Characterization of viruses in a tapeworm: phylogenetic position, vertical transmission, and transmission to the parasitized host

Abstract

Parasitic flatworms (Neodermata) infect all vertebrates and represent a significant health and economic burden worldwide due to the debilitating diseases they cause. This study sheds light for the first time into the virome of a tapeworm by describing six novel RNA virus candidate species associated with Schistocephalus solidus, including three negative-strand RNA viruses (order Jingchuvirales, Mononegavirales, and Bunyavirales) and three double-stranded RNA viruses. Using in vitro culture of S. solidus, controlled experimental infections and field sampling, we demonstrate that five of these viruses are vertically transmitted, and persist throughout the S. solidus complex life cycle. Moreover, we show that one of the viruses, named Schistocephalus solidus rhabdovirus (SsRV1), is excreted by the parasite and transmitted to parasitized hosts indicating that it may impact S. solidus-host interactions. In addition, SsRV1 has a basal phylogenetic position relative to vertebrate rhabdoviruses suggesting that parasitic flatworms could have contributed to virus emergence. Viruses similar to four of the S. solidus viruses identified here were found in geographically distant S. solidus populations through data mining. Further studies are necessary to determine if flatworm viruses can replicate in parasitized hosts, how they contribute to parasite infection dynamics and if these viruses could be targeted for treatment of parasitic disease.

The genome of the thin-necked bladder worm Taenia hydatigena reveals evolutionary strategies for helminth survival

“…Given that fitness-based selection and phenotypic plasticity are connected to genome size [18][19][20] , this expanded genome may be related to its strikingly wide host range. Notably, the wide endogenization of various viral genomes into the tapeworm genome suggests previous viral infections 21 , consistent with a recent study that identified six novel RNA viruses that infect the tapeworm Schistocephalus solidus 22 . Importantly, the study proved that the S. solidus rhabdovirus can be transmitted from tapeworms to their parasitized hosts, impacting S. solidus-host interactions.…”

The host phenotype and microbiome varies with infection status, parasite origin and parasite microbiome composition

“…We also provide evidence that some of the parasite-associated bacteria contribute to modulating the host immune system. Recently, we also discovered that viruses are associated with S. solidus and that some of these are transmitted to parasitized hosts, which means that viruses could also impact the host immune response [98]. Further studies are needed to test whether S. solidus relies on these microbes for infection, or whether they are detrimental for the parasite.…”

Recent Advances in Bunyavirus Glycoprotein Research: Precursor Processing, Receptor Binding and Structure

“…Asterisks indicate main branches for which bootstrap support was <0.7. The dataset used for the phylogeny includes all currently assigned bunyavirus families [ 1 ], the grouping of which is broadly in line with that presented in a recently published tree [ 25 ]. The numbered, black lines in the figure denote bunyavirus species currently not assigned to a family [Wuhan spider virus ( 1 ), Laurel lake virus ( 2 ), Hubei blood fluke virus 2 ( 3 ), Hubei blood fluke virus 1 ( 4 ), Mothra virus ( 5 ), Shistocephalus solidus bunya-like virus ( 6 )].…”