Dynamics of malaria transmission under changing ecological scenario in and around Nanak Matta Dam, Uttaranchal, India.

To understand the transmission dynamics of malaria in three different ecotypes, namely watershed (forest), seepage (Nanak Matta Dam) and plain (non-forest, non-dam) areas of Nainital and Udham Singh Nagar districts of Uttaranchal, entomological and parasitological investigations were carried out from July 1996 to June 1997. In the three ecotypes, average per man hour densities of adult vector species in human dwellings and cattlesheds recorded were high for Anopheles culicifacies from April to September and October to March for An. fluviatilis. Prevalence of both An. culicifacies and An. fluviatilis was higher in the forest area as compared to other two areas. Observations on gonotrophic condition revealed endophilic tendency of both vector species. Higher number of both vector species were found in outdoor than indoor during night human bait collections. Out of 864 specimens of An. fluviatilis dissected, one showed natural infection of sporozoites in salivary glands in the month of November from the forest area only. Sibling species study of An. fluviatilis revealed the presence of species S for the first time in the forest area. Parasitological investigations also depicted high incidence of malaria in the forest area as compared to other two areas. Overall results from the study indicated active malaria transmission in the forest area.