Department of Health Surveillance, Norwegian Veterinary Institute, Ullevålsveien 68, Oslo, Norway.
Prev Vet Med. 2013 Apr 1;109(1-2):136-43. doi: 10.1016/j.prevetmed.2012.08.012. Epub 2012 Sep 5.
Heart and skeletal muscle inflammation (HSMI) is an infectious disease causing losses to the Norwegian salmon farming industry due to increased mortality and high morbidity in infected salmon. The disease is listed as a notifiable disease on list 3 (national list) by the Norwegian Food Safety Authority. HSMI is believed to be a viral disease, but the association to the recently discovered Piscine reovirus (PRV) remains unclear. Undoubtedly, other factors interact to determine whether PRV-infected fish develop disease or not. In this study, logistic regression was used to model the risk of an outbreak of HSMI at the cohort level, by including spatio-temporal risk factors. The data consisted of fish cohorts grown on geo-referenced farms from 2002 to 2010. The risk factors included were: infection pressure, cohort size (maximum number of fish), cohort index (smolt characteristics), cohort lifespan (months in sea) and a geo-index calculated as the position along a local polynomial regression line based on the longitude and latitude of each farm included in the study. The results showed that the risk of developing HSMI increased with increasing cohort lifespan, increasing infection pressure and increasing cohort size, and was mostly low for cohorts grown on farms in Southern-Norway, high for farms in Mid-Norway and variable for farms in Northern-Norway (based on the geo-index). The final model was used to explore three different scenarios with regards to the risk of developing HSMI, and to calculate the probability for each cohort of developing HSMI, independent of their actual disease-status. The model suggested that the probability of developing HSMI was much higher in Mid-Norway than in the rest of the country. Even though PRV seems to be widely distributed in the environment, the finding that infection pressure has a large influence on the probability of developing HSMI, suggests that it might be possible to reduce the number of clinical outbreaks, if measures are taken to reduce infection pressure. However, the prospects of controlling the spread of HSMI and reducing clinical outbreaks might be difficult because of indications of large distance spread of the disease.
心肌和骨骼肌炎症（HSMI）是一种传染病，会导致挪威三文鱼养殖业遭受损失，因为感染三文鱼的死亡率和高发病率增加。该疾病被挪威食品安全局列为清单 3（国家清单）中的法定报告疾病。HSMI 被认为是一种病毒性疾病，但与最近发现的鱼类虹彩病毒（PRV）的关联尚不清楚。毫无疑问，其他因素相互作用决定了 PRV 感染的鱼类是否会发病。在这项研究中，逻辑回归模型用于在队列水平上对 HSMI 爆发的风险进行建模，包括时空风险因素。数据包括 2002 年至 2010 年在地理参考农场养殖的鱼类队列。纳入的风险因素包括：感染压力、队列规模（最大鱼类数量）、队列指数（幼鱼特征）、队列寿命（海上月数）和基于每个研究农场的经度和纬度计算的地理指数。结果表明，随着队列寿命的增加、感染压力的增加和队列规模的增加，HSMI 发病风险增加，而在挪威南部的农场中，队列的发病风险大多较低，在挪威中部的农场中较高，在挪威北部的农场中则变化较大（基于地理指数）。最终模型用于探讨三种不同的 HSMI 发病风险情景，并计算每个队列发生 HSMI 的概率，而不考虑其实际疾病状况。该模型表明，在挪威中部，HSMI 的发病风险远高于该国其他地区。尽管 PRV 似乎在环境中广泛分布，但感染压力对 HSMI 发病概率有很大影响的发现表明，如果采取措施降低感染压力，可能会减少临床爆发的数量。然而，控制 HSMI 传播和减少临床爆发的前景可能很困难，因为有迹象表明该疾病的远距离传播。
