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Hong Liu

Publications and source records attributed to Hong Liu.

5 recordsLinked to original sources
USGS2022

Comparative virulence of spring viremia of carp virus (SVCV) genotypes in two koi varieties

Spring viremia of carp virus (SVCV), is a lethal freshwater pathogen of cyprinid fish, and Cyprinus carpio koi is a primary host species. The virus was initially described in the 1960s after outbreaks occurred in Europe, but a global expansion of SVCV has been ongoing since the late 1990s. Genetic typing of SVCV isolates separates them into 4 genotypes that are correlated with geographic origin: Ia (Asia), Ib and Ic (Eastern Europe), and Id (Central Europe). We compared infectivity and virulence of 8 SVCV strains, including 4 uncharacterized Chinese Ia isolates and representatives of genotypes Ia-d in 2 morphologically distinct varieties of koi: long-fin semi-scaled Beni Kikokuryu koi and short-fin fully scaled Sanke koi. Mortality ranged from 4 to 82% in the Beni Kikokuryu koi and 0 to 94% in the Sanke koi following immersion challenge. Genotype Ia isolates of Asian origin had a wide range in virulence (0-94%). Single isolates representing the European genotypes Ib and Ic were moderately virulent (38-56%). Each virus strain produced similar levels of mortality in both koi breeds, with the exception of the SVCV Id strain that appeared to have both moderate and high virulence phenotypes (60% in Beni Kikokuryu koi vs. 87% in Sanke koi). Overall SVCV strain virulence appeared to be a dominant factor in determining disease outcomes, whereas intraspecies variation, based on koi variety, had less of an impact. This study is the first side-by-side comparison of Chinese SVCV isolates and genotype Ia-d strain virulence in a highly susceptible host.

Disease of Aquatic Organisms↗
USGS2018

Insight into infectious hematopoietic necrosis virus (IHNV) in Chinese rainbow trout aquaculture from virus isolated from 7 provinces in 2010–2014

The aquatic rhabdovirus infectious hematopoietic necrosis virus (IHNV) currently causes substantial fish losses in Chinese coldwater aquaculture. While IHNV was first reported in China in 1985 and has since undergone considerable spread, little is known about the underlying epidemiological patterns like introduction sources and transmission routes. In this study, we examined epidemiological and phylogenetic data for 50 IHNV isolates from 7 provinces in China detected in 2010–2014 (Liaoning, n = 33; Jilin, n = 3; Heilongjiang, n = 1; Yunnan, n = 2; Sichuan, n = 1; Hebei, n = 5; Gansu, n = 5). Features of case details include highest mortality associated with water temperatures of 8–10 °C and symptomatic disease observed in adult rainbow trout. Sequence comparisons of the midG sequences of 50 strains revealed 11 different sequence types. One sequence type, mG801J, was predominantly detected, being found in 38 of 50 isolates. Phylogenetic analyses of the new midG sequence types showed that 49 of 50 IHNV isolates are closely related to one another and all descend from the previously described J Nagano subgroup, forming the monophyletic group J Nagano-China clade . This indicates that the majority of IHNV circulating within China is descended from a single importation event from elsewhere in Asia. The one observed exception was the detection of a novel genotype belonging to the previously described MN subgroup. This genotype was identified in Liaoning province, and indicates a second introduction event, one that does not appear to have resulted in diversification and spread. These results indicate that continued surveillance of IHNV in China is necessary to understand and manage viral transmission dynamics within China over time.

Aquaculture↗
USGS2017

Analytical validation of a reverse transcriptase droplet digital PCR (RT-ddPCR) for quantitative detection of infectious hematopoietic necrosis virus

Infectious hematopoietic necrosis virus (IHNV) is an important pathogen of salmonid fishes. A validated universal reverse transcriptase quantitative PCR (RT-qPCR) assay that can quantify levels of IHNV in fish tissues has been previously reported. In the present study, we adapted the published set of IHNV primers and probe for use in a reverse-transcriptase droplet digital PCR (RT-ddPCR) assay for quantification of the virus in fish tissue samples. The RT-ddPCR and RT-qPCR assays detected 13 phylogenetically diverse IHNV strains, but neither assay produced detectable amplification when RNA from other fish viruses was used. The RT-ddPCR assay had a limit of detection (LOD) equating to 2.2 plaque forming units (PFU)/μl while the LOD for the RT-qPCR was 0.2 PFU/μl. Good agreement (69.4–100%) between assays was observed when used to detect IHNV RNA in cell culture supernatant and tissues from IHNV infected rainbow trout ( Oncorhynchus mykiss ) and arctic char ( Salvelinus alpinus ). Estimates of RNA copy number produced by the two assays were significantly correlated but the RT-qPCR consistently produced higher estimates than the RT-ddPCR. The analytical properties of the N gene RT-ddPCR test indicated that this method may be useful to assess IHNV RNA copy number for research and diagnostic purposes. Future work is needed to establish the within and between laboratory diagnostic performance of the RT-ddPCR assay.

Journal of Virological Methods↗