A study on transovarial transmission of dengue type 1 virus in Aedes aegypti

The main purpose of this study is to determine the possibility of transovarial transmission of dengue type 1 virus, which was isolated from the serum of a patient with dengue fever during the 1987 dengue epidemic in southern Taiwan, in Aedes aegypti of Kaohsiung strain (KH). Parent female mosquitoes were inoculated with dengue 1 virus by intrathoracic inoculation technique. The F1 offspring adults collected from three sequential ovarian cycles were pooled to become 51, 13 and 14 pools, respectively. All pools were individually inoculated into C6/36 cells and then were detected by direct immunofluorescence antibody technique. Ten, five and three pools, respectively, among these three ovarian cycles turned out to be positive. It revealed that the minimum infection rates (MIR), were 1:254.6 (2,546 mosquitoes), 1:133.6 (668 mosquitoes) and 1:238 (714 mosquitoes), respectively. Meanwhile, the estimated filial infection rates were calculated to be 0.44%, 0.97% and 0.48%, respectively. Since viral antigen has been detected in the tissue of maturing eggs within ovarioles, the results exhibited the possibility that dengue type 1 virus can be transovarially transmitted to the next generation.