Transmission dynamics & epidemiology of malaria in two tribal districts in Madhya Pradesh, India.

Malaria is a global health problem and India contributes substantially to the global burden of malaria1. About 60 per cent of malaria cases in India are confined to tribal areas2. Anopheles culicifacies and An. fluviatilis are efficient vectors in the tribal dominated areas. An. culicifacies is highly resistant to DDT3. Consequently, DDT was withdrawn from many tribal areas in 2001 and replaced by synthetic pyrethroid as indoor residual spray (IRS) (National Vector Borne Disease Control Programme, personal communication). Studies on impact of topography and ecological variations on the dynamics of malaria transmission are available only from a few tribal areas. In Mandla district of Madhya Pradesh (MP), density of An. fluviatilis was found to be relatively higher in forested villages than in deforested villages, resulting in variation in parasite rate and parasite proportion3. In Rourkela (Odisha), An. fluviatilis was absent in plain ecotype villages as compared to forest villages where species were prevalent with An. culicifacies resulting in significant variation in parasite rates in the two sets of tribal villages4. Similarly, in Koraput district (Odisha) marked variation in parasite rate was found between top hill and foot hill villages, and foot hill and plain villages of the two primary health centres (PHC). Within each PHC, both the hyperendemic and hypoendemic situations of malaria were recorded5. Thus ecological variations are known to have direct impact on vector prevalence and thereby malaria. Even in one topographic area distribution of vectors and malaria infection may not be homogeneous because of many factors6,7. Mandla and Dindori are highly malarious districts in MP, India, contributing together 12 per cent malaria in the State while their population is only 2.6 per cent of the StateState population. Bajag community health centre (CHC) in Dindori district contributs about 40 per cent malaria in the district though its population is 12 per cent of the district's population [State Vector Borne Disease Control Programme (SVBDCP), 2004, unpublished annual report]. In view of this, a study was undertaken to understand the site specific transmission dynamics of malaria to develop evidence based appropriate strategy for malaria control.