DAO 118:65-75 (2016)  -  DOI: https://doi.org/10.3354/dao02958

Identification and characterization of ostreid herpesvirus 1 associated with massive mortalities of Scapharca broughtonii broodstocks in China

Changming Bai1,2, Wenhui Gao1, Chongming Wang1,2,*, Tao Yu3, Tianwen Zhang4, Zhaoxing Qiu4, Qingchen Wang1, Jie Huang1,2

1Division of Maricultural Organism Disease Control and Molecular Pathology, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, 106 Nanjing Road, Qingdao 266071, PR China
2Laboratory for Marine Fisheries and Aquaculture, Qingdao National Laboratory for Marine Science and Technology, 1 Wenhai Road, Aoshanwei town, Qingdao 266237, PR China
3Changdao Enhancement and Experiment Station, Chinese Academy of Fishery Sciences, 2 Haibin Road, Changdao county, Yantai 265899, PR China
4Benthic Biology Research Centre, Marine Biology Institute of Shandong Province, 7 Youyun Road, Qingdao 266104, PR China
*Corresponding author:

ABSTRACT: In the early summer of 2012 and 2013, mass mortalities of blood ark shell (Scapharca [Anadara] broughtonii), broodstocks were reported in several hatcheries on the coast of northern China. Clinical signs including slow response, gaping valves and pale visceral mass were observed in diseased individuals. In response to these reported mortalities, 238 samples were collected from hatcheries at 6 sites. Microscopic changes including lysed connective tissue, dilation of the digestive tubules, eosinophilic inclusion bodies, nuclear chromatin margination and pyknosis were found in affected animals. Transmission electron microscopy (TEM) revealed herpes-like viral particles within the connective tissue of the mantle. Quantative PCR (qPCR) and nested PCR (nPCR) analysis using primers specific for ostreid herpesvirus 1 (OsHV-1) indicated significant higher prevalence of OsHV-1 DNA in cases associated with mass mortalities than those without mass mortalities (p = 0.0012 for qPCR, p < 0.0001 for nPCR). qPCR also indicated that samples associated with mass mortalities carried high viral DNA loads, while the loads in apparently healthy samples were significantly lower (t = 3.15, df = 92, p = 0.002). Sequence analysis of the C2/C6 region of nPCR products revealed 5 newly described variants, which were closely related to each other. Phylogenetic analysis of the 5 virus variants and 48 virus variants reported in previous studies identified 2 main phylogenetic groups, and the 5 virus variants identified here were allocated to a separate subclade. To our knowledge, this is the first report of mass mortalities of bivalve broodstocks associated with OsHV-1 infection.

KEY WORDS: Scapharca broughtonii · Herpes-like virus · Ostreid herpesvirus 1 · Mass mortality · Aquaculture

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Cite this article as: Bai C, Gao W, Wang C, Yu T and others (2016) Identification and characterization of ostreid herpesvirus 1 associated with massive mortalities of Scapharca broughtonii broodstocks in China. Dis Aquat Org 118:65-75. https://doi.org/10.3354/dao02958

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