Study on effect of quality of water in Anopheles mosquito breeding habitats and control of Anopheles mosquitoes using larvivorous fish and carnivorous copepods

Abstract

Malaria is one of the most important health problems worldwide transmitted by anopheline (Diptera: Culicidae) mosquitoes. Sri Lanka declared elimination of malaria depending on the absence of indigenous cases of malaria for the past three years There is a possible risk of spreading malaria from imported cases as the major and potential vectors of malaria are still present in many parts of the country. Therefore, understanding the effect of abiotic and biotic factors on biology and ecology of immature stages of malaria vectors and identifying effective larval control methods will be very important for controlling malaria vector mosquitoes. Therefore, this study was focused on monitoring of entomological and ecological factors affecting distribution and density of malaria vector mosquitoes in the Districts of Mannar and Trincomalee (PART 1) and identifying possible biological control agents for malaria vector mosquitoes in the District of Kandy (PART 2). In the PART 1 of the study, a total of 1 440 households in eight possible malaria sensitive (sentinel) sites in the Districts of Mannar and Trincomalee were recruited Monthly entomological surveillance was performed in all study sites for 16 months (April, 2013 to July 2015). Physico-chemical parameters and aquatic macro-invertebrates in anopheline breeding habitats were studied. A total of 19 280 anopheline mosquitoes belong to 13 species were collected from the eight sentinel sites in two districts by standard anopheline collecting techniques. Abundance of anopheline larvae showed significant positive correlation (p < 0.05) with physico-chemical parameters in breeding habitats such as, temperature, Dissolved Oxygen (DO), and turbidity. However pH, conductivity, Total Dissolved Solid (TDS), salinity and hardness did not correlate significantly (p > 0.05) with abundance of anopheline mosquito larvae. Air temperature, rainfall intensity and wind speed are critical meteorological factors for distribution and abundance of malaria vectors A total of 34 and 35 macro-invertebrates taxa were collected from anopheline mosquito breeding habitats in the Districts of Mannar and Trincomalee respectively Presence of anopheline mosquito larvae was not significantly correlated (p > 0.05) with the prevalence of aquatic macro-invertebrate predators of the Orders Decapoda, Coleoptera. Hemiptera or Odonata. In the PART 2 of the study, highest predatory efficacy was observed in two fish species, 0. niloticus and P. reticulate under the both laboratory and field conditions respectively A copepod species, M scrassus denoted the highest predatory efficacy under the both laboratory and field conditions. Knowledge on ecological and biological factors affecting distribution of malaria vector mosquitoes and biological control agents for controlling malaria vector mosquitoes will be important for controlling malaria transmission from imported cases to neighborhoods in the future.