Human tularemia gained importance in Germany in the years after World War II [
2], a total of about 715 cases were notified from 1949–2008 [
14]. No systematic investigation on possible reservoirs of tularemia in endemic areas has been published for Germany so far. Public interest in tularemia increased in the last four years due to small localized outbreaks in the areas investigated in this study. Data on the prevalence of
F. tularensis in rodents as the suspected natural reservoir is of significant importance to German public health authorities in the endemic areas to provide a risk assessment for persons inhabiting or working in these areas.
Our study demonstrates that natural foci do exist in Germany with incidences of
F. tularensis in rodents of up to 10% in certain foci. The fact that no specific antibodies to
F. tularensis were found in any of the infected or uninfected animals argues in favour for the traditional view that
F. tularensis seems to be mainly fatal for infected rodents. However trapping indices in the investigations were good (e. g. in the DA investigation 65 animals/day using 200 traps) suggesting that a rather low prevalence may compensate the high lethality. The overall carrier rate of 4.92% is strikingly similar to the 4.76% found among different rodent species in a recently published study from endemic areas in China [
15]. Although the route of transmission to hares or humans still remains unclear,
F. tularensis seems to have a broad host range within small mammals. Because of the complete lack of seroprevalence found, none of them seem to represent a reservoir host for
F. tularensis. No tick or flea pool tested positive for the presence of
F. tularensis either. These findings are supported by the negative testing for
F. tularensis of more than 2,000 ticks (own unpublished data) over the last years from several areas of Germany, suggesting that neither ticks nor fleas seem to ingest
F. tularensis and thus are unlikely to be involved in its maintenance and transmission in Germany. These results are in strong contrast to other European countries like Slovakia or the Czech Republic where carrier rates of more than 10% were reported in ticks, mainly
Dermacentor reticulatus, in some endemic areas [
16]. This may be due to the fact that
Ixodes ricinus is the predominant tick in Germany and reports of
Dermacentor reticulatus are sparse (only 2126 between September 2004 and May 2006 in a nationwide study [
17]). Water on the other hand seems to be a possible route of infection, since we were able to find
F. tularensis DNA in a water sample for the first time in Germany. This is paralleled by studies from Scandinavia where water was found to be the source of
F. tularensis infections [
18].