Seroprevalence of tularemia in rural Azerbaijan

A representative, two-stage probability sampling design was used to select 40 villages in northern Azerbaijan with populations of <500 people to screen for evidence of prior infection with Francisella tularensis. Informed consent was provided, and samples were obtained from 796 volunteers and tested for the presence of immunoglobulin G antibodies using enzyme-linked immunosorbent assay. F. tularensis seropositivity was prevalent (15.5% of volunteers), but there was minimal reporting of signs and symptoms consistent with clinical tularemia, suggesting that mild or asymptomatic infection commonly occurs. Frequently seeing rodents around the home was a risk factor for seropositivity (POR = 1.6, p = 0.03), controlling for age and gender. Geospatial analysis identified associations between village-level tularemia prevalence and suitable tick habitats, annual rainfall, precipitation in the driest quarter, and altitude. This study contributes to the growing understanding of the geographic distribution of tularemia and provides further information on the climatic and landscape conditions that increased the potential for exposure to this pathogen. The potential occurrence of asymptomatic or mild F. tularensis infection warrants further study.