Remue, L. | Search bioRxiv

bioRxiv2023

Identification of culturable fungi and bacteria in mosquito saliva and impact on arbovirus infection in vitro

Mosquito saliva plays a key role in arbovirus transmission and pathogenesis. This study isolated and identified culturable fungal and bacterial colonies from saliva harvested from Aedes aegypti (lab strain) and Culex pipiens (field-collected) mosquitoes. For the first time, Penicillium crustosum was identified in mosquito saliva. Culturable bacteria detected in mosquito saliva included Serratia marcescens, Serratia nematodiphila, Enterobacter spp., and Klebsiella spp., which were previously identified as mosquito or insect endosymbionts in the midgut or other organs. Analysis with 16S metagenomics showed that the bacterial community in saliva appeared more diverse than the bacterial communities in midguts. Blood feeding did not affect the fungal or bacterial load in mosquito saliva. Oral treatment of adult mosquitoes with antibiotics or an antifungal drug resulted in a significant reduction of resp. bacteria or fungi present in the mosquito saliva. Co-incubation of Semliki Forest virus with saliva from antibiotic or antifungal treated mosquitoes triggered a decrease in viral infection in human skin fibroblasts compared to non-treated saliva. This work lays the foundation for further exploration of the impact of fungi and bacteria in mosquito saliva on both vector competence and arbovirus infection in the mammalian host.

microbiology↗

bioRxiv2022

First report of kdr L1014F and ace-1 G119S insecticide resistance in Belgian Culex mosquitoes

The emergence of West Nile virus and Usutu virus in Europe poses a significant risk to public health. In the absence of efficient antiviral therapy or vaccine candidates, the only strategy to control these arboviruses is to target the Culex (Diptera: Culicidae) mosquito vector. However, the selection pressure caused by exposure to insecticides for vector control or agricultural pest control can lead to insecticide resistance, thereby reducing the efficacy of insecticide-based vector control interventions. In Culex mosquitoes, two of the most common amino acid substitutions associated with insecticide resistance are the kdr L1014F in voltage gated sodium channels and G119S in acetylcholinesterase. In this study, Culex pipiens biotype pipiens, Culex torrentium, and Culex modestus were sampled from 2019 to 2021 in three distinct environmental habitats (urban, peri-urban, and agricultural) in and around the city of Leuven, Belgium. Individual mosquitoes were screened for two mutations resulting in L1014F and G119S amino acid substitutions. Both mutations were observed in Culex pipiens and Culex modestus but not in Culex torrentium mosquitoes across the four collection sites. Furthermore, multi-resistance or cross-resistance in Culex pipiens could be a threat in these areas, as both mutations were observed at low frequencies. These results provide the first report of kdr L1014F and ace-1 G119S resistance in Culex pipiens and Culex modestus mosquitoes from Belgium, highlighting the importance of mosquito surveillance to design effective arbovirus outbreak control strategies.

molecular biology↗