Species Identity, Life History, and Geographic Distance Influence Gut Bacterial Communities in Lab-Reared and European Field-Collected Culicoides Biting midges

Tim W R Möhlmann,Constantianus J M Koenraadt,Els H Nijhuis,Dennis E Te Beest,Marc Hendriks,Sven Warris,Barbara S Drolet,Leo Van Overbeek,Cajo J F Ter Braak

doi:10.1007/s00248-021-01822-8

Abstract

Bacteria are part of the insect gut system and influence many physiological traits of their host. Gut bacteria may even reduce or block the transmission of arboviruses in several species of arthropod vectors. Culicoides biting midges are important arboviral vectors of several livestock and wildlife diseases, yet limited information is available on their gut bacterial communities. Addressing this gap will help inform how these communities can be manipulated and ultimately used as novel tools to control pathogens. To assess how bacterial communities change during the life stages of lab-reared C. nubeculosus and C. sonorensis, endosymbiotic bacteria were identified using Illumina sequencing of 16S rRNA and taxonomically characterised. Analyses were conducted to determine how gut bacterial communities in adults are influenced by species identity and geographic distance among biting midge populations. Communities of the two lab-reared Culicoides species significantly changed after pupation and with maturation into 6-day-old adults. Pseudomonas, Burkholderiaceae and Leucobacter bacteria were part of a core community that was trans-stadially transmitted and found throughout their life cycle. Among field-collected biting midges, the bacterial communities were unique for almost each species. Cardinium, Rickettsia and Wolbachia were some of the most abundant bacteria in midges collected from wetlands. Only Pseudomonas was present in high relative abundance in all field-collected species. In this study, species identity, as well as geographic distance, influenced the gut bacterial communities and may partly explain known inter- and intra-species variability in vector competence. Additionally, stably associated bacterial species could be candidates for paratransgenic strategies to control vector-borne pathogens.

Highlights

Culicoides biting midges are the most important vectors of pathogens that cause animal diseases such as African horse sickness, bluetongue, epizootic hemorrhagic disease and Schmallenberg
To gain insight in the origin of gut bacterial communities in adult female biting midges, the bacterial communities in eggs, larvae, pupae and adults were determined for C. nubeculosus and C. sonorensis
Two amplicon sequence variants (ASVs) that belong to the Pseudomonas and Leucobacter genera were identified in all C. nubeculosus life stages (Fig. 2A)

Summary

Introduction

Culicoides biting midges are the most important vectors of pathogens that cause animal diseases such as African horse sickness, bluetongue, epizootic hemorrhagic disease and Schmallenberg Outbreaks of these diseases have a tremendous impact on livestock welfare and cause considerable economic losses due to animal mortality and world-wide trade restrictions to control outbreaks [1,2,3]. Other methods to reduce disease transmission include the control of biting midges by targeting their larval habitats or adult resting sites, the application of repellents or insecticides on host animals or the housing of livestock in screened (midge-proof) buildings. Recent studies show the potential of endosymbiotic bacteria that reduce or block transmission of viruses by arthropod vectors [8,9,10]

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Discussion

Conclusion