School of Veterinary Science, University of Sydney, Camden, NSW, 2570, Australia.
Laboratoire des Sciences de l'Environnement Marin (LEMAR), UMR 6539 CNRS/UBO/IRD/IFREMER, Institut Universitaire Européen de la Mer, Technopôle Brest-Iroise, 29280, Plouzané, France.
Vet Res. 2018 Apr 10;49(1):34. doi: 10.1186/s13567-018-0529-7.
Marine herpesviruses are responsible for epizootics in economically, ecologically and culturally significant taxa. The recent emergence of microvariants of Ostreid herpesvirus 1 (OsHV-1) in Pacific oysters Crassostrea gigas has resulted in socioeconomic losses in Europe, New Zealand and Australia however, there is no information on their origin or mode of transmission. These factors need to be understood because they influence the way the disease may be prevented and controlled. Mortality data obtained from experimental populations of C. gigas during natural epizootics of OsHV-1 disease in Australia were analysed qualitatively. In addition we compared actual mortality data with those from a Reed-Frost model of direct transmission and analysed incubation periods using Sartwell's method to test for the type of epizootic, point source or propagating. We concluded that outbreaks were initiated from an unknown environmental source which is unlikely to be farmed oysters in the same estuary. While direct oyster-to-oyster transmission may occur in larger oysters if they are in close proximity (< 40 cm), it did not explain the observed epizootics, point source exposure and indirect transmission being more common and important. A conceptual model is proposed for OsHV-1 index case source and transmission, leading to endemicity with recurrent seasonal outbreaks. The findings suggest that prevention and control of OsHV-1 in C. gigas will require multiple interventions. OsHV-1 in C. gigas, which is a sedentary animal once beyond the larval stage, is an informative model when considering marine host-herpesvirus relationships.
海洋疱疹病毒是造成经济、生态和文化重要分类群中流行病的原因。最近，牡蛎疱疹病毒 1（OsHV-1）的微变体在太平洋牡蛎 Crassostrea gigas 中出现，导致欧洲、新西兰和澳大利亚的社会经济损失，然而，关于它们的起源或传播方式的信息却没有。这些因素需要了解，因为它们会影响疾病预防和控制的方式。对澳大利亚 OsHV-1 疾病自然流行期间从 C. gigas 实验种群中获得的死亡率数据进行了定性分析。此外，我们将实际死亡率数据与直接传播的 Reed-Frost 模型进行了比较，并使用 Sartwell 方法分析了潜伏期，以检验流行的类型，是点状来源还是传播性来源。我们的结论是，疫情是由未知的环境来源引发的，而不太可能是同一河口的养殖牡蛎。虽然在较大的牡蛎中，如果它们彼此靠近（<40 厘米），可能会发生直接的牡蛎间传播，但这并不能解释所观察到的流行病、点状暴露和间接传播更为常见和重要的现象。提出了一个关于 OsHV-1 起始病例源和传播的概念模型，导致地方性疾病伴有周期性的季节性暴发。研究结果表明，要预防和控制 C. gigas 中的 OsHV-1，需要采取多种干预措施。对于牡蛎来说，一旦幼虫阶段结束，它们就是一种定居动物，因此在考虑海洋宿主-疱疹病毒关系时，OsHV-1 是一个信息丰富的模型。
