Evidence of vertical transmission of dengue virus in two endemic localities in the state of Oaxaca, Mexico

Background: Dengue virus is spread in tropical areas of the world and is the causative agent of dengue fever and dengue hemorrhagic fever. It is horizontally transmitted to humans by infected Aedes mosquitoes, but it is also able to be vertically or transovarially transmitted to insect progeny. Objective: In this work, we analyzed the vertical transmission of dengue virus in Aedes aegypti mosquitoes collected in two endemic localities in the state of Oaxaca, Mexico. Methods: The collected larvae were grown in the laboratory and transovarial transmission of dengue virus, either in larvae or newly emerged mosquitoes, was investigated using a semi-nested reverse transcription- polymerase chain reaction method. Results: Although the presence of dengue virus in larvae could not be demonstrated, the viral genome was amplified in 4 out of 43 pools of in-cage born mosquitoes: DEN 2, 3 and 4 serotypes were detected in 2 pools from Tuxtepec and two from Juchitán. Conclusion: The results presented here strongly suggest that dengue virus can be vertically transmitted in mosquitoes from Oaxaca, but more studies will be necessary to analyze the epidemiological impact of this mechanism of transmission.