Seroprevalence of tularemia in wild bears and hares in Japan.

Tularemia is a zoonotic disease caused by Francisella tularensis. The distribution of the pathogen in Japan has not been studied well. In this study, seroprevalence of tularemia among wild black bears and hares in Japan was determined. Blood samples collected from 431 Japanese black bears (Ursus thibetanus japonicus) and 293 Japanese hares (Lepus brachurus) between 1998 and 2009 were examined for antibodies against F. tularensis by micro-agglutination test (MA) or enzyme-linked immunosorbent assay. By subsequent confirmatory tests using western blot (WB) and indirect immunofluorescence assay (IFA), eight sera from Japanese black bears were definitely shown to be seropositive. All of these eight bears were residents of the northeastern part of main-island of Japan, where human tularemia had been reported. On the other hand, no seropositive Japanese hares were found. These results suggest that Japanese black bears can serve as sentinel for tularemia surveillance and may help understand the distribution of F. tularensis throughout the country. This is the first report on detection of antibody to F. tularensis in black bears of Japan.