Spatial epidemiology of suspected clinical leptospirosis in Sri Lanka

Abstract

Leptospirosis is one of the most widespread zoonoses in the world. A large outbreak of suspected human leptospirosis began in Sri Lanka during 2008. This study investigated spatial variables associated with suspected leptospirosis risk during endemic and outbreak periods. Data were obtained for monthly numbers of reported cases of suspected clinical leptospirosis for 2005-2009 for all of Sri Lanka. Space-time scan statistics were combined with regression modelling to test associations during endemic and outbreak periods. The cross-correlation function was used to test association between rainfall and leptospirosis at four locations. During the endemic period (2005-2007), leptospirosis risk was positively associated with shorter average distance to rivers and with higher percentage of agriculture made up of farms <0·20 hectares. Temporal correlation analysis of suspected leptospirosis cases and rainfall revealed a 2-month lag in rainfall-case association during the baseline period. Outbreak locations in 2008 were characterized by shorter distance to rivers and higher population density. The analysis suggests the possibility of household transmission in densely populated semi-urban villages as a defining characteristic of the outbreak. The role of rainfall in the outbreak remains to be investigated, although analysis here suggests a more complex relationship than simple correlation.

Distribution of leptospirosis patients in Sri Lanka: a retrospective study

“…Furthermore, the study of Robertson, Nelson and Stephen revealed that high risk of LP was positively and significantly associated with shorter average distance to rivers or canals in 2011. 7 Further, according to the geographical distribution wet zone of SL is classified as low lands, up lands and high lands obviously. The water drainage from high lands to low lands is grater due to the gravity.…”

“…6 The risk for LP was significantly positively associated with shorter average distance to rivers or canals and also positively associated with the agricultural land extend cultivated by the farmers. 7 LP is spreading among specific occupational groups such as farmers, miners, abattoir, sewer workers and among persons with recreational activities [8,9] . According to the medical statistics in SL, a dramatic increase in the number of cases hospitalized for LP has been observed in the past 10 years.…”

Spatial epidemiology of leptospirosis in Sri Lanka

“…To the Editor Robertson and colleagues [1] analysed the spatial epidemiology of leptospirosis in Sri Lanka and showed a probable correlation between occurrence of leptospirosis and rainfall patterns in Sri Lanka. They also identified risk clusters for leptospirosis based on the spatial distribution of the reported cases.…”

“…To address the specific criticisms raised by Agampodi, the paper [1] which describes its aim to validate the leptospirosis case definition in Sri Lanka using the microscopic agglutination test (MAT), does not report variation in clinical practice as a limitation in that study. It is therefore not unusual that we would use its findings as supportive evidence for doing a geographical risk analysis based on surveillance data, despite our noted warnings about misdiagnosis and clinical uncertainties.…”

Influence of Topographic and Hydrographic Factors on the Spatial Distribution of Leptospirosis Disease in São Paulo County, Brazil: An Approach Using Geospatial Techniques and Gis Analysis

“…Multiple geographical factors contributing to the human contact with bacteria and disease vectors, like slope terrain, land use, distance from rivers, sanitation conditions and socioeconomic level of population (Barcelos; Sabroza 2001; Reis, 2008;Soares et al, 2010;Robertson et al, 2012;Raghavan et al, 2012;Gracie et al, 2014;Vega-Corredor;Opadeyi, 2014). Outbreaks of leptospirosis in Brazil are concentrated between OctoberMarch months.…”