MOLECULAR AND SEROLOGIC SURVEY OF ORIENTIA-TSUTSUGAMUSHI INFECTION AMONG FIELD RODENTS IN SOUTHERN CHOLLA PROVINCE, KOREA

Field rodents were collected from six areas in southern Cholla Provinc e, Korea from October to December 1993, Twenty-eight (24%) of the 119 Apodemus agrarius were seropositive (> 1:10) for Orientia tsutsugamush i by the passive hemagglutination assay (PHA). Of the seropositive cas es, 11 specimens had antibody titers greater than 1:80. No seropositiv e specimens were found among the eight Crocidura lasiura collected. On the other hand, the polymerase chain reaction (PCR) amplified about 5 20 basepairs of a gene encoding the 56-kD protein from the genomic DNA of 12 strains of O. tsutsugamushi tested. This target DNA sequence wa s amplified from the 11 (8.7%) blood specimens of A. agrarius, and one of the eight C. lasiura also showed evidence of O. tsutsugamushi infe ction by PCR. Only one of the PCR-positive samples was also PHA-positi ve. These results suggest that the PCR combined with a serologic assay more accurately detects the degree of infection of rodents with ricke ttsiae-causing scrub typhus in epidemiologic surveys.