Identification of a novel toti-like virus symbiotic with Giardia duodenalis.

Giardiasis is a parasitic intestinal infection of both animals and humans, caused by the enteric protozoan Giardia duodenalis (syn. G. lamblia and G. intestinalis). To date, symbiont RNA viruses of G. duodenalis: Giardia lamblia virus (GLV) and Giardia duodenalis RNA virus-2 (GdRV-2) have been reported. Here, we report the complete genome sequence of a novel virus identified in a human isolate of G. duodenalis using fragmented and primer-ligated double-stranded RNA sequencing. This virus, designated the Non-GLV Giardia duodenalis ISE strain (Noggi) virus, is genetically distinct from GLV and GdRV-2 and likely represents the third symbiont virus in Giardia parasites.