Several studies in different parts of Germany confirm the presence of R. helvetica. In the federal state of Baden-Württemberg in south-western Germany, adjacent to Bavaria in the West, 13% of I. ricinus were found positive for R. helvetica (Hartelt et al. 2004), and in various public parks in Bavaria, an average of about 7% of the I. ricinus ticks carried R. helvetica (Schorn et al. 2011). In eastern Germany, 18.8% of adult I. ricinus were positive in Thuringia (Hildebrandt et al. 2010), in Saxony this percentage was 12.7% (Silaghi et al. 2011), while in Berlin only 14.2% of I. ricinus nymphs were reported positive (Pichon et al. 2006). Assuming that R. helvetica is the rickettsial species most frequently found in I. ricinus, this species would account for the majority of rickettsiae found in studies which do not distinguish between the species because a generic PCR (e.g. targeting the gltA gene, Wölfel et al. 2008) is used; the overall prevalence of R. helvetica is above 10%.

No detailed data on the seroprevalence rates of antibodies against R. helvetica in animals are available. In a study in Myodes (M.) glareolus and Apodemus (A.) flavicollis, only 1/110 transudates of M. glareolus and 0/98 transudates of A. flavicollis were found positive for R. helvetica antibodies, while 14/110 sera of M. glareolus and 11/98 transudates of A. flavicollis showed antibodies against R. conorii (Dobler and Wölfel 2009).

There is some evidence that larger game animals and larger farm animals may play a role for the transmission of R. helvetica. However, systematic studies are lacking. There is, however, good evidence that transovarial transmission may play a major role for the maintenance of R. helvetica in nature. In a study testing I. ricinus of different developmental stages from eastern Bavaria for R. helvetica, 7/136 unengorged tick larvae were found positive, implicating that the larvae had been infected via transovarial transmission.

Seroprevalence data of antibodies against R. helvetica in humans in Germany are missing so far. In a serosurvey in France, 9.2% of tested forest workers in the Alsace region were found positive for IgG against R. helvetica (Fournier et al. 2000). In a seroprevalence study in Poland, none of 129 analysed sera showed clear positive reactivity against R. helvetica (Podsiadly et al. 2011).

R. helvetica seems to play a minor role in human pathogenicity. An earlier report on its role in aetiology of myocarditis has not been confirmed so far (Nilsson et al 1999). However, it seems to play a role as cause of undifferentiated flu-like disease with fever and constitutional symptoms (“aneruptive fever”) during the time of activity of I. ricinus (Fournier et al. 2000). Rather recently, a case of meningitis was traced to R. helvetica in a patient in Sweden (Nilsson et al. 2010). Seroprevalence rates of 5–10% imply that infections of R. helvetica in humans may be more frequent than thought but that, in many cases, symptoms may be lacking or mild. There is no evidence that R. helvetica is causing animal disease.

While no data on the prevalence of R. monacensis in ticks of the original isolation are available, additional data on the detection of this rickettsial species in ticks in north-eastern Bavaria resulted in a prevalence of 0.55% (8/1,450) for R. monacensis in I. ricinus. In Thuringia, 12 out of 64 rickettsiae-positive I. ricinus of which the species could be determined (147 out of 1,000 tested I. ricinus were positive for Rickettsia spp.) were R. monacensis (Hildebrandt et al. 2010). The detection in this region constitutes the most northern detection of this rickettsial species so far. Rickettsia monacensis since then has been detected in additional European countries. A recent study found R. monacensis in Hungary with a prevalence rate of 0.9% (Sreter-Lancz et al. 2005). The area where R. monacensis had been detected is close to the former Czechoslovak Republic, where R. sp. IRS4/IRS3 was detected (Sekeyova et al. 2000). Further studies also detected R. monacensis or a very closely related strain in Bulgaria (Christova et al. 2003). Molecular studies comparing the two Bavarian strains of R. monacensis showed that R. monacensis is closely related or identical to R. sp. IRS4/IRS3 (Dobler et al. 2009). These results are supported by similar results from a Hungarian group (Sreter-Lancz et al. 2005). Further studies in humans and molecular comparisons of German and Spanish strains have to show whether R. monacensis could also exhibit pathogenicity in humans in Germany and to determine the genetic homogeneity or plasticity of this rickettsial species over its wide geographical range.

There are no data available on the seroprevalence rates of antibodies against R. monacensis in animals. In this context, it should be stated that antibodies within the spotted fever-group and the typhus-group rickettsiae are cross reacting, but there is currently no species-specific serological test available that would allow the allocation of a particular sero-reactivity to a particular Rickettsia species within any of the two groups. This in turn means that any seroprevalence data can only be judged as group-specific antibodies.

There is increasing evidence that R. monacensis is circulating within a transmission cycle of ticks of the genus Ixodes and reptiles, mainly lizards (de Sousa et al. 2010). This host preference may explain the relatively low prevalence rates in ticks which have been found so far. On the other hand, a higher prevalence would be expected in climatic warmer regions, for example, the Mediterranean countries, with a year-round activity and higher abundance of reptiles in comparison to our regions north of the Alps. Further data on transovarial or transstadial transmission are not available. It is also not clear to what extent Ixodes ticks serve as vectors and as reservoirs for R. monacensis.

No data on the seroprevalence of antibodies against R. monacensis are available.

More recently, R. monacensis was detected in the blood of two patients in Spain presenting with a non-pruritic macular rash. Both patients did not show any eschars but sought medical attention with a diagnosis of Mediterranean spotted fever (Jado et al. 2007). These two patients are the first patients with R. monacensis as etiologic agent and demonstrate the pathogenic potential of this rickettsial species. So far, however, no human cases with symptoms of spotted fever were described in the area where R. monacensis had been isolated in Germany. No data on the pathogenesis in animals are available.

Rickettsia massiliae or a closely related (according to the ompB gene) rickettsial species was detected in one I. ricinus tick in an eastern Bavarian district (Dobler et al. 2009). To our knowledge, this constitutes the first and so far only detection of R. massiliae at all in Germany and also in ticks of the species I. ricinus. The medical importance for humans could be demonstrated by isolation of this rickettsial species from a patient with a classical spotted fever in Parma, Italy (Vitale et al. 2006). In Argentina, a patient showed a severe form of spotted fever caused by R. massiliae (García-García et al. 2010). Ticks of the genus Rhipicephalus seem to constitute the main vector and possible reservoir of R. massiliae in the Mediterranean, in Africa and in parts of northern and southern America. Rh. sanguineus is a highly abundant ixodid tick species of the warmer climate zones worldwide. If this tick species indeed serves as the main vector, this would argue for an overlapping distribution of R. massiliae with the corresponding geographical range of Rh. sanguineus. Because of high infestation rates of dogs with this particular tick species in the Mediterranean and the large number of dogs that travel from there, Rh. sanguineus is frequently imported into yet non-endemic countries, for example, Germany. Travelling infested dogs thus might also be carrying R. massiliae into different parts of the world. Due to the non-existence of Rh. sanguineus in Germany, the detection of this rickettsial species in I. ricinus is somewhat surprising. However, a former detection in ticks (Rh. sanguineus) in the Tessin in Switzerland seems to make a distribution north of the Alps at least possible. Furthermore, Czech scientists recently also reported on the detection of rickettsial DNA closely related or identical to R. massiliae in I. ricinus in the Slovak Republic (Derdáková et al. 2011). These results imply that R. massiliae or a closely related Rickettsia species may be distributed in east-central and maybe central Europe. Further studies in ticks will have to show to what extent R. massiliae is circulating in Germany and whether it could be of importance as a human pathogen in the respective area.

Data on prevalence of rickettsiae in animal hosts other than ticks are not available. Also no information on seroprevalence of R. massiliae antibodies in animals is available.

No information on the transmission cycle of R. massiliae is yet available. It may, however, be speculated that dogs may play a potential role as vertebrate hosts as they may constitute important vertebrate hosts for the brown dog tick, Rh. sanguineus, which is the main vector of R. massiliae in the Mediterranean and in Africa. In Slovak Republic, R. massiliae was detected in ear biopsies of rodents. However, the potential role of rodents for R. massiliae has not been elucidated so far. As with the R. massiliae sequence detected in I. ricinus from eastern Bavaria, Rh. sanguineus is not present in Slovak Republic. Hence, another tick species than Rh. sanguineus, maybe I. ricinus, has to serve here as a vector and potentially also as reservoir.

Few population-based seroprevalence studies on antibodies against R. massiliae are available. In a study on patients with fever and symptoms compatible with spotted fever, a total of 15 patients from Catalonia, Spain, exclusively reacted against R. conorii and R. massiliae with significantly higher titres against R. massiliae than against R. conorii (Cardenosa et al. 2003). In a seroprevalence study in Polish forest workers, however, 15/129 (11.6%) sera reacted against R. massiliae (Podsiadly et al. 2011). These results and the detection of R. massiliae as cause in hitherto presumably diagnosed Mediterranean spotted fever cases imply that R. massiliae might be responsible for a part of those cases in the Mediterranean and possibly in other areas in the world.

Rickettsia massiliae may cause a severe form of spotted fever in humans, including fever, eschar, a maculopapular rash including palms and soles and a mild hepatomegaly. The clinical syndrome cannot be clinically differentiated from classical Mediterranean spotted fever. The incidence of infections with R. massiliae in humans is not known so far, but results in clinical studies show that it may be frequent at least in some areas around the Mediterranean. An important difference to other rickettsial species is the natural resistance against rifampicin (Rolain et al. 1998). This might be of importance as rifampicin constitutes an important antibiotic in the treatment of rickettsioses in childhood.