An epidemiological comparative study on diagnosis of rodent leptospirosis in Mazandaran Province, northern Iran

Abstract

Objectives: Leptospirosis is a zoonosis caused by leptospires, in which transmission occurs through contact with contaminated biological fluids from infected animals. Rodents can act as a source of infection for humans and animals. The disease has a global distribution, mainly in humid, tropical and sub-tropical regions. The aim of this study was to compare culture assays, the microscopic agglutination test (MAT), polymerase chain reaction (PCR), and nested PCR (n-PCR), for the diagnosis of leptospirosis in rodents in Mazandaran Province, northern Iran.

Methods: One hundred fifty-one rodents were trapped alive at 10 locations, and their urine and kidney samples were collected and used for the isolation of live Leptospira. The infecting serovars were identified and the antibody titres were measured by MAT, using a panel of 20 strains of live Leptospira species as antigens. The presence of leptospiral DNA was evaluated in urine and kidney samples using PCR and n-PCR.

Results: No live leptospires were isolated from the kidney and urine samples of the rodents. Different detection rates of leptospirosis were observed with MAT (21.2%), PCR (11.3%), and n-PCR (3.3%). The dominant strain was Leptospira serjoehardjo (34.4%, p=0.28), although other serotypes were also found. The prevalence of positive leptospirosis tests in rodents was 15.9, 2.6, and 2.6% among Rattus norvegicus, R. rattus, and Apodemus sylvaticus, respectively.

Conclusions: Leptospirosis was prevalent in rodents in Mazandaran Province, northern Iran. MAT was able to detect leptospires more frequently than culture or PCR. The kidney was a more suitable site for identifying leptospiral DNA by n-PCR than urine. Culture was not found to be an appropriate technique for clinical diagnosis.

Keywords: Culture; Iran; Leptospira; Mazandaran; Microscopic agglutination test; Nested polymerase chain reaction; Rodent.

Figure 1.

Map of the study area and sampling locations in Mazandaran Province, northern Iran.

Figure 2.

Sample of polymerase chain reaction results using the F1R1 primer (1,021 base pairs). Columns M1 and M2, DNA ladder (100 base pairs); columns 1-4 and 6-8, positive samples; columns 5 and 9, negative samples; column 10, positive control; column 11, negative control.

Figure 3.

Sample of nested-polymerase chain reaction products using the F1R1 and F2R2 primers. Column M, DNA ladder (100 bp); columns 1-7, positive samples. bp, base pairs.