Horizontal and vertical distribution of mosquitoes (Diptera: Culicidae) in the rainforest of Maromizaha, Madagascar: implications for pathogen transmission to humans and animals

The horizontal and vertical distribution of mosquito species was studied in Maromizaha rainforest, Madagascar. In November 2014, horizontal distribution was studied using light traps that were placed in four habitat types, ranging from degraded forest to primary rainforest. In November to December 2016, vertical distribution was studied using light traps placed near to the ground and elevated near the canopy. From the horizontal survey, 476 adults were collected: Uranotaenia (52.10%) and Culex (35.2%) were the most abundant genera. The highest numbers of mosquitoes were observed in the rainforest edge habitat, while the highest mosquito diversity was observed within primary rainforest. From the vertical survey, 276 adults were collected: Culex was the most abundant genus and represented 75.70% of adults caught. Mosquitoes were more abundant in traps placed near the ground than those near the canopy. The highest species diversity was observed near the canopy. The higher abundance of mosquitoes at the forest edge agrees with the role of this zone as an ecotone between intact rainforest and the nearest human habitation. Increased mosquito abundance in lower strata might heighten their contact with particular vertebrate hosts. The presence of vectors in different habitats and in varying elevations likely influences the risk of pathogen transmission between animals and humans in this rainforest.