Mapping of lymphatic filariasis in India.

The derivation of detailed epidemiological maps, at the relevant spatial resolution, is being increasingly recognized as vital to the effective design and implementation of successful programmes for the control of parasites and their vectors. Geographical information systems (GIS) and a recently complied database on the distribution of lymphatic filariasis in India have now been used to develop the first maps at district-level (i.e. the level at which control against this parasite will be enacted in India) of filariasis endemicity in this country. The derived maps indicate both the substantial extent as well as the marked variability in the geographical distribution of this disease in India. The causative infection and/or the symptomatic disease were detected in most (257) of the 289 districts surveyed up to 1995. Currently there may be up to 27.09 million microfilaraemics, 20.83 million cases of symptomatic filariasis, and about 429.32 million individuals potentially at risk of infection in the country. Probability mapping, based on data quantiles, clearly indicates that the risk of filarial infection in India is not constant throughout the country but exhibits strong regional trends. Filariasis in general may be a particular problem of the eastern half of the country. The results indicate the potentially vital role that GIS-based mapping approaches can play in the development of filariasis-control campaigns in India and elsewhere.