Infection rate of Leptospira interrogans in the field rodent, Apodemus agrarius, in Korea

Leptospirosis has significantly decreased in Korea since 1988, following th e leptospiral vaccination programme initiated in 1988. Whether this wholly explains the decreased incidence is uncertain. As an initial step to answer this question, infection rates of Leptospira interrogans in field rodents, Apodemis agrarius, were examined and compared with previous data. Two hundred and twenty-two A. agrarius were captured during October-Decembe r 1996. Spirochaetes were isolated from 22 (9.9 %) and leptospiral DNA was detected in an additional 6 rodents (12.6 %). Subsequent microscopic agglut ination tests (MAT) classified all these isolates as L. interrogans serogro up Icterohaemorrhagiae serovar lai. The above data did not significantly di ffer from previous surveys in 1984-7. There was no significant change of L. interrogans infection in field rodents following the introduction of the v accination programme in Korea, Further studies are needed to determine the role of human vaccination in reducing incidence.