Abstract:
Background & objectives: Aedes aegypti and Ae. albopictus are major arboviral vectors that are considered to lay
eggs, and undergo preimaginal development only in fresh water collections. However, recently they have been also
shown to develop in coastal brackish water habitats. The ability of the biologically variant salinity-tolerant Aedes
vectors to transmit arboviral diseases is unknown. We therefore, investigated the infection of salinity-tolerant Aedes
mosquitoes with dengue virus (DENV) and analysed dengue incidence and rainfall data to assess the contribution
of salinity-tolerant Aedes vectors to dengue transmission in the coastal Jaffna peninsula in Sri Lanka.
Methods: Brackish and fresh water developing female Ae. aegypti and Ae. albopictus were tested for their ability to
become infected with DENV through in vitro blood feeding and then transmit DENV vertically to their progeny. An
immunochromatographic test for the NS1 antigen was used to detect DENV. Temporal variation in dengue incidence
in relation to rainfall was analysed for the peninsula and other parts of Sri Lanka.
Results: Aedes aegypti and Ae. albopictus developing in brackish water, became infected with DENV through in
vitro blood feeding and the infected mosquitoes were able to vertically transmit DENV to their progeny. Monsoonal
rainfall was the discernible factor responsible for the seasonal increase in dengue incidence in the peninsula and
elsewhere in Sri Lanka.
Interpretation & conclusion: Fresh water Aedes vectors are main contributors to the increased dengue incidence that
typically follows monsoons in the Jaffna peninsula and elsewhere in Sri Lanka. It is possible however, that brackish
water-developing Aedes constitute a perennial reservoir for DENV to maintain a basal level of dengue transmission
in coastal areas of the peninsula during the dry season, and this supports increased transmission when monsoonal
rains expand populations of fresh water Aedes
