Regional Differences of Leptospirosis in Sri Lanka: Observations from a Flood-Associated Outbreak in 2011

Citation: Agampodi SB, Dahanayaka NJ, Bandaranayaka AK, Perera M, Priyankara S, et al. (2014) Regional Differences of Leptospirosis in Sri Lanka: Observations from a Flood-Associated Outbreak in 2011. PLoS Negl Trop Dis 8(1): e2626. doi:10.1371/journal.pntd.0002626
Published: January 16, 2014

LeptospirosisLeptospirosis is known to be an important cause of weather disaster-related infectious disease epidemics. In 2011, an outbreak of leptospirosis occurred in the relatively dry district of Anuradhapura, Sri Lanka where diagnosis was resisted by local practitioners because leptospirosis was not known in the area and the clinical presentation was considered atypical. To identify the causative Leptospira associated with this outbreak, we carried out a cross-sectional study. Consecutive clinically suspected cases in this district were studied during a two-and-a-half-month period. Of 96 clinically suspected cases, 32 (33.3%) were confirmed by qPCR, of which the etiological cause in 26 cases was identified using 16S rDNA sequencing to the species level. Median bacterial load was 4.1×102/mL (inter-quartile range 3.1–6.1×102/mL). In contrast to a 2008 Sri Lankan leptospirosis outbreak in the districts of Kegalle, Kandy, and Matale, in which a predominance of Leptospira interrogans serovars Lai and Geyaweera was found, most cases in the 2011 outbreak were caused by Leptospira kirschneri. Seven (21.9%) confirmed cases had acute renal failure; five (15.6%) had myocarditis; severe thrombocytopenia (<20,000/uL) was seen in five (15.6%) cases. This outbreak of leptospirosis in the relatively dry zone of Sri Lanka due primarily to L. kirschneri was characterized by markedly different clinical presentations and low leptospiremia. These observations and data demonstrate the public health relevance of molecular diagnostics in such settings, possibly related to the microgeographic variations of different Leptospira species, but of particular value to public health intervention in what appears to have been a regionally neglected tropical disease.

Author Summary
Leptospirosis outbreaks occur predictably in Sri Lanka after seasonal rains and flooding in the endemic wet zone. Molecular investigations with quantification of a post-flood leptospirosis outbreak in the non-endemic dry zone of Sri Lanka in 2011 suggest variation of biological, clinical, and molecular characteristics compared to previous reported leptospirosis outbreaks in the endemic areas, probably showing a micro-geographic variation of leptospirosis. This work demonstrates the direct clinical and public health relevance of modern molecular diagnostic technologies to identifying an endemic neglected tropical disease where previously not suspected, especially in the resource-poor setting.

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