Geographical Spread of Anopheles stephensi, Vector of Urban Malaria, and Aedes aegypti, Vector of Dengue/DHF, in the Arabian Sea Islands of Lakshadweep, India

The Indian islands of Lakshadweep in the Arabian sea are known to be endemic for bancroftian filariasis. However, malaria endemicity was reported to be associated with the invasion of vector species Anopheles tessellatus from Maldives. Indigenous transmission of malaria was recorded during 1972. Thereafter the National Anti-Malaria Programme (NAMP) brought these islands under DDT spray. Since 1981, only imported cases of malaria are being reported from these islands. During March 2000, a brief survey of two islands, viz. Agatti and Kavaratti, revealed the presence of Anopheles stephensi, a known vector of urban malaria in the country. Earlier on the mainland, the southward peninsular spread of An. stephensi, including in Kerala, a non-malarious state, was recorded and the species was reported to be involved in two major outbreaks of malaria. It appears that over the years An. stephensi has invaded the Lakshadweep islands and gained a permanent foothold on these islands due to the availability of a large number of community and rain-harvesting cement storage tanks. These developments also threaten the northern islands of Maldives which are about 90 km south of Lakshadweep, where water storage practices are identical. Aedes aegypti which was earlier detected in the neighbouring group of Minicoy islands during 1974, has now spread widely in all the islands and poses an imminent threat of DF/DHF epidemics.