Detection and modelling of case clusters for urban leptospirosis

Abstract

Summaryobjective To analyse the epidemiological profile of 488 cases of leptospirosis in Rio de Janeiro, Brazil between 1997 and 2002, using a variety of methods of spatial epidemiology, to establish alert guidelines in general hospitals, which might be a tool to improve diagnosis and treatment of leptospirosis to reduce lethality rates.methods Scan statistics identified six space-time clusters, which comprised a range of 2 to 28 cases per cluster. Generalized linear mixed models were used to evaluate risk factors for a cluster case which incorporated individual characteristics and spatial information on environmental and climactic factors in a single model frame.results Cluster case events were associated with heavy rainfall (OR 3.71; 95% CI 1.83-7.51). The model did not identify socioeconomic or environmental covariates that significantly influence the risk of developing a cluster rather than non-cluster case.conclusion Clustering of leptospirosis in this urban setting appears to be due to transmission during heavy rainfall.keywords leptospirosis, urban epidemics, geographic information systems, spatial epidemiology, generalized linear mixed model

Multiplex PCR-based detection of Leptospira in environmental water samples obtained from a slum settlement

“…The high incidence of negative samples observed in our work may be due to the fact that temperature is a limiting factor in the survival of leptospires (Levett 2001, Bharti et al 2003. Also, it is well recognized that rainy weather plays a crucial role in the environmental dissemination of this pathogen from the urine of infected animals (Kupek et al 2000, Levett 2001, Vinetz 2001, Tassinari et al 2008). …”

Interactions between environment, wild animals and human leptospirosis

“…Large cities are particularly prone to flooding by the combination of large paved, compacted or roofed areas that are more impermeable than vegetated land and generate more run-off (23). Urban severe leptospirosis outbreaks occur annually in large Brazilian urban centers such as São Paulo, Rio de Janeiro, Salvador and Recife cities during heavy rain periods and are mostly associated with precarious living conditions (12,28,41). Moreover, the seroprevalence of leptospirosis is inversely proportional to education level (28).…”

Seroprevalence and seroincidence of Leptospira infection in dogs during a one-year period in an endemic urban area in Southern Brazil

“…Although dog ownership has been previously identifi ed as a risk factor for severe human leptospirosis (12) , evidence of human infection in a low-income community in Brazil was not associated with dog ownership (6) . The serogroups associated with human infection (6) (13) (14) also suggest that the role of dogs in human infection may be limited or non-existent (15) .…”

“…Although rats (Rattus norvegicus) are considered a worldwide reservoir and the main source of human infections, dogs may also play a role as pathogen reservoirs (3) (4) in the disease cycle (5) . In developing countries, disease outbreaks are related to climatic conditions and are favored by high temperatures and rainfall during specific periods of the year (6) . Lack of basic sanitation, poor housing conditions and limited access to education and health increase the risk of human infection in urban areas (7) (8) .…”