Only one spotted fever rickettsiosis, Japanese spotted fever, caused by
R. japonica, has been described in Japan (
9). However, since 1993, 63 rickettsial isolates, which have been classified into six species on the basis of identical gene sequences or reactivities to MAbs, have been cultivated from six tick species (
4,
6,
20,
24,
25). In the work described here, we analyzed one isolate from each of these six rickettsial species. We identified isolates IP-1 and IM-1 as
R. helvetica strains, isolate IO-1 as being closely related to but different from
R. helvetica, and isolates FLA-1 and DT-1 as
R. japonica strains. In addition, we found that isolate AT-1 is a new genotype.
R. helvetica was first isolated in Switzerland from
I. ricinus, the vector of Lyme disease in Europe. Later, it was found in France, Portugal, and Sweden. In this work, it was isolated from
I. ovatus, the vector of
Borrelia japonica in Japan. Thirty-three strains were isolated from
I. ovatus ticks, two strains were isolated from
I. persulcatus ticks, and one strain was isolated from an
I. monospinosus tick; all of these strains belonged to the same serotype. At present,
R. helvetica is present only in
I. ricinus ticks in Europe, and our data show for the first time that the distribution of this bacterium is not limited to Europe but extends to Asia. As
I. persulcatus, the vector of Lyme disease in Japan (
21), belongs to the
I. ricinus complex, one could expect the area of distribution of
R. helvetica in Eurasia to be close to that of
Borrelia burgdorferi sensu lato. In Europe, forest workers in areas where
I. ricinus is prevalent have high seroprevalences of antibodies to
R. helvetica (
3). In Japan,
I. persulcatus tick bites have been reported (
7). Three patients reported similar fingernail-sized erythemas at the site of the tick bite. However, the role of
R. helvetica in this manifestation was not been demonstrated. Recently, another Japanese patient developed similar symptoms following an
I. persulcatus bite and seroconverted to positivity for antibodies to
R. helvetica (H. Inokuma and D. Raoult, unpublished data). At present, the pathogenic role of
R. helvetica has been demonstrated in two articles: in France, a man who had an isolated episode of fever and who had been exposed to
I. ricinus seroconverted to positivity for antibodies to
R. helvetica (
3), and in Sweden, two patients with sudden death suffered perimyocarditis caused by
R. helvetica, as determined by electron microscopy, PCR, and serology (
11).
R. japonica is the agent of Japanese spotted fever. In the present work, we confirm that
D. taiwanensis and
H. flava harbor isolates of
R. japonica. By using MAbs and PCR, this species was also identified in
I. ovatus ticks, which is discrepant with our results. We believe that
R. japonica may be present throughout the areas of distribution of
D. taiwanensis (eastern China and Taiwan) and
H. flava (Korea, China, and Taiwan). Very closely related organisms were reported in China (
26) and were isolated from
Dermacentor silvarum ticks (isolate 054, or “
Rickettsia heilongjiangii”) and
Haemaphysalis concinna ticks (isolate HL-93, or “
Rickettsia hulinii”). The spectrum of infected ticks is large, which is unusual for tick-transmitted rickettisae except
R. rickettsii (
14). It is also surprising that the geographical distribution of Japanese spotted fever is much more restricted than that of its vector tick. Usually, for SFG rickettsiae, ticks are both the reservoir and the vector of the bacteria (
14) and the geographical distribution of the disease is superposed on that of the tick. The notable exception to this is
R. conorii, which is absent in the Americas, despite the presence of
Rhipicephalus sanguineus, its reservoir tick (
13). As is the case for
R. japonica, the lack of evidence of Japanese spotted fever outside southern Japan may be caused either by a lack of infection or by the absence of recording of the disease.
We identified a new genotype in a rickettsial organism isolated from
A. testudinarium (isolate AT-1). This genotype is related to that for two rickettsiae previously identified in
I. ricinus ticks collected in Slovakia only by PCR amplification and sequencing (
18).
A. testudinarium ticks frequently bite humans in Japan (
9,
10) and could be a potent vector of rickettsial diseases. Recently, a case of pseudo-Lyme disease characterized by a skin lesion and local enlarged lymph nodes was observed in Belgium in a patient returning from Nepal. An
A. testudinarium tick was found on the skin lesion (P. Van Gompel, unpublished data). However, the causative role of AT-1 in this patient remains to be demonstrated.
In conclusion, we confirmed that the rickettsiae isolated from D. taiwanensis and H. flava ticks were R. japonica strains, and thus, these tick species are potential vectors of Japanese spotted fever. We identified R. helvetica outside Europe for the first time and identified a new genotype of rickettsia in A. testudinarium ticks. As the vector ticks easily bite humans, these rickettsiae represent a potential threat in Japan. Because the ticks analyzed are also prevalent in other areas of Central and Eastern Asia, the distributions of these rickettsiae may well be much larger.
This article has been 
9.