Natural vertical transmission of dengue virus in Aedes albopictus (Diptera: Culicidae) in Kerala, a southern Indian state.

The natural occurrence of vertical transmission of dengue viruses in Aedes albopictus (Skuse) mosquitoes was examined in the state of Kerala in southern India. Adults and larvae of Ae. albopictus collected from Kerala were screened for dengue viruses by using enzyme-linked immunosorbent assay with dengue-specific monoclonal antibodies. The possibility of the vertical transmission of dengue virus in Ae. albopictus was further evidenced by the detection of the virus in field-collected adult males as well as females emerged from field-collected larvae. Two pools, one pool from the adult males and one pool from the emerged females derived from field-collected larvae, were collected in the relatively hot months of June and March, respectively, and found to be positive for dengue virus antigen. Dengue serotype 2 virus was isolated from field-collected male adults in Kerala. These findings suggest that dengue virus is maintained in Ae. albopictus mosquitoes during the dry season by vertical transmission in nature.