Field rats form a major infection source of leptospirosis in and around Madurai, India

Aims: To determine the seroprevalence of leptospires and to isolate Leptospira spp. from field rats and bandicoots in and around Madurai. Materials and Methods: Thirteen rats and five bandicoots were trapped alive from fields in and around Madurai. Blood samples were tested for anti-leptospiral antibodies by microscopic agglutination test while the urine and kidney samples were used for isolation of leptospires. The isolated leptospires were tested for pathogenic status (13°C test and PCR) followed by serological and genetic characterization. Results: Serology revealed the presence of anti-leptospiral antibodies in 58% (7/12) of field rats and leptospires were isolated from two urine and six kidney samples. The bandicoots were negative in both serology and culture. Analysis of the isolates from field rats revealed that all the isolates were pathogenic except for one, which was further confirmed by serological and genetic characterization. Six of the seven pathogenic isolates were identified as L. interrogans serogroup Autumnalis serovar Akiyami A and one as L. borgpetersenii serogroup Javanica serovar Veldrat Batavia 46. Conclusions: Serology and isolation reveals that field rats are major natural carriers and shedders of leptospires in and around Madurai