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Tick-transmitted spotted fever group Rickettsiae (SFGR) are considered emerging disease pathogens in Europe. To assess the situation in Germany, a seroepidemiologic survey of dogs ( n=605, which have never left Germany) was conducted to determine the prevalence of antibodies to SFGR. For this purpose, a commercially available enzyme-linked immunosorbent assay (ELISA) test for all SFGR was used. A total of 78% of the dogs were positive for antibodies of the SFGR, and there was a positive correlation between age, tick-infestation, and seropositivity. There was no correlation between clinical state, location, and seropositivity, suggesting that infection with rickettsia is neither related to the health condition of the dogs nor to their abode in Germany. According to our results, all of Germany can be considered as an endemic area for SFGR. This should be taken into account when assessing the epidemiology of human rickettsioses and their impact on public health. [ABSTRACT FROM AUTHOR]

Background: Spotted Fever Group (SFG) Rickettsiae can cause febrile diseases with or without rash in humans worldwide. In Germany only limited data are available about their medical significance. Serological screening tests for antibodies against rickettsiae usually only distinguish between SFG and Typhus Group (TG) Rickettsiae due to the strong cross reactivities within the groups. Seroprevalence rates in dogs, as possible sentinels for tick-borne diseases, could serve as an indicator for the distribution of different Rickettsia species. Methods: In this study, a micro-immunofluorescence assay (micro-IFA) was established for detection and differentiation of antibodies against five Rickettsia species in dogs (R. helvetica, R. raoultii, R. slovaca, R. monacensis and R. felis). Dogs that never left Germany (n = 605) previously investigated with an SFG-ELISA were included in this study and screened at a 1:128 dilution. Endpoint titres of fifty randomly selected seropositive samples of each of the five investigated regions in Germany were determined in order to allow a differentiation of the causative Rickettsia species. Sensitivity and specificity of the micro-IFA were compared with ELISA results of the previous study. Results: A total of 93.9% of the dogs were positive for antibodies of the SFG Rickettsiae at the screening titer of 1:128. Differentiation of SFG Rickettsiae with the micro-IFA was possible in 70.4%, but in 29.6% of the cases the detected antibodies were not differentiable. Considering a clear differentiation by a twofold titre difference between observed reactions, the seroprevalence rates were 66.0% for R. helvetica, 2.8% for R. raoultii, 1.6% for R. slovaca, but no serological reaction could be clearly attributed to R. monacensis or R. felis. No statistically significant regional differences were found for R. helvetica, R. slovaca and R. raoultii comparing the five regions of Germany. Comparison of micro-IFA with ELISA revealed a sensitivity of 82.0% and a specificity of 83.8% for the Rickettsia SFG ELISA. Conclusions: The micro-IFA is a useful serological tool to differentiate antibodies against different Rickettsia species in dogs. Seroprevalence rates in dogs correspond to the prevalence rates and distribution of Rickettsia-carrying tick species. [ABSTRACT FROM AUTHOR]