Serosurvey for spotted fever group rickettsial infection in vertebrates in Shimane Prefecture

Abstract

We carried out a survey for the prevalence of antibodies to the spotted fever group (SFG) rickettsia in vertebrates such as dogs, cattle, deer, and mice in Shimane Prefecture. Rickettsia japonica was employed as antigen in indirect immunofluorescence (IF) tests. The experiment for natural infections using decoy animals was performed in the field of the endemic area. 1. Among 115 street dogs, 18.3% possessed the antibodies against SFG rickettsia, while all of the 8 hunting dogs had the antibodies. 2. Among 234 cattle tested, 17.9% possessed the antibodies. IF titers were 1:40 to 1:160 (mean 1:68). 3. Among 69 wild deer, 92.7% possessed the antibodies ranging between 1:40 and 1:640, which showed the highest IF titers (mean 1:89) among those of the examined vertebrates. 4. The incidence of the antibodies in Apodemus speciosus, Apodemus argenteus and Eothenomys smithi smithi mice were 16.5, 4.3 and 0%, respectively. The incidence of the antibodies against SFG rickettsia in mice captured in the endemic area was significantly higher (22.8%) than that in non-endemicarea (10.4%). Difference in the incidence of antibody-positive mice was also observed within the endemic area. Therefore, we concluded that the infection of mice was restricted to a limited area. 5. No significant rise in IF titers was observed in decoy animals that had been infested with ticks in the endemic area.