Viljugrein H, Staalstrøm A, Molvaelr J, Urke H A, Jansen P A
National Veterinary Institute, P.O. Box 750 Sentrum, 0106 Oslo, Norway.
Dis Aquat Organ. 2009 Dec 22;88(1):35-44. doi: 10.3354/dao02151.
Pancreas disease (PD) is an emerging disease in salmon farming caused by the salmonid alphavirus (SAV). SAV is evidently spread horizontally between neighbouring salmon farms, but whether such transmission occurs by passive drift in the water current or via fomites is not known. We tested whether hydrodynamic modelling contributes to explain the spread of PD, in which case SAV is likely to spread by passive drift. We present a simple logistic regression model that accounts for the effect of PD in the neighbourhood on the probability of acquiring PD in cohorts of farmed salmonids from an area on the west coast of Norway between 2005 and 2008. For a given cohort, we calculated infection pressure (IP) based on Euclidean distance, seaway distance or estimated water contact to sites with PD, and compared the amount of variance explained in the regression model by the different variants of IP. Water contact between a discharging farm site and a receiving site was calculated by simulating particle discharge using a hydrodynamic model. IP estimated by water contact was the best predictor of PD cases and controls in the model, which performed significantly better than IP estimated by seaway distance or Euclidean distance. Since the spread of PD in the study area was best explained by modelled water velocity, we conclude that PD is likely to be spread by passive drift of SAV in the water current.
胰腺疾病（PD）是鲑鱼养殖中一种由鲑鱼α病毒（SAV）引起的新出现的疾病。SAV显然在相邻的鲑鱼养殖场之间水平传播，但这种传播是通过水流中的被动漂移还是通过污染物传播尚不清楚。我们测试了水动力模型是否有助于解释PD的传播，在这种情况下，SAV可能通过被动漂移传播。我们提出了一个简单的逻辑回归模型，该模型考虑了挪威西海岸一个地区2005年至2008年养殖鲑鱼群体中附近地区PD对感染PD概率的影响。对于给定的群体，我们根据欧几里得距离、航道距离或与有PD的地点的估计水接触来计算感染压力（IP），并比较不同IP变体在回归模型中解释的方差量。通过使用水动力模型模拟颗粒排放来计算排放养殖场与接收养殖场之间的水接触。通过水接触估计的IP是模型中PD病例和对照的最佳预测指标，其表现明显优于通过航道距离或欧几里得距离估计的IP。由于研究区域内PD的传播用水动力模型模拟的水流速度解释最为合理，我们得出结论，PD很可能是由SAV在水流中的被动漂移传播的。
