Kristoffersen A B, Viljugrein H, Kongtorp R T, Brun E, Jansen P A
National Veterinary Institute, P.O. Box 750, Sentrum, Oslo N-0106, Norway.
Prev Vet Med. 2009 Jul 1;90(1-2):127-36. doi: 10.1016/j.prevetmed.2009.04.003. Epub 2009 May 5.
Pancreas disease (PD) is an emerging infectious disease in farmed Atlantic salmon (Salmo salar L.) and rainbow trout (Oncorhynchus mykiss Walbaum) caused by salmonid alphavirus (SAV). The present study is a large scale study aiming at quantifying the probability of contracting PD in farmed salmonid cohorts in Norway due to exposure to risk factors that may be associated with specific transmission pathways for SAV, or may increase a cohort's susceptibility to PD. Monthly reports of numbers of fish and mean fish weight from all marine salmonid farm sites in Norway were used to identify cohorts of farmed salmonids. Only cohorts that were initiated and terminated during 2003-2007 were assembled for the study. Records of clinical diagnosis of PD on marine farm sites were used to identify PD case cohorts. In PD case cohorts, PD-outbreaks were defined to start the month the diagnosis was recorded and last until the cohort was terminated. All cohorts in which PD was not recorded were assigned to the control-class. In total 143 PD case cohorts and 1079 control cohorts were assembled. Risk factors were assigned to the cohorts and analysed using logistic regression by generalized additive models (GAM). We find that infection pressure, a variable designed to capture the potential for local disease spread, has a strong effect on the probability of recording a PD-outbreak in a cohort. The function describing the effect of infection pressure increased steeply as infection pressure increased from 0 to moderate values corresponding to having a mean sized neighbouring fish stock with PD at a distance of 2 km, after which the function levelled off. The study emphasises horizontal transmission pathways as important for the spread of PD in Norwegian salmon farming, and accordingly that bio-security measures aimed at controlling horizontal transmission are necessary in order to reduce the number of outbreaks of PD.
胰腺疾病（PD）是养殖大西洋鲑（Salmo salar L.）和虹鳟（Oncorhynchus mykiss Walbaum）中一种新出现的传染病，由鲑鱼α病毒（SAV）引起。本研究是一项大规模研究，旨在量化挪威养殖鲑鱼群体中因接触可能与SAV特定传播途径相关或可能增加群体对PD易感性的风险因素而感染PD的概率。挪威所有海洋鲑鱼养殖场每月的鱼类数量和平均鱼重报告用于确定养殖鲑鱼群体。仅收集了2003年至2007年期间开始和结束的群体用于该研究。海洋养殖场PD的临床诊断记录用于确定PD病例群体。在PD病例群体中，PD疫情被定义为从诊断记录的月份开始，持续到群体结束。所有未记录PD的群体被归入对照组。总共收集了143个PD病例群体和1079个对照群体。将风险因素分配给这些群体，并使用广义相加模型（GAM）通过逻辑回归进行分析。我们发现，感染压力这一旨在捕捉局部疾病传播潜力的变量，对群体中记录到PD疫情的概率有很强的影响。描述感染压力影响的函数在感染压力从0增加到对应于距离2公里处有平均规模的邻近患有PD的鱼群的中等值时急剧增加，此后该函数趋于平稳。该研究强调水平传播途径对挪威鲑鱼养殖中PD传播的重要性，因此，旨在控制水平传播的生物安全措施对于减少PD疫情的数量是必要的。
