Adaptation of Mosquito Vectors to Salinity and Its Impact on Mosquito-Borne Disease Transmission in the South and Southeast Asian Tropics

Abstract

Mosquito vector-borne diseases are a significant health problem in South and Southeast Asia. Some mosquito vectors in the region are well known to lay eggs and undergo pre-imaginal development in brackish water. However, a number of other important vectors, e.g. Anopheles culicifacies (malaria) and Aedes aegypti and Aedes albopictus (dengue and chikungunya), have previously been widely held to do so exclusively in freshwater. But recent evidence shows that these species can also lay eggs and undergo pre-imaginal development in brackish water collections in coastal areas of the region. This property produces a reservoir of vectors that are not targeted in larval control programmes. It can contribute to disease transmission in a previously unrecognised manner that can be compounded by environmental changes caused by expanding populations in coastal zones, climate change and rising sea levels due to global warming. Increased disease transmission in coastal areas will also lead to higher disease incidence in inland areas. Many countries in South and Southeast Asia have long coastlines, a high proportion of coastal zone relative to total land area and a large proportion of the population living in coastal areas. Hence, the region is particularly vulnerable to disease transmission by brackish water vectors. Appropriate policies and strategies need to be developed in a local, national and international context to counter this threat to human health in South and Southeast Asia.