during 2007-2022. Density of common vole and North Atlantic Oscillation index, a measure of climate variability, did not significantly explain tularemia incidence. While hare population declined severely during 1993-2022, we did not detect any clear accompanied decrease in the prevalence of tularemia in humans and hares. Conclusion: Contrary to expectations, only hares proved capable in predicting yearly dynamics in human tularemia incidence in the Czech Republic. We call for continued monitoring of infection rates in hares and advocate the use of hunter estimates of hare abundance as a cheap and effective means of predicting the risk of tularemia.