Jpn. J. Infect. Dis., 59, 2006

Laboratory and Epidemiology Communications

Epidemiological Study of Japanese Spotted Fever andTsutsugamushi Disease in Shimane Prefecture, JapanKenji Tabara*, Ken Hoshina, Asao Itagaki, Takashi Katayama1, Hiromi Fujita2,
Teruki Kadosaka3, Yasuhiro Yano4, Nobuhiro Takada4 and Hiroki Kawabata5
Shimane Prefectural Institute of Public Health and Environmental Science, Shimane 690-0122;
Kanagawa Prefectural Institute of Public Health, Chigasaki 253-0087; 2Ohara Research Laboratory,Ohara General Hospital,Fukushima 960-0195; 3Aichi Medical University, Aichi 480-1195; 4University of Fukui,
Fukui 910-1193; and 5National Institute of Infectious Diseases, Tokyo 162-8640, Japan
1

Communicated by Ichiro Kurane(Accepted April 13, 2006)
Japanese spotted fever and tsutugamushi disease are tickborne infections that persist in Shimane Prefecture. Theirrespective causative agents are Rickettsia japonica andOrientia tsutsugamushi. We report here their outbreak characteristics.
Since the first report in 1987 (1), Japanese spotted feverhas been reported every year, totaling 80 cases at the endof 2005 (Fig. 1). Among 80 cases, it is estimated that 77
occurred in a mountainous area (ca. 10 km from east to west)of the Misen that is situated on the western end of the Shimane

Peninsula (ca. 60 km from east to west and 4 - 6 km fromsouth to north). More recently, however, the endemic area
has extended eastward; two cases occurred in the mountainous area 10 km east of the east end of the Misen, and one
case occurred at the eastern end of Mihonoseki-Cho, Matsue
City. The infection peaked in May in spring and from Augustto October in autumn (Fig. 2). Persistence of R. japonica in
the Shimane Peninsula was confirmed by its isolation frompatients and also by detecting an R. japonica-specific genesequence in Apodemus or Ixodes inhabiting the Shimane

Fig. 1. Yearly cases of Japanese spotted fever and tsutsugamushi disease in Shimane Prefecture, 1985 - 2005. □, Japanesespotted fever; ■, tsutsugamushi disease.

Fig. 2. Monthly cases of Japanese spotted fever and tsutsugamushi disease in Shimane Prefecture, 1985 - 2005. □, Japanesespotted fever; ■, tsutsugamushi disease.

*Corresponding author: Mailing address: Shimane Prefectural Institute of Public Health and Environmental Science, NishihamaSada cho 582-1, Matsue, Shimane 690-0122, Japan. E-mail:tabara-kenji@pref.shimane.lg.jp204

Peninsula (2,3).
Since 1985, 82 tsutsugamushi cases have been reported.
In 1998 - 2001, approximately 10 patients were reported regularly every year. More recently, the reported number dropped
to 2 - 4 cases a year, probably due to changes in the residentialenvironment. The infection has been most frequent in theeastern part of Shimane Prefecture and next most frequentin the central part of the prefecture, however, the westernpart of Shimane Peninsula and Oki Archipelago are not freeof tsutsugamushi cases. The infection has been high in
November to December in winter and in March to May inspring (Fig. 2). The serotypes of the human isolates wereGilliam type and Karp type. The Karp type O. tsutsugamushi
was isolated from Apodemus trapped in the endemic area.
Habitats of Leptotrombidium pallidum were confirmed in Oki
Archipelago and in the eastern and central parts of Shimane
Prefecture, but those of L. scutellare, a host of Kawasaki typeO. tsutsugamushi, were not. Probably, tsutsugamushi diseaseendemic to Shimane Prefecture is caused by Karp type andGilliam type O. tsutsugamushi transmitted by L. pallidum.

National Institute of Infectious Diseases, for advice on preparing the manuscript.
This article appeared in the Infectious Agents Surveillance
Report (IASR), vol. 27, p. 33-34, 2006 in Japanese.
REFERENCES
1. Oka, N., Kato, Y., Dekio, S., Nishio, T., Itagaki, A.,
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We thank Prof. Yoshikura, Emeritus Researcher of the205