Physicochemical characteristics of habitats in relation to the density of container-breeding mosquitoes in Asom, India.

BACKGROUND & OBJECTIVES Container-breeding mosquitoes, especially Aedes spp are vectors of diseases such as dengue and chikungunya. The abundance of these disease vectors in an area depends on the availability of container habitats and their physicochemical characteristics. The species composition of container-breeding mosquitoes in Asom, India was studied and the larval density was correlated with the habitat characteristics. METHODS Natural and man-made water-holding containers in Sonitpur district of Asom were surveyed for the presence of mosquito larvae. The percent composition of container-breeding mosquitoes and container index were calculated. The physicochemical characteristics of breeding water such as pH, conductivity, salinity, total dissolved solids, turbidity and dissolved oxygen were measured. RESULTS Aedes albopictus (93.7%) was the predominant species in the container-breeding habitats whereas Culex quinquefasciatus (2.77%), Armigeres subalbatus (2.26%), Ae. aegypti (0.76%), Toxorhynchites sp (0.4%) and Lutzia sp (0.11%) were recorded in relatively low numbers. The larval density (mean ± SEmean) of the container breeding mosquitoes ranged from 4.4 ± 1.8 to 15.4 ± 8.2, while the container index ranged from 1.58 to 5.68%. The mean (± SEmean) pH, conductivity, salinity, total dissolved solids, turbidity, and dissolved oxygen of water in the container habitats were 7.15 ± 0.11; 396.1 ± 58.5 μS/cm; 0.24 ± 0.04 ppt; 207.1 ± 30.4 mg/l; 32.3 ± 5.1 NTU; and 1.42 ± 0.12% respectively. The mosquito larval density in the container habitats was having significant negative correlation with the conductivity of breeding water (r = - 0.89; p = 0.003). Salinity, total dissolved solids and turbidity of water in the habitats were negatively correlated, whereas pH and dissolved oxygen were positively correlated with the larval density. INTERPRETATION & CONCLUSION The studies indicated the predominance of Ae. albopictus in the container-breeding habitats and reiterated its importance as a potential vector of dengue and chikungunya in the region. The spread of Ae. aegypti, the principal vector of dengue, in the semi-urban areas probably through road transport is a matter of public health concern. The use of conductivity of breeding water as an index for the proliferation of container breeding mosquitoes in the region could be explored further.