Persistent infection of a novel Picornavirus in the microplanarian Stenostomum leucops (Catenulida).

We present the genome sequence, organization and evidence of persistence of a new picornavirus infecting the flatworm Stenostomum leucops . The complete genome sequence belongs to a virus with a positive single-stranded RNA genome encoding three open reading frames (ORFs) flanked by untranslated regions and polyadenylated termination. The ORFs encode conserved protein motifs typical of the picornavirus superfamily. Phylogenetic analyses confirm membership of this viral superfamily, with closely related viral species found in Biomphalaria (Mollusca) in France and a virus detected in metagenomic analyses of water sources from the USA, suggesting widespread distribution. RT-PCR analysis revealed that this virus persists in a laboratory-grown worm isolate for at least five years, indicating persistent infection. However, no deleterious effects were observed in the infected worms, suggesting a commensalistic or mutualistic relationship between the virus and the worms.