Declining trend of malaria in Car Nicobar Island, inhabited by the Nicobarese tribe: Plausible factors.

torically known to be endemic for malaria1. However, during the past few years, its prevalence has been declining in three districts of the union territory, viz. (i) Nicobar; (ii) South Andaman; and (iii) Middle & North Andaman (Table 1). This is due to the strengthening of vector control activities (indoor residual spraying, weekly application of larvicides, etc) by local malaria department. Various health campaigns focused on adopting preventive measures against mosquito bites (repellents and bednets), enhanced the disease awareness among the community and helped in the early treatment seeking behaviour. Among the three districts, disease prevalence was highest in the Nicobar. This district accounts for only 9% of the population of Andaman and Nicobar Islands (36,842/ 3,80,581 census 2011), but contributed to 76% of malaria cases as per Department of Health Services, Port Blair, Andaman and Nicobar Islands. Both Plasmodium vivax and P. falciparum malaria are reported, and 17% of total cases were due to the later. However, the disease prevalence was found to reduce drastically during the past few years. The annual parasite incidence (API) declined from 92.28 in 2009 to 10.36 in 2014 (Table 1). This drastic decline was due to better hygienic measures adopted by the Nicobarese tribal population, improved living conditions by the post-tsunami developmental activities of the Nicobar administration and also the control measures undertaken by the malaria department. Each district consists of three tehsils, and the tehsils of Nicobar district, viz. Car Nicobar, Nancowry and Great Nicobar, have diverse topographies. Car Nicobar tehsil is a plain land, while Nancowry is a hilly terrain with dense forest tracts, and Great Nicobar has an admixture of both terrains. Anopheles sundaicus (Diptera: Culicidae) has been reported to be the most predominant mosquito species transmitting Plasmodium causing malaria2. In-depth studies on the bioecology of An. sundaicus have been undertaken in creek and non-creek areas of Car Nicobar Island. J Vector Borne Dis 52, June 2015, pp. 178–181