Study on the Ecology of Anopheline Larvae in Malaria Endemic Areas of Tanowsri Canton, Suanphung District, Ratchaburi Province

Abstract

Abstract

The abundance of Anopheles larvae varies substantially among many hydrology-drivers ecological factors that directly effect vectorial competence. Larval habitats in the stream were identified in malaria endemic area. The distribution and abundance of Anopheles larvae were measured in relation to study variables of water such as dissolved oxygen, velocity, pH, temperature, COD, NO2, NH4, the width and depth of a stream, shade area of canopy vegetation and trees, sunlit area and amount of aquatic plant cover along a stream. Water samples were taken at 100-meter intervals, and were examined for the presence of anopheline larvae. Eleven Anopheles larvae species were identified in all the surveyed habitats. An. minimus was the most common species throughout the year (35.7%) and highest in February (22.4% of total An. minimus larvae). The relation between study variables of water and the abundance of two major species of malaria vectors (An. minimus and An. maculatus) and nine species of non-vectors (An. varuna, An. barbirostris, An. anularis, An. aconitus, An. kochi, An. vagus, An. hyrcanus, An. bengalensis and An. philippinensis) larvae was investigated. Regression analysis suggests that sunlit area cover along a stream and its width are the best predictor variables associated with the abundance of An. minimus larvae (p < 0.001); water temperature, amount of aquatic plant and shade area of canopy vegetation for An. maculatus larvae (p < 0.01); we could not identify key environmental variables for larvae of An. bengalensis, An. philippinensis and An. hyrcanus

Keywords: Anopheles larvae; larval habitats; ecological factors