Identification, Virulence, and Molecular Characterization of a Recombinant Isolate of Grass Carp Reovirus Genotype I

Abstract

The hemorrhagic disease of grass carp (HDGC) caused by grass carp reovirus (GCRV) still poses a great threat to the grass carp industry. Isolation and identification of the GCRV genotype I (GCRV-I) has been rarely reported in the past decade. In this study, a new GCRV was isolated from diseased fish with severe symptoms of enteritis and mild hemorrhages on the body surface. The isolate was further identified by cell culture, transmission electron, indirect immunofluorescence, and SDS-PAGE electrophoretic pattern analysis of genomic RNA. The results were consistent with the new isolate as a GCRV-I member and tentatively named GCRV-GZ1208. Both grass carp and rare minnow infected by the GCRV-GZ1208 have no obvious hemorrhagic symptoms, and the final mortality rate was ≤10%, indicating that it may be a low virulent isolate. GZ1208 possessed highest genomic homology to 873/GCHV (GCRV-I) and golden shiner reovirus (GSRV). Additionally, it was found a 90.7–98.3% nucleotide identity, a 96.4–100% amino acid identity, and <50% identity with GCRV-II and III genotypes. Interestingly, the sequences of some segments of GZ1208 were similar to GCRV-8733/GCHV, whereas the remaining segments were more closely related to GSRV, suggesting that a recombination event had occurred. Bootscan analysis of the complete genomic sequence confirmed this hypothesis, and recombination events between 873/GCHV and other GSRV-like viruses were also accompanied by gene mutations.

Structure, function and immune evasion strategies of aquareoviruses, with focus on grass carp reovirus

“…Furthermore, various GCRV isolates have been identified from diseased or healthy grass carp, and are mainly divided into three genotypic groups, including GCRV‐I, GCRV‐II and GCRV‐III (Table 2). Genotype I is characterized as a long latent period, low mortality (42.5%) and obvious infection‐induced cytopathic effects (CPE) 33–38 . Genotype II is associated with a short latent period and can cause high mortality (60%–80%) of grass carp 19,34,39–44 .…”

“…Genotype I is characterized as a long latent period, low mortality (42.5%) and obvious infection-induced cytopathic effects (CPE). [33][34][35][36][37][38] Genotype II is associated with a short latent period and can cause high mortality (60%-80%) of grass carp. 19,34,[39][40][41][42][43][44] Genotype III has typical haemorrhage symptom and propagates in a grass carp kidney cell line with a typical CPE.…”

A Review of Grass Carp and Related Species Literature on Diet, Behavior, Toxicology, and Physiology Focused on Informing Development of Controls for Invasive Grass Carp Populations in North America

“…GCRV-GD1108 is considered nearly avirulent, as it produces low viral loads and does not cause symptoms or mortality [863]. The strain GCRV-GZ1208 primarily causes enteritis with little to no hemorrhaging and has a mortality rate of <10% [867]. Another virulent strain of gentotype II GCRV, HA741, had a mean cumulative mortality rate of 74% over the course of two weeks after exposure [628].…”

New indices for the diagnosis of fish welfare and their application to the grass carp ( Ctenopharyngodon idella ) reared in earthen ponds

“…The grass carp may show various signs that indicate health problems. The main organs affected are the eyes, lips, operculum, skin, swimmers, gills, abdomen and anus (Hoole et al, 2008;Luo et al, 1993Luo et al, , 2015Ni & Wang, 1999;Zeng et al, 2021). Ocular disease is common and can occur as a primary or secondary manifestation of systemic disease.…”