Aquaculture Research Institute, University of Maine, Hitchner Hall, Orono, Maine, United States of America.
School of Marine Sciences, The University of Maine, Hitchner Hall, Orono, Maine, United States of America.
PLoS One. 2019 Jan 16;14(1):e0209178. doi: 10.1371/journal.pone.0209178. eCollection 2019.
The role of parasitic sea lice (Siphonostomatoida; Caligidae), especially Lepeophtheirus salmonis, in the epidemiology of Infectious Salmon Anemia Virus (ISAv) has long been suspected. The epidemiological studies conducted during the 1998 major Infectious Salmon Anaemia (ISA) outbreak in Scotland demonstrated a strong correlation between sea lice presence and ISAv positive sites or subsequent clinical outbreaks of ISA. The question posed from this observation was "do sea lice infestations on Atlantic salmon make them more susceptible to viral infections?" This study investigated the role that sea lice infestations have on the severity of ISAv infections and disease mortality in experimental populations of farmed Atlantic salmon (Salmo salar). A series of experiments was carried out that investigated the potential of sea lice to modify the outcome of an ISAv infection. Experimental populations of Atlantic salmon were established that had: no lice and no ISAv, a single infection with either ISAv or lice and a co-infection with lice then ISAV. The results were quite clear, the process of infestation by the parasite prior to ISAv exposure significantly increased the mortality and death rates of Atlantic salmon, when compared to uninfected controls and ISAv infected groups only. This was consistent over two source strains of Atlantic salmon (Pennobscot and Saint John River), but the severity and timing was altered. Immunological responses were also consistent in that pro-inflammatory genes were induced in lice only and co-infected fish, whereas the anti-viral response, Mx, MH class I β, Galectin 9 and TRIM 16, 25 genes were down-regulated by lice infection prior to and shortly after co-infection with ISAv. It is concluded that the sea lice settlement on Atlantic salmon and the parasite's subsequent manipulation of the host's immune system, which increases parasite settlement success, also increased susceptibility to ISAv.
寄生虫性海虱（Siphonostomatoida；Caligidae），特别是鲑鱼虱（Lepeophtheirus salmonis），在传染性鲑鱼贫血病毒（ISAv）的流行病学中一直被怀疑起作用。1998 年苏格兰发生的重大传染性鲑鱼贫血症（ISA）疫情期间进行的流行病学研究表明，海虱的存在与 ISAv 阳性地点或随后的 ISA 临床暴发之间存在很强的相关性。从这一观察结果中提出的问题是：“海虱的寄生是否会使大西洋鲑鱼更容易感染病毒？”本研究调查了海虱的寄生对养殖大西洋鲑（Salmo salar）实验种群中 ISAv 感染的严重程度和疾病死亡率的影响。进行了一系列实验，以研究海虱是否有可能改变 ISAv 感染的结果。建立了实验性大西洋鲑种群，这些种群没有：虱和 ISAv、仅感染 ISAv 或虱、虱和 ISAv 同时感染。结果非常明显，与未感染对照和仅感染 ISAv 的群体相比，在暴露于 ISAv 之前，寄生虫的寄生过程显著增加了大西洋鲑的死亡率和病死率。这在两个大西洋鲑来源品系（彭诺克斯科特和圣约翰河）中都是一致的，但严重程度和时间有所改变。免疫反应也一致，即炎症前基因仅在虱和混合感染的鱼类中被诱导，而抗病毒反应，Mx、MH 类 Iβ、半乳糖凝集素 9 和 TRIM 16、25 基因在与 ISAv 混合感染之前和之后不久被虱感染下调。结论是，海虱在大西洋鲑鱼上的定居以及寄生虫随后对宿主免疫系统的操纵，增加了寄生虫的定居成功率，也增加了对 ISAv 的易感性。
