Aldrin M, Huseby R B, Bang Jensen B, Jansen M D
Norwegian Computing Center, P.O.Box 114 Blindern, N-0314 Oslo, Norway.
Norwegian Veterinary Institute, P.O. Box 750 Sentrum, N-0106 Oslo, Norway.
Prev Vet Med. 2021 Jun;191:105360. doi: 10.1016/j.prevetmed.2021.105360. Epub 2021 Apr 16.
Infectious salmon anaemia (ISA) is an important viral disease causing economic losses and reduced welfare in farmed Atlantic salmon. Here, we present a spatio-temporal stochastic model for the spread of ISA between and within marine aquaculture farms. The model is estimated on historical production data for all marine salmonid farms in Norway from 2004 to February 2019. In this time 142 outbreaks of ISA occurred. We find that transmission from infected neighbouring farms accounts for around 50% of the infections, whereas transmission from "non-specified sources" accounts for around 40%. We hypothesise that the most important of the latter are viruses mutating from the non-virulent ISAV HPR0 to the virulent ISAV HPRdel. The model is used for scenario simulation, or what-if analysis, to investigate the effects of potential strategies to combat ISA, including screening, vaccination and culling. Changing from the current strategy of culling farms with detected ISA-outbreaks to mandatory screening and culling when virus is detected will reduce the fraction of cohorts with a clinical ISA outbreak from 3.8 to 0.36%. Introducing mandatory vaccination would have approximately the same effect as the current stamping-out strategy. The scenario simulation is a useful tool for deciding on appropriate mitigation measures.
传染性鲑鱼贫血症（ISA）是一种重要的病毒性疾病，会给养殖的大西洋鲑鱼带来经济损失并降低其健康水平。在此，我们提出了一个关于ISA在海洋水产养殖场之间及场内传播的时空随机模型。该模型是根据2004年至2019年2月挪威所有海洋鲑鱼养殖场的历史生产数据估算得出的。在此期间，共发生了142起ISA疫情。我们发现，来自受感染相邻养殖场的传播约占感染病例的50%，而来自“未明确来源”的传播约占40%。我们推测，后者中最重要的是病毒从无毒的ISA病毒HPR0毒株变异为有毒的ISA病毒HPRdel毒株。该模型用于情景模拟，即假设分析，以研究对抗ISA的潜在策略的效果，包括筛查、疫苗接种和扑杀。从当前对检测到ISA疫情的养殖场进行扑杀的策略转变为在检测到病毒时进行强制筛查和扑杀，将使出现临床ISA疫情的鱼群比例从3.8%降至0.36%。引入强制疫苗接种的效果与当前的扑杀策略大致相同。情景模拟是决定适当缓解措施的有用工具。
