Biting patterns and host preference of Anopheles epiroticus in Chang Island, Trat Province, eastern Thailand

A study of species diversity of Anopheles mosquitoes, biting patterns, and seasonal abundance of important mosquito vectors was conducted in two villages of Chang Island, Trat Province, in eastern Thailand, one located along the coast and the other in the low hills of the central interior of the island. Of 5,399 captured female anophelines, 70.25% belong to the subgenus Cellia and remaining specimens to the subgenus Anopheles. Five important putative malaria vectors were molecularly identified, including Anopheles epiroticus, Anopheles dirus, Anopheles sawadwongporni, Anopheles maculatus, and Anopheles minimus. Anopheles epiroticus was the most commonly collected species in the coastal site, whereas An. dirus was found to be most abundant in the forest-hill site. From both locations, a greater number of mosquitoes was collected during the dry season compared to the wet. Anopheles epiroticus showed greater exophagic and zoophilic behavior with the highest blood feeding densities occurring between 18:00 and 19:00. In contrast, An. dirus demonstrated an activity peak between midnight and 01:00. We conclude that An. epiroticus and An. dirus, in coastal and inland areas, respectively, appear to be the most epidemiologically important malaria vectors on Chang Island. As no studies of vector competency specific to Chang Island have been conducted, our conclusions that these two species play a primary role in malaria transmission are based on evidence from other localities in Thailand and mainland Southeast Asia. This information serves as a basis for designing improved vector control programs that target specific species, and if integrated with other interventions could result in the elimination of malaria transmission on the island.