Leptospirosis is one of the most widespread zoonoses and is caused by infection with pathogenic spirochetes of the Leptospira genus . Its incidence in humans is most frequent in developing countries, and the spectrum of human disease ranges from subclinical infection to severe symptoms of multiorgan disfunction with high case fatality rates, reaching mortalities as high as 70% in the case of severe pulmonary haemorrhage syndrome [2, 3]. There is, for certain, an underestimation of the leptospirosis problem due to a lack of awareness and under-recognition through a lack of proper use of diagnostic tools .
Leptospira are maintained in the genital tract and renal tubules of wild and domestic animals and are excreted with urine into the environment where they can survive for several months depending on favorable conditions such as warm, humid environment with a neutral to slightly alkaline pH [5, 6]. Rodents are recognized as important mammal reservoirs of Leptospira spp [7, 8], which only present mild chronic disease or are asymptomatic, and shed infectious organisms in the urine for their lifetime . Humans may be infected indirectly from animals by contact with contaminated water, soil or mud in a moist environment, or by direct contact with urine, fresh carcasses or organs . Therefore, surveillance on carrier status of reservoir hosts and analysis on the characteristic of causative agents contribute to the clinic laboratory diagnosis, active surveillance, outbreak investigation and source tracking for leptospirosis.
Sustained human leptospirosis as well as death cases has been reported in Qiandongnan Prefecture, such as Jinping, Liping, and Rongjiang County, Southeast of Guizhou, in recent years . According to the China National System for Disease Control and Prevention, twelve human leptospirosis cases with one death case were reported in Guizhou in 2011. However, Leptospira were never isolated from patients in recent years and the patients were only serologically diagnosed, and the etiologic characteristics of epidemic Leptospira remain unclear.
Traditionally, pathogenic Leptospira are classified into more than 200 serovars based on serological methods . Nowadays, multilocus sequence typing (MLST) method has been recently proved for typing leptospires [4, 13–15]. MLST is a simple PCR based technique, which makes use of automated DNA sequencers to assign and characterize the alleles present in different target genes. The selected loci are generally the housekeeping genes, which evolve very slowly over an evolutionary time-scale [4, 16] and hence qualify as highly robust markers of ancient and modern ancestry. The sequencing of multiple loci provides a balance between technical feasibility and resolution.
In order to track the source of infection and understand the etiologic characteristics of human leptospirosis in the epidemic area, we performed rodent carrier status surveillance in Jinping, Liping and Rongjiang County in 2011. Leptospiral isolates were serologically and molecularly identified and typed using MAT and MLST, respectively. Our results will contribute to the prevention and control of leptospirosis in the localities.