Source tracking of human leptospirosis: serotyping and genotyping of Leptospira isolated from rodents in the epidemic area of Guizhou province, China

BACKGROUND: Sustained human leptospirosis as well as death cases has been reported in Qiandongnan Prefecture, Southeast of Guizhou, China, recently, but these human patients were only clinically diagnosed, and leptospires have never been isolated from patients in these epidemic regions, In order to track the source of infection and understand the etiologic characteristic of leptospirosis, we performed rodent carrier surveillance for leptospirosis in the epidemic area in 2011. The population distribution of rodents in the epidemic regions was revealed. RESULTS: Four strains of leptospire were isolated from Apodemus agrarius. Microscopic agglutination test (MAT) confirmed the four isolates belonged to leptospiral serogroup Icterohaemorrhagiae. Multilocus sequence typing (MLST) indicated that all the four strains were defined as sequence type 1(ST1), which is identical to the three strains isolated from Rattus tanezumi in Rongjiang County in 2007. Clustering analysis of the MLST data indicated that the local isolates exactly matched with reference strain of leptospiral serovar Lai strain 56601, which is consistent with anti-Leptospira antibody detection of patients using MAT. CONCLUSIONS: Apodemus agrarius may be the potentially important carrier of leptospirosis and the potential source of leptospiral infection in human, and serovar Lai maybe the epidemic serovar of Leptospira in the localities.