Rickettsiosis in Japan

Area of Science:

• Medical Entomology
• Infectious Diseases
• Epidemiology

Background:

• Rickettsial diseases in Japan include Tsutsugamushi disease (scrub typhus), murine typhus, and spotted fever group diseases.
• Tsutsugamushi disease cases significantly increased from 1976 onwards, with a notable outbreak in 1984.
• Spotted fever group rickettsiosis was newly identified in Japan in 1984.

Purpose of the Study:

• To report the resurgence of Tsutsugamushi disease in Japan.
• To document the emergence of a new spotted fever group rickettsiosis in Japan.
• To investigate the epidemiology and causative agents of these rickettsial diseases.

Main Methods:

• Analysis of reported incidence data for Tsutsugamushi disease from 1982 to 1986.
• Identification of a new spotted fever group rickettsiosis in Tokushima and Kochi Prefectures.
• Isolation of causative rickettsiae from patient blood samples using cell culture.

Main Results:

• Yearly incidences of Tsutsugamushi disease showed a significant increase between 1982 and 1986 (538 to 971 cases).
• Over 45 sero-positive cases of spotted fever group rickettsiosis have been identified since 1984.
• Causative agents of the spotted fever group disease were successfully isolated from five patients.

Conclusions:

• The resurgence of Tsutsugamushi disease is likely linked to an increase in infected vector mite populations.
• A novel spotted fever group rickettsiosis has emerged in Japan, requiring further etiological investigation.
• Continued surveillance and research are crucial for understanding and managing rickettsial diseases in Japan.