Epidemiological and entomological aspects of an outbreak of chikungunya in Lakshadweep Islands, India, during 2007.

ABSTRACT

Since 2006, the Indian state of Kerala has reported outbreaks of chikungunya (CHIK). During July-August 2007, an unusual increase in the incidence of fever was noticed in Kadmat, Amini and Kavaratti Islands in the Union Territory of Lakshwadeep, a group of Indian islands adjacent to the Kerala coast inthe Arabian Sea.The populations affected as per the primary health centre (PHC) records of three islands, viz. Kadmat,Amini and Kavaratti, was 85%, 1.4% and 0.15% respectively. Entomological surveys revealed very highlarval indices of Aedes albopictus only in the three surveyed islands. Aedes aegypti, the classical vectorof dengue, was not detected. The maximum breeding of Ae. albopictus was found in coconut shells(57%), tyres (9%), metal containers (9%) and plastic containers (8%). The breeding was also detected intree holes and rat-bitten coconuts on top of the trees. The House Index for Ae. albopictus rangedbetween 95.4% in Kavaratti to 79% in Amini. Kadmat island which was the worst affected, recording the maximum Container Index of 90%, compared with 40% in Amini island. The CHIK outbreak seemed to have been caused by importation of the virus from Kerala, because of heavy movement of the islanders to the mainland.