Studies on the Maintenance of 'Self-Sustained' Mosquito Vector Population in Vaigai River, South India

Study of mosquito species diversity and its relationship with ecosystems is essential to understand disease epidemiology and to develop control measures of vector populations in human-dominated ecosystems. In the present study, the structure and composition of immature mosquito population and associated ecological parameters were analysed in three different ecosystems (urban, semi-urban and rural) along Vaigai river, Madurai, Tamil Nadu, India. Average larval density was higher in urban than the semi-urban and rural sites during the study period. In 2012-13, immature mosquito diversity was higher in rural site during pre-monsoon and monsoon seasons, whereas mosquito larval diversity was greater in semi-urban site during the post-monsoon season. In 2013-14, mosquito larval diversity was found to be high in semi-urban site during monsoon and post-monsoon seasons. Culicine species dominated the urban areas, while Anopheline species dominated the rural and semi-urban sites during the study period. Among the mosquito species, Culex tritaeniorhynchus, Cx. geldius, Cx. vishnuvi, Cx. quinquefasciatus, Cx. bitaeniorhynchus, Anopheles subpictus and An. culicifacies were prevalent throughout the year. Filamentous algal-dominated sites showed a higher number of mosquito species (23 species) than other hydrophytes-dominated sites. Maximum number of sewage inlets was recorded in urban than the other two sites. As a result, the highest turbidity level was recorded in the urban site followed by semi-urban and rural sites. The present study shows that the immature mosquito population is maintained with the help of ecological parameters in all the study sites throughout the year. Therefore, it is essential to take steps to eradicate the mosquito vectors from the Vaigai river basin to avoid disease outbreak in the region.