Characterization of a new member of Iridoviridae, Shrimp hemocyte iridescent virus (SHIV), found in white leg shrimp (Litopenaeus vannamei)

Abstract

A newly discovered iridescent virus that causes severe disease and high mortality in farmed Litopenaeus vannamei in Zhejiang, China, has been verified and temporarily specified as shrimp hemocyte iridescent virus (SHIV). Histopathological examination revealed basophilic inclusions and pyknosis in hematopoietic tissue and hemocytes in gills, hepatopancreas, periopods and muscle. Using viral metagenomics sequencing, we obtained partial sequences annotated as potential iridoviridae. Phylogenetic analyses using amino acid sequences of major capsid protein (MCP) and ATPase revealed that it is a new iridescent virus but does not belong to the five known genera of Iridoviridae. Transmission electron microscopy showed that the virus exhibited a typical icosahedral structure with a mean diameter of 158.6 ± 12.5 nm (n = 30)(v-v) and 143.6 ± 10.8 nm (n = 30)(f-f), and an 85.8 ± 6.0 nm (n = 30) nucleoid. Challenge tests of L. vannamei via intermuscular injection, per os and reverse gavage all exhibited 100% cumulative mortality rates. The in situ hybridization showed that hemopoietic tissue, gills, and hepatopancreatic sinus were the positively reacting tissues. Additionally, a specific nested PCR assay was developed. PCR results revealed that L. vannamei, Fenneropenaeus chinensis, and Macrobrachium rosenbergii were SHIV-positive, indicating a new threat existing in the shrimp farming industry in China.

RNAi screening identifies a new Toll from shrimp that restricts WSSV infection through activating Dorsal to induce antimicrobial peptides

“…Shrimps ( L. vannamei , average weight 8 g each) were purchased from the local shrimp farm in Zhuhai, Guangdong Province, China, and fed with a commercial diet in a recirculating water tank system filled with air-pumped sea water (2.5% salinity) at 28 °C. Before all experiment treatments, the shrimps (5% of total) were detected and confirmed to be free of common pathogens including white spot syndrome virus (WSSV), yellow head virus (YHV), taura syndrome virus (TSV), shrimp hemocyte iridescent virus (SHIV, also known as CQIV), infectious hypodemal and hematopoietic necrosis virus (IHHNV) and Vibrio parahaemolyticus by PCR or RT-PCR methods according to standard operation procedures by Panichareon et al (71) and Qiu et al (72). Because many genes from the shrimp canonical Toll-Dorsal pathway can be activated by Gram-negative (G - ) bacteria (42, 46), V. parahaemolyticus thus was used here as a positive activator of the shrimp Toll-Dorsal pathway.…”

Metagenomics revealing new virus species in farm and pet animals and aquaculture

“…Partial sequences were obtained by viral metagenomics, and phylogenetic calculations based on the sequences of major capsid protein and ATPase showed that SHIV is a new iridescent virus, which could not be clustered into any of the five known genera of Iridoviridae. Based on the sequences a diagnostic PCR was developed for detecting this novel virus threatening shrimp farming industry in China (Qiu et al, 2017).…”

First Description of a Natural Infection with Shrimp Hemocyte Iridescent Virus in Farmed Giant Freshwater Prawn, <em>Macrobrachium Rosenbergii</em>

“…Globally, viral diseases have been acknowledged as a huge threat to shrimp aquaculture industry. Among the viruses reported for crustacean, Shrimp hemocyte iridescent virus (SHIV) was a newly found virus isolated from diseased white leg shrimp Penaeus vannamei in December of 2014 in Zhejiang Province of China, which can cause massive mortality to P. vannamei [1], the most important crustacean for global aquaculture. The virus has a typical icosahedral structure with a mean diameter around 150 nm [1].…”

“…Among the viruses reported for crustacean, Shrimp hemocyte iridescent virus (SHIV) was a newly found virus isolated from diseased white leg shrimp Penaeus vannamei in December of 2014 in Zhejiang Province of China, which can cause massive mortality to P. vannamei [1], the most important crustacean for global aquaculture. The virus has a typical icosahedral structure with a mean diameter around 150 nm [1]. Evidences from histopathological study, transmission electron microscope (TEM) of ultrathin sections, and in situ hybridization (ISH) indicated that SHIV may mainly infect the hematopoietic tissue and hemocytes in P. vannamei [1].…”

“…The virus has a typical icosahedral structure with a mean diameter around 150 nm [1]. Evidences from histopathological study, transmission electron microscope (TEM) of ultrathin sections, and in situ hybridization (ISH) indicated that SHIV may mainly infect the hematopoietic tissue and hemocytes in P. vannamei [1]. SHIV has a double-stranded DNA genome of 165,809 bp.…”