High Temperature Cycles Result in Maternal Transmission and Dengue Infection Differences Between <i>Wolbachia</i> Strains in Aedes aegypti

Abstract

Environmental factors play a crucial role in the population dynamics of arthropod endosymbionts, and therefore in the deployment of <i>Wolbachia</i> symbionts for the control of dengue arboviruses. The potential of <i>Wolbachia</i> to invade, persist, and block virus transmission depends in part on its intracellular density. Several recent studies have highlighted the importance of larval rearing temperature in modulating <i>Wolbachia</i> densities in adults, suggesting that elevated temperatures can severely impact some strains, while having little effect on others. The effect of a replicated tropical heat cycle on <i>Wolbachia</i> density and levels of virus blocking was assessed using Aedes aegypti lines carrying strains <i>w</i>Mel and <i>w</i>AlbB, two <i>Wolbachia</i> strains currently used for dengue control. Impacts on intracellular density, maternal transmission fidelity, and dengue inhibition capacity were observed for <i>w</i>Mel. In contrast, <i>w</i>AlbB-carrying <i>Ae. aegypti</i> maintained a relatively constant intracellular density at high temperatures and conserved its capacity to inhibit dengue. Following larval heat treatment, <i>w</i>Mel showed a degree of density recovery in aging adults, although this was compromised by elevated air temperatures. <b>IMPORTANCE</b> In the past decades, dengue incidence has dramatically increased all over the world. An emerging dengue control strategy utilizes Aedes aegypti mosquitoes artificially transinfected with the bacterial symbiont <i>Wolbachia</i>, with the ultimate aim of replacing wild mosquito populations. However, the rearing temperature of mosquito larvae is known to impact on some <i>Wolbachia</i> strains. In this study, we compared the effects of a temperature cycle mimicking natural breeding sites in tropical climates on two <i>Wolbachia</i> strains, currently used for open field trials. When choosing the <i>Wolbachia</i> strain to be used in a dengue control program it is important to consider the effects of environmental temperatures on invasiveness and virus inhibition. These results underline the significance of understanding the impact of environmental factors on released mosquitoes, in order to ensure the most efficient strategy for dengue control.