Seroprevalence and associated risk factors of leptospirosis in human and small mammals in the Rejang basin

Mohamed Nur Azim, Mazlan (2014) Seroprevalence and associated risk factors of leptospirosis in human and small mammals in the Rejang basin. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

Leptospirosis is an important zoonotic disease in the world. The wet and warm climate in the Southeast Asia region provides a favourable condition for leptospires to survive in the environment and pathogenic leptospires have frequently been isolated from Malaysian waters and soils. A study was conducted in the Rejang basin of Sarawak from June 2009 to June 2012 to determine the seroprevalence of leptospirosis in the population and small mammals. The Rejang basin was chosen because leptospirosis cases had been previously found there. For human samples, all 508 sera were tested with Panbio® ELISA for leptospira IgM and the positive cases will be further examined by microscopic agglutination test (MAT) using 20 serovars obtained from the Institute of Medical Research (IMR), Kuala Lumpur. The seroprevalence of leptospirosis in human in the study area is 37.4% (190/508). The presumptive infecting serovars found were djasiman (22.1%), shermani (13.2%) and pomona (7.9%). For small mammals, 241 were trapped during the study and species that were trapped were Sundamys muelleri with 100 individuals (41.5%) (100/241), followed by Callosciurus notatus with 46 individuals (19.1%) (46/241), and Rattus exulans with 45 individuals (18.7%) (45/241). All blood extracted from small mammal samples were tested by MAT and ninety-eight (98) of sera samples tested (40.7%) (98/241) were positive for the antibody against Leptospira sp. with predominant presumptive serovars comprising of autumnalis (26.3%), tarassovi (23.2%) and bataviae (15.2%). The median age of seropositive cases was 42 years, many of whom were reliant on collected rain water and nearby river (74.7%) as their main water supply. More than half (56.3%) of the positive cases reported of having fever within the last 2-4 weeks before samples collection. Almost sixty percent (59.5%) of the seropositive respondent are females, whom are mostly housewives or farmers. Serovars australis, autumnalis, bataviae, canicola, iv celledoni, copenhageni, hebdomadis, tarassovi, pyrogenes, icterohaemorraghiae, ballum, shermani and panama can be correlated to both seropositive human and small mammals. Based on the result, Rejang Basin had the highest leptospirosis prevalence among human population and differences serovars compared to previous studies done in Malaysia. Logistic regression was used to identify factors associated with the leptospirosis infection. Factors that have significant association with the presence of leptospiral antibodies based on univariate analysis were: Primary education (OR= 0.654; 95% CI= 0.414-1.033), Secondary education (OR= 0.363; 95% CI= 0.219-0.602), presence of symptoms (OR=1.582; 95% CI=1.041-2.404), age groups of 11-20 years (OR= 0.291; 95% CI= 0.095-0.889), 21-30 ), 41-50 years (OR=0.323; 95% CI=0.115-0.911), 51-60 years (OR= 0.396; 95% CI= 0.137-1.141), Sarikei division (OR=0.360; CI= 0.169- 0.766) and contact with animal (OR= 0.511; 95% CI= 0.279-0.937). Based on multivariate analysis, the respondents’ educational level, age group and history of contact with animals remain to be significant. The respondents whom were defined as having the probable infection at time of survey were 5.3 times more likely to be symptomatic. The result also suggested that leptospirosis cases in Rejang Basin were most likely due to exposure to leptospires in the environment, possibly originating from the animal carriers. Due to the high prevalence of leptospirosis in the study area, appropriate public health and control strategies targeting this population should be implemented.

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