Wolbachia w Mel strain-mediated effects on dengue virus vertical transmission from Aedes aegypti to their offspring

Background Dengue virus serotypes (DENV-1 to -4) can be transmitted vertically in Aedes aegpti mosquitoes. Whether infection with the w Mel strain of the endosymbiont Wolbachia can reduce the incidence of vertical transmission of DENV from infected females to their offspring is not well understood. Methods A laboratory colony of Vietnamese Ae. aegypti , both with and without w Mel infection, were infected with DENV-1 by intrathoracic injection (IT) to estimate the rate of vertical transmission (VT) of the virus. VT in the DENV-infected mosquitoes was calculated via the infection rate estimation from mosquito pool data using maximum likelihood estimation (MLE). Results In 6047 F1 Vietnamese wild-type Ae. aegypti , the MLE of DENV-1 infection was 1.49 per 1000 mosquitoes (95% confidence interval [CI] 0.73–2.74). In 5500 w Mel-infected Ae. aegypti , the MLE infection rate was 0 (95% CI 0–0.69). The VT rates between mosquito lines showed a statistically significant difference. Conclusions The results reinforce the view that VT is a rare event in wild-type mosquitoes and that infection with w Mel is effective in reducing VT. Graphical Abstract