Jenkins Cheryl, Hick Paul, Gabor Melinda, Spiers Zoe, Fell Shayne A, Gu Xingnian, Read Andrew, Go Jeffrey, Dove Michael, O'Connor Wayne, Kirkland Peter D, Frances Jane
NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Menangle, Australia.
Dis Aquat Organ. 2013 Jul 22;105(2):109-26. doi: 10.3354/dao02623.
Between November 2010 and January 2011, triploid Crassostrea gigas (Pacific oysters) cultivated in the Georges River, New South Wales, experienced >95% mortality. Mortalities also occurred in wild diploid C. gigas in the Georges River and shortly thereafter in the adjacent Parramatta River estuary upstream from Sydney Harbour. Neighbouring Saccostrea glomerata (Sydney rock oysters) did not experience mortalities in either estuary. Surviving oysters were collected to investigate the cause of mortalities. Histologically all oysters displayed significant pathology, and molecular testing revealed a high prevalence of ostreid herpesvirus-1 (OsHV-1). Quantitative PCR indicated that many C. gigas were carrying a high viral load at the time of sampling, while the load in S. glomerata was significantly lower (p < 0.001). Subsequent in situ hybridisation experiments confirmed the presence of a herpesvirus in C. gigas but not S. glomerata tissues, suggesting that S. glomerata is not susceptible to infection with OsHV-1. Naïve sentinel triploid C. gigas placed in the Georges River estuary in January 2011 quickly became infected and experienced nearly 100% mortality within 2 wk of exposure, indicating the persistence of the virus in the environment. Phylogenetic analysis of sequences derived from the C2/C6 region of the virus revealed that the Australian strain of OsHV-1 belongs to the microvariant (µ-var) cluster, which has been associated with severe mortalities in C. gigas in other countries since 2008. Environmental data revealed that the Woolooware Bay outbreaks occurred during a time of considerable environmental disturbance, with increased water temperatures, heavy rainfall, a toxic phytoplankton bloom and the presence of a pathogenic Vibrio sp. all potentially contributing to oyster stress. This is the first confirmed report of OsHV-1 µ-var related C. gigas mortalities in Australia.
2010年11月至2011年1月期间，新南威尔士州乔治斯河养殖的三倍体太平洋牡蛎（Crassostrea gigas）死亡率超过95%。乔治斯河的野生二倍体太平洋牡蛎也出现了死亡情况，此后不久，悉尼港上游相邻的帕拉马塔河河口也出现了死亡。相邻的悉尼岩牡蛎（Saccostrea glomerata）在这两个河口均未出现死亡。采集存活的牡蛎以调查死亡原因。组织学检查显示，所有牡蛎均有明显病变，分子检测表明牡蛎疱疹病毒-1（OsHV-1）感染率很高。定量PCR表明，许多太平洋牡蛎在采样时携带的病毒载量很高，而悉尼岩牡蛎的病毒载量则显著较低（p < 0.001）。随后的原位杂交实验证实太平洋牡蛎组织中存在疱疹病毒，而悉尼岩牡蛎组织中不存在，这表明悉尼岩牡蛎不易感染OsHV-1。2011年1月放入乔治斯河河口的未感染过病毒的三倍体太平洋牡蛎哨兵很快被感染，在接触病毒后2周内死亡率接近100%，这表明病毒在环境中持续存在。对病毒C2/C6区域序列的系统发育分析表明，澳大利亚的OsHV-1毒株属于微变异株（µ-var）簇，自2008年以来，该毒株在其他国家与太平洋牡蛎的严重死亡有关。环境数据显示，伍卢奥雷湾疫情爆发期间环境干扰较大，水温升高、降雨量大、有毒浮游植物大量繁殖以及致病性弧菌的存在都可能导致牡蛎应激。这是澳大利亚首次证实与OsHV-1 µ-var相关的太平洋牡蛎死亡报告。
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