Distribution of Anopheles in Vietnam, with particular attention to malaria vectors of the Anopheles minimus complex

Background: The distribution of anopheline mosquitoes in Vietnam was examined, with a particular interest for the two sibling species of the Anopheles minimus complex ( Cellia: Myzomyia), An. minimus and Anopheles harrisoni, respectively former species A and C. Because the morphological identification of both sibling species is difficult and may lead to misidentifications, accurate data on their respective distribution are missing. This is of fundamental importance since the two species seem to exhibit differential vectorial capacities for malaria transmission. Methods: Large entomological surveys based on cattle collections and molecular identifications of An. minimus s.l. were carried out in 23 sites throughout northern, central and south-eastern regions of Vietnam. Results: Based on previous molecular works and our data, the distribution of anopheline species and the relative densities of An. minimus and An. harrisoni were mapped. It is noteworthy that there was a high specific biodiversity at each study site. Anopheles minimus s.l. and Anopheles sinensis were the main anopheline species in the northern region, whereas Anopheles aconitus and Anopheles vagus were the most frequent ones in the central region. The southern limit of An. harrisoni was increased to the latitude of 11 degrees N. Sympatry between both sibling species has been extended to new provinces. Conclusion: Malaria transmission is still high in central Vietnam and along bordering countries. Therefore, it is important to know and map the precise distribution of the main and secondary malaria vectors in Vietnam for applying efficient vector control programmes. Moreover, these maps should be regularly updated and linked to environmental characteristics relative to disease epidemiology, and environmental and climatic changes occurring in southeast Asia.