Historical Overview of Tsutsugamushi Disease in Japan before World War II.

Tsutsugamushi disease is a febrile mite-borne disease caused by Orientia tsutsugamushi. Before 1945, this disease had been prevalent in Niigata, Akita, and Yamagata prefectures for centuries, occurring in areas along major rivers in these prefectures every summer about a month after floods. The patients affected were farmers, possibly new settlers on reclaimed lands, who contracted the disease following bites of tiny red bugs. From the perspective of Western medicine, the disease was first identified by Nagino, Palm, Baelz, and Kawakami in 1878-79. In 1888, the Niigata Prefectural Government mandated the reporting of tsutsugamushi disease cases. In 1892, Tanaka associated the disease and eschars with mite bites. In 1917, Kitashima, Miyajima, and Okumura confirmed its transmission only by larval mites. Ishiwara and Ogata successfully maintained the bacteria in the laboratory through serial intratesticular passage in rabbits starting in 1927. In 1930-31, the causative organism was identified by Nagayo (Rickettsia orientalis), Ogata (R. tsutsugamushi), and Kawamura ("R. akamushi"). From 1932 onwards, the incidence of the disease began to decline slowly, possibly due to reduced human activity in riverside areas.