Modelling the impacts of imperfect maternal transmission on the spread of Wolbachia in Ae. aegypti population

Adeshina I. Adekunle, Michael T. Meehan, Emma S. McBryde. Modelling the impacts of imperfect maternal transmission on the spread of Wolbachia in Ae. aegypti population. arXiv preprint arXiv:1809.01538.


Dengue continues to be a significant health burden for individuals living in its endemic region. One of the strategies to reduce this burden requires targeting the vector agent, Ae. aegypti, in which intracellular bacterium Wolbachia has proven to be attractive in achieving this aim. Using Wolbachia-infected (WI) mosquitoes to wipe out the Wolbachia-uninfected (WU) ones comes with a maternal-inherited advantage known as cytoplasmic incompatibility, but Wolbachia itself exerts some fitness cost to their host. Also, the effect of imperfect maternal transmission from the WI mosquitoes could be a factor. Despite the successful introduction of WI Ae. aegypti mosquitoes at a small scale, how the method works and the likelihood of success at a larger scale is not fully understood. In this study, we analyze the invasive prospects of Wolbachia by developing a model that introduces the WI mosquitoes into a wild-type Ae-aegypti population. We study the interactions between key parameters (host fitness and imperfect maternal transmission) that determine whether WI mosquitoes will be suppressed or will dominate. Our analyses show a reproduction fitness threshold exists above which the WI mosquitoes will always dominate, and below which WI mosquitoes may co-exist with the non-Wolbachia infected mosquitoes. We show that cytoplasmic incompatibility alone is not enough for WI mosquitoes to dominate as both its fitness and the possibility of mixed offspring play a critical role. In the absence of WI mosquitoes with greater fitness than the wild-type mosquitoes, small introductions of WI mosquitoes will not lead to invasion. However, under the same circumstances, stable co-existence of both types of mosquito is possible. Hence direct killing of wild-type mosquitoes combined with Wolbachia introduction might be an effective strategy in the fight against dengue.