1980 Volume 54 Issue 6 Pages 279-283
A number of patients in recent Shichito lever endemic in Miyake Island was relatively small and only one isolation of avirulent strain (Miyake strain) from a field rodent was succeed in nude mice. These facts might indicate that presence of virulent strain which could isolate in conventional mice was limited in nature. Four time seroepidemiological surveys of field rodentsstudies by indirect immunofluorescence in Miyake Island showed that antibody positive rate was increased rapidly from 0%(0/25) in January 1977 to 83.3%(15/18) in November 1978 (isolation ofRt was negative). Field rats, Rattus norvegicus (Rn) and Apodemus speciosus (Apo) which were primarily living outdoors, showed rapid increase and reached high seropositive (from 0% to 85.7% in Rn and from 66.7% to 100% in Apo). On the contrary, Rattus rattus (Rr) which was mainly livingindoors, showed slow raise seropositive rate (from 0% to 50%). In nature, life span and maintenance of antibody of field rodents were about 1 year. These facts might indicate that in Miyake Island, high percentage of field rodents got infection in the last 2 years and the infected Rt was an avirulent strain like Miyake strain which could grow only in nude mice.
