Abundance and distribution of Anopheles mosquitoes in a malaria endemic area along the Thai-Lao border.

Abstract

Malaria is an important public health problem in Thailand, especially along international borders. In this study, we conducted a longitudinal entomological survey in six villages and rubber plantation sites to address the spatio-temporal abundance and behavior of malaria vectorsin Ubon Ratchathani Provincealong the Thailand-Laosborder. Adult female mosquitoes were collected by human landing collections (indoor and outdoor) and by cattle bait collections twice per year, during rainy and dry seasons. Mosquitoes were morphologically identified and sibling species were determined byallele-specific PCR. Of the 10,024Anopheles, 9,328 (93.1%) and 696 (6.9%) were collected duringtherainy and dry seasons, respectively. A total of 9,769 (97.5%) and 255 (2.5%) was collected on cattle and human baits, respectively. Very few primary and secondary malaria vectors were collected, consisting of 12 specimens of An. dirus, eight An. minimus, and seven An. aconitus. Of the 152 specimens of the Maculatus Group, only three were identified to An sawadwongporni by molecular methods. The others were 112 An. rampae, a non-vector, that were not amplified or were misidentified as other non-vectors. Theverylow density of primary malaria vectors found in the study villages suggeststhat entomological risk and malaria transmission is higher in neighboring forest areas. Further studies on malaria vector distribution, as well as human behaviors, are needed to understand malaria transmission dynamics intheprovince and to develop suitable vector control methods.