Dengue Vectors in Lao Pdr

An ecological survey of dengue vector mosquitos was carried out in June 2000 in central Lao PDR. Two areas in Khammouane Province, Nongbok and Thakhek, were selected for the survey. Of the 7 mosquito species identified, Aedes aegypti was dominant in both study areas. The container index for Ae. aegypti in Nongbok was 51.8% and was significantly higher than that of Thakhek (40.2%); moreover, significant differences between the study areas were found with records to containers and to the conditions surrounding the houses. The key containers in Nongbok were water jars, whereas drums or small or discarded containers had the highest occurrence rate of Ae. aegypti in Thakhek. Mesocyclops aspericornis was found in large water jars and cement water tanks; no Aedes larvae were found at these sites. Strategy to control dengue vectors in the study areas was discussed. Correspondence: Yoshio Tsuda, Department of Medical Entomology, Institute of Tropical Medicine, Nagasaki University, Sakamoto 1-12-4, Nagasaki 8528523, Japan. INTRODUCTION Dengue and dengue hemorrhagic fever have become a serious threat to public health throughout Southeast Asia (Gubler, 1997). There have, however, been few studies of the ecology of dengue vector mosquitos in Lao PDR (Jennings et al, 1995). Since vector control is the most effective measure currently used to reduce transmission of the disease (Reiter and Gubler, 1997), more studies of the ecology of the dengue vector mosquitos, Aedes aegypti and Ae. albopictus, are needed in order to enhance the control strategy in Lao PDR. Although a system for reporting cases of dengue fever in Lao PDR has yet to be properly established, an outbreak of dengue fever was reported in Khammouane Province, central Lao PDR, in 1998. Two areas in this province were selected for the present study, and breeding sites and conditions surrounding houses were examined in each study area to clarify area differences in vectors in relation to the difference in environmental conditions. During the larval survey, the presence of other insects and microorganisms, especially copepods, was checked to make a list of natural enemies of mosquito larvae. MATERIALS AND METHODS