Leptospirosis outbreak in Sri Lanka in 2008: lessons for assessing the global burden of disease

Abstract

Global leptospirosis disease burden estimates are hampered by the lack of scientifically sound data from countries with probable high endemicity and limited diagnostic capacities. We describe the seroepidemiologic and clinical characteristics of the leptospirosis outbreak in 2008 in Sri Lanka. Definitive/presumptive case definitions proposed by the World Health Organization Leptospirosis Epidemiology Reference Group were used for case confirmation. Of the 404 possible cases, 155 were confirmed to have leptospirosis. Highest titers of patient seum samples reacted with serovars Pyrogenes (28.7%), Hardjo (18.8%), Javanica (11.5%), and Hebdomadis (11.5%). Sequencing of the 16S ribosomal DNA gene identified six infections: five with Leptospira interrogans and one with L. weilli. In this patient population, acute renal failure was the main complication (14.8%), followed by myocarditis (7.1%) and heart failure (3.9%). The case-fatality rate was 1.3%. This report strengthens the urgent need for increasing laboratory diagnostic capabilities to determine the causes of epidemic and endemic infectious diseases in Sri Lanka, a finding relevant to other tropical regions.

Figure 1.

Selection of probable cases of leptospirosis, during the 2008 outbreak of leptospirosis in Kegalle, Kandy and Matale, Sri Lanka.

Figure 2.

Phylogenetic tree based on the Leptospira 16S ribosomal DNA gene. Sequences obtained in this study are indicated in sample numbers 334, 68, 109, 229, 75, and 82. Sequences were aligned in MEGA4 using CLUSTALW, and phylogenetic distances were calculated in MEGA4 using maximum-likelihood. Numbers at nodes are bootstrap support after 500 replicates.