Nguy cơ nhiễm sốt rét ở các sinh cảnh khác nhau tại tỉnh Ninh Thuận

Two entomological surveys were conducted in specific forested environment in Ninh Thuan province during period from July 2005 to July 2006 in three villages in Ma Noi commune and in five villages in Phuoc Binh commune in Ninh Thuan province, South Central Vietnam. Collections were made inside the village, at the plot near the slash and burn fields in the forest and in the forest fringe. Both main (An. Dirus, An. Minimus) and secondary (An. Aconitus, An. Maculatus) vectors were found in all three settings, but in different densities. All collected mosquito species were subjected to enzyme-linked immunosorbent assay (ELISA) to detect Plasmodium in the head-thoracic portion of individual mosquitoes after morphological identification. Plasmodium infected mosquitoes were only found in the forest and forest fringe. Malaria transmission in the forested malaria foci was spread over the entire night, from dusk to dawn but was most intense in the early evening as 9 of the 14 Pasmodium positive bites occurred before 21h. The annual entomological inoculation rate in the forest was 7.29 and in the forest fringe was 7.65 infective bites per person-year to which Anopheles dirus s.s. and Anopheles maulatus s.l contributed. The vector behaviour and spatio-temporal patterns of malaria transmission in Central Vietnam impose new challenges to eliminate malaria from specific forest foci and urge to focus not only on the known main vector species. Moreover effective tools to prevent malaria transmission in the early evening and in the early morning, when the treated bed net cannot be used, need to be developed.