AUTHOR=Alomar Abdullah A. , Pérez-Ramos Daniel W. , Kim Dongmin , Kendziorski Natalie L. , Eastmond Bradley H. , Alto Barry W. , Caragata Eric P. 

TITLE=Native Wolbachia infection and larval competition stress shape fitness and West Nile virus infection in Culex quinquefasciatus mosquitoes

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1138476

DOI=10.3389/fmicb.2023.1138476

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p><italic>Wolbachia</italic> transinfections established in key mosquito vectors, including <italic>Aedes aegypti</italic> are typically associated with pathogen blocking—reduced susceptibility to infection with key pathogens and reduced likelihood those pathogens are transmitted to new hosts. Host-symbiont-virus interactions are less well understood in mosquitoes like <italic>Culex quinquefasciatus</italic>, which naturally harbor <italic>Wolbachia</italic>, with pathogen blocking observed in some populations but not others, potentially due to innate differences in their <italic>Wolbachia</italic> load. In nature, mosquito larvae are often subject to developmental stresses associated with larval competition, which can lead to reduced body size and differential susceptibility to arbovirus infection.</p></sec><sec><title>Methods</title><p>In this study, we sought to understand whether competition stress and <italic>Wolbachia</italic> infection in <italic>Cx. quinquefasciatus</italic> combine to impact host fitness and susceptibility to infection with West Nile virus. We reared <italic>Wolbachia</italic>-infected and uninfected <italic>Cx. quinquefasciatus</italic> larvae under three competition stress levels, increasing larval density without increasing the amount of food supplied. We then monitored larval development and survival, measured wing length and quantified <italic>Wolbachia</italic> density in adults, and then challenged mosquitoes from each treatment group orally with West Nile virus.</p></sec><sec><title>Results and Discussion</title><p>We observed that high competition stress extended development time, decreased the likelihood of eclosion, decreased body size, and increased susceptibility to West Nile virus (WNV) infection. We also observed that <italic>Wolbachia</italic> infection reduced WNV load under low competition stress, and significantly improved the rate of survival for larval reared under higher competition stress. Consequently, our data suggest that native <italic>Wolbachia</italic> infection in <italic>Cx. quinquefasciatus</italic> has differential consequences for host fitness and susceptibility to WNV infection depending on competition stress.</p></sec>