Virus-derived sequences from the transcriptomes of two snail vectors of schistosomiasis, Biomphalaria pfeifferi and Bulinus globosus from Kenya

PeerJ. 2021 Nov 15;9:e12290. doi: 10.7717/peerj.12290. eCollection 2021.


Schistosomiasis, which infects more than 230 million people, is vectored by freshwater snails. We identified viral sequences in the transcriptomes of Biomphalaria pfeifferi (BP) and Bulinus globosus (BuG), two of the world's most important schistosomiasis vectors in Africa. Sequences from 26 snails generated using Illumina Hi-Seq or 454 sequencing were assembled using Trinity and CAP3 and putative virus sequences were identified using a bioinformatics pipeline. Phylogenetic analyses were performed using viral RNA-dependent RNA polymerase and coat protein sequences to establish relatedness between virus sequences identified and those of known viruses. Viral sequences were identified from the entire snail holobiont, including symbionts, ingested material and organisms passively associated with the snails. Sequences derived from more than 17 different viruses were found including five near full-length genomes, most of which were small RNA viruses with positive sense RNA genomes (i.e., picorna-like viruses) and some of which are likely derived from adherent or ingested diatoms. Based on phylogenetic analysis, five of these viruses (including BPV2 and BuGV2) along with four Biomphalaria glabrata viruses reported previously, cluster with known invertebrate viruses and are putative viruses of snails. The presence of RNA sequences derived from four of these novel viruses in samples was confirmed. Identification of the genome sequences of candidate snail viruses provides a first step toward characterization of additional gastropod viruses, including from species of biomedical significance.

Keywords: Biomphalaria pfeifferi; Bulinus globosus; Diatom/marine virus; Dicistrovirus; Iflavirus; Kenya; RNA virus; Schistosomiasis vector; Snail virus; Virus discovery.

Grant support

This work was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number P30GM110907 and the National Institute of Health (NIH) grant R37AI101438. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.