抄録
There was an outbreak of about 30 cases of an acute febrile exanthematic disease among school children in Yamada, a mountain village in Toyama Prefecture, northern Honshu, during March-April, 1968. Laboratory tests for various exanthematic diseases were all negative, excepting for that positive results were obtained in Weil-Felix tests with OXK in 6 of 9 sera examined. Two out of 4 sera were a also positive in the fluorescent antibody tests against rickettsia of Tsutsugamushi disease. Seasonal surveys of trombiculid mites and tests of infection with the rickettsiae of the rodent hosts were carried out in the same area during one year's period from April 1969 at intervals of about one month. In the complement fixation tests of sera collected from 34 field mice (Apodemus speciosus) trapped during May and June, 17 (65%) were positive against Rickettsia orientalis. A total of 208 Apodemus speciosus and 15 Microtus montebelli were trapped and examined from the area during the one year survey, and altogether 7,504 chiggers (trombiculid mites) were recovered from these rodent hosts and from a wild bird Troglodytes troglodytes. The chiggers were classified into 5 genera and 10 species, as shown in Table 1. The most abundant among them was Leptotrombidium fuji, which showed peaks of the density both in autumn and spring. L. pallidum, a species known as one of the vectors of Tsutsugamushi disease in Japan, was the third in the order of abundance following Gahrliepia saduski, and also showed its peaks in the spring and autumn. Although further studies are necessary for drawing final conclusion, the above observations suggest that the disease could possibly be Tsutsugamushi disease transmitted to the patients by L. pallidum.
