Spatial analysis and privation index to identify urban areas with a high risk of lymphatic filariasis.

OBJECTIVE

To evaluate composite living conditions as indicators of urban areas with a higher risk of filariasis transmission.

METHODS

This was an ecological study in the municipality of Jaboatão dos Guararapes, in Brazil. The analysis units were census tracts. The study was divided into three phases. First, data gathered during an epidemiological investigation were analysed. Secondly, living condition indicators were drawn up and the relationship between these indicators and microfilaremia prevalence rates was analysed. Thirdly, positive cases were georeferenced with a view to identifying spatial concentration using kernel intensity estimates. Two composite living condition indicators were calculated: a socio-environmental risk index (in the form of scores) and a social deprivation index (through principal-component factor analysis).

RESULTS

Of 23,673 individuals examined, 1.4% had microfilaremia. According to the two indicators, greater prevalence was found in the high-risk strata, and this association was confirmed by the kernel intensity estimates.

CONCLUSIONS

Classification of census tracts into risk strata showed the relevance of socio-economic factors and environmental conditions in identifying priority areas in urban spaces for interventions by the surveillance services and in planning filariasis control. Spatial analysis also proved to be an important tool for building up a territorially based surveillance system. These indicators, used in association with spatial analysis, are an instrument to be used by the Global Programme to Eliminate Lymphatic Filariasis.