抄録
Until 1949, the epidemiological pattern of Izumi-fever was not clear and the disease had been presumed to be of streptococcal origin according to some clinical symptoms which are resembled to scarlet fever.
However, S. Kasahara (1949) who investigated the 1949 outbreak in Utsunomiya City, etiologically, clinically and epidemiologically, reported that this was a new viral disease in entity different from scarlet fever. And also, on the epidemiological grounds, he (1949) postulated “the rat reservoir theory” that rats may serve as a reservoir of this disease, and that the rats may probably convey infection by scattering their infected urine or excrements on the drinking water or the food. Indeed, he and his co-workers (1949) isolated the some strains of Izumi-fever virus from patients as well as from the organs, urine and feces of rat trapped in the epidemic area of Utsunomiya City.
Present report is to show the experimental proof of Kasahara's “the rat reservoir theory” as follows:
1) Seventeen strains of Izumi-fever virus were isolated by inoculating into rats, mice and guinea-pigs with pooled emulsion of liver, spleen and kidneys, and urine of 39 house rats (Rattus norvegicus and Rattus alexandrinus) trapped in eleven epidemic areas of Izumi-fever outbreak which was brought about from 1950 to 1954.
2) Histopathological changes of the caught rats, from which Izumi-fever viruses were isolated, proved the same characters ast hose of the animals infected experimentally with Izumi-fever virus, that is, the desquamation of tubular epithelial cells and the tubular casts in kidneys and so on. It is noteworthy that these house rats were trapped during epidemical period or after a lapse of 4 weeks, 12 weeks and one year since each outbreak.
3) The experimentally infected albino rats revealed an inapparent infection, and it was observed that they maintained the virus in their liver, spleen and kidneys for so long as 10 months after intraperitoneal inoculation.
