Exploration of the Ixodes ricinus virosphere unveils an extensive virus diversity including novel coltiviruses and other reoviruses.

Bert Vanmechelen,Marijn Thijssen,Joan Martí-Carreras,Edwin Claerebout,Valentijn Vergote,Lies Laenen,Piet Maes,Michelle Merino

doi:10.1093/ve/veab066

Abstract

Recent metagenomics studies have revealed several tick species to host a variety of previously undiscovered RNA viruses. Ixodes ricinus, which is known to be a vector for many viral, bacterial, and protozoan pathogens, is the most prevalent tick species in Europe. For this study, we decided to investigate the virosphere of Belgian I. ricinus ticks. High-throughput sequencing of tick pools collected from six different sampling sites revealed the presence of viruses belonging to many different viral orders and families, including Mononegavirales, Bunyavirales, Partitiviridae, and Reoviridae. Of particular interest was the detection of several new reoviruses, two of which cluster together with members of the genus Coltivirus. This includes a new strain of Eyach virus, a known causative agent of tick-borne encephalitis. All genome segments of this new strain are highly similar to those of previously published Eyach virus genomes, except for the fourth segment, encoding VP4, which is markedly more dissimilar, potentially indicating the occurrence of a genetic reassortment. Further polymerase chain reaction–based screening of over 230 tick pools for 14 selected viruses showed that most viruses could be found in all six sampling sites, indicating the wide spread of these viruses throughout the Belgian tick population. Taken together, these results illustrate the role of ticks as important virus reservoirs, highlighting the need for adequate tick control measures.

Highlights

Recent metagenomics studies have revealed the extensive virus diversity within arthropods [1,2]
As ticks are known vectors of important viral zoonoses, mapping the diversity of viruses carried by ticks can aid in identifying the origin of yet unidentified or emerging zoonoses
We report the discovery of several novel viruses found in I. ricinus

Summary

Introduction

Recent metagenomics studies have revealed the extensive virus diversity within arthropods [1,2]. Of particular interest amongst arthropods are the hematophagous vectors These animals feed on the blood of vertebrate hosts, presenting the ideal conditions for the transmission of pathogens. Ticks are known to carry a diverse range of pathogens, including protozoa, bacteria, helminths and viruses, in Europe they are predominantly known for their ability to transmit Borrelia burgdorferi bacteria, the causative agent for Lyme disease [4,5,6]. Many articles have been published looking at the virus diversity in different tick species in different regions, revealing the presence of many previously undiscovered viruses [8,9,10,11,12,13,14]. Estimating the relative risk of these novel viruses for human, animal and plant health is difficult, their phylogenetic clustering within specific virus families and genera that are known to harbour tick-borne human, animal and plant pathogens (Reoviridae, Nairoviridae, Flaviviridae, Phenuiviridae ...) hints at pathogenic potential for at least some of them

Methods

Results

Conclusion