Strain Variation of Rickettsia Orientalis in the Complement Fixation Test.

It is well known that Tsutsugamushi disease or scrub typhus in Japan has been prevalent in a limited northern district of the country, but Japanese investigators were not aware that there was a different type of scrub typhus in other parts of Japan, although some sporadic cases had been reported in the foothills of Mt. Fuji (Sakita, 1934), and Kanagawa Prefecture (Fukuzumi et al., 1950), which however were not reconfirmed by other investigators before 1948 when an outbreak of this disease among American soldiers of the Occupation Forces during maneuvers in the foothills of Mt. Fuji proved its existence in a district other than the above-stated well-known endemic foci of the country (406 MGL, 1948). Shortly afterward, organisms belonging to the Rickettsia orientalis group were isolated by several Japanese investigators from patients, rodents and trombiculid mites in different parts of the country (Dept. Health, Tokyo, 1952, Kawamura et al., 1952, Kasahara et al, 1953, Kimura et al., 1953, Kitaoka et al., 1953 a, Kitaoka et al., 1953 b, Ogasawara et al., 1953). Thereafter, we Japanese investigators generally considered these newly discovered diseases to be a new type of scrub typhus differing from the well-known classic type of the disease. Then, in 1954, a study team on scrub typhus was organized by a number of Japanese investigators including the author, headed by the late Dr. Takeo Tamiya, and an epidemiological study on scrub typhus of both the types has been carried out by this team for several years. Through an epidemiological survey carried out by this team, a) a large number of field rodents trapped throughout Japan were found very often to harvor this organism, b) the vector mites of this rickettsia were disclosed to be consisting of a number of different species, occurring at various seasons, c) the severity of the patients' symptoms seemed to vary according to the locality (Tamiya, 1962). The author's work in this team was concentrated on the classification of strains from different sources from the standpoint of antigenicity or immunological relationships, because it seemed very desirable for us to determine whether or not any relation exsists between the serological type of strain and its sources (Shishido et al., 1961, Shishido et al., 1962a, Shishido, 1962). The present study deals with variation of Rickettsia orientalis in the complement fixation test and its relationship to the sources. As is well known a heterogeneity exsists