Entomological risk factors for the high incidence of dengue in the forest fringe areas of Kerala, India
Author(s): Deepthi G Nair, Nisha P Aravind and Abin Varghese
Abstract: Incidence of dengue in Kottayam district, Kerala commences with cases reported from forest fringe areas of Kanjirappally every year. An entomological investigation was carried out to study the relative abundance of dengue vector and to delineate their breeding habitats in the forest fringe areas of Kanjirappally taluk. Four villages (Erumeli, Mundakayam, Kootikal, Koruthode) located in the forest fringe areas of Kanjirappally taluk have been selected for the study. In each study area all the breeding sources in and around 24 households covering an area of about 0.5 Sq Km were surveyed and checked for vector breeding at fortnightly intervals from February 2021 to October 2021. Immatures were collected from positive breeding site and were brought to the laboratory for emergence and species identification. Larval indices were calculated using WHO methods. Ae albopictus was found to be the most prevalent and widely distributed vector species and the primary vector Ae. aegypti was not found during the household survey. The maximum Container index and Breteau index were found to be 71.45 and 51.90 during the month of June and July which shows a linear positive correlation with rainfall and significantly higher pupal index was found during the month of May (2.96). Peridomestic water storage containers and rubber plantation associated containers were the main breeding habitat observed which accounts 64.08% and 80.29% of pupal production during the dry and wet seasons respectively. Sylvan environment of rubber plantation together with favourable climatic conditions are the key factors for the prevalence of dengue vector in the forest fringe areas of Kerala.