Abstract
Initially less studied than Ae. aegypti, research on Ae. albopictus has increased since the early '90, when this species increasingly extended its range into temperate areas of the world. Now, all continents are concerned by the risk posed by this species, which can transmit important arboviruses such as dengue, Zika, chikungunya, West Nile and yellow fever. The workshop addressed recent advances regarding the biology of Ae. albopictus, as well as many current knowledge gaps, including the distribution of this species in Asia, its ecology, its adaptation to urban environments, the impact of climate change on its distribution, vector competence, resistance to insecticides, innovative control strategies and new surveillance methods. The workshop was formally opened by a speech of His Excellency Prof. Chheang RA, Minister of Health in Cambodia, who highlighted the need for translational knowledge from fundamental research to applied research to improve vector control and surveillance services. He also emphasized the importance of public health issues related to infectious diseases and arboviruses in Cambodia. Indeed, recent years have demonstrated that we are far from eliminating dengue outbreaks and other arboviruses transmitted by Ae. albopictus. Last year, Vietnam recorded the historically highest number of cases of dengue despite organized surveillance established since the 1990s. Unfortunately, this year seems to be heading toward a record number of dengue cases worldwide, particularly following the epidemics in Brazil and Argentina. The first session focused on recent knowledge of Ae. albopictus in Southeast Asia, featuring speakers from Cambodia, Laos, Korea, and China. Sébastien Boyer, from the Institut Pasteur du Cambodge, presented the distribution and bionomics of Ae. albopictus in Cambodia, as well as this species ability to colonize various environments in Cambodia, including villages, cities, metropolises, forests, orchards, and plantations. Only in rice fields, which are now heavily populated by Culex mosquitoes, Ae. albopictus larvae were not collected. However, Ae. albopictus is found near human dwellings, not far from rice fields. There is also a significant presence of Ae. albopictus in Phnom Penh, with the mosquito being distributed throughout the capital. Additionally, this species is capable of efficiently transmitting dengue and chikungunya viruses, as well as showing resistance to insecticides. Veasna Duong, a virologist at the Institut Pasteur du Cambodge, presented data on the vector competence of key mosquito species in Cambodia. He highlighted the ease with which these species transmit Zika, chikungunya, and dengue viruses, underscoring their critical role in arbovirus transmission dynamics. In Cambodia, all four dengue serotypes co-circulate, with one serotype becoming dominant each year. A pattern of serotype, genotype, and lineage replacement over time was observed, which may be associated with large outbreaks. He also demonstrated that replacing genotype or lineage often exhibits better fitness in mosquitoes. For example, DENV-1 lineage 5 replaced lineage 4 and was linked to a major outbreak in 2019. Similarly, the DENV-2 Cosmopolitan genotype replaced the Asia 1 genotype in 2019 and was the predominant DENV-2 genotype during a significant outbreak in 2023. Sébastien Marcombe, from Vector Control Consulting -South East Asia, presented data on Ae. albopictus in Laos. This species is found in various ecotypes throughout the year, with higher densities during the rainy season and a peak in activity in the late afternoon.