Institute of Aquaculture, University of Stirling, Stirling, FK9 4LA, UK.
Prev Vet Med. 2011 Jan 1;98(1):64-73. doi: 10.1016/j.prevetmed.2010.10.004. Epub 2010 Nov 1.
Salmon production is an important industry in Scotland, with an estimated retail value >£1 billion. However, this salmon industry can be threatened by the invasion and spread of diseases. To reduce this risk, the industry is divided into management areas that are physically separated from each other. Pathogens can spread between farms by local processes such as water movement or by long-distance processes such as live fish movements. Here, network modelling was used to investigate the importance of transmission routes at these two scales. We used different disease transmission rates (β), where infected farms had the probability of 0.10, 0.25 or 0.50 per month to infect each contacted farm. Interacting farms were modelled in such a way that neighbours within a management area could infect each other, resulting in two contacts per farm per month. In addition, non-local transmission occurred at random. Salmon are input to marine sites where they are raised to harvest size, the site is then fallowed; in the model the effects of different fallowing strategies (synchronised, partial synchronised and unsynchronised fallowing at the management area level) on the emergence of diseases were investigated. Synchronised fallowing was highly effective at eradicating epidemics when transmission rate is low (β=0.10) even when long distance contacts were fairly common (up to 1.5farm(-1)month(-1)). However for higher transmission rates, long distance contacts have to be kept at much lower levels (0.15contactsmonth(-1) where β=0.25) when synchronised fallowing was applied. If fallowing was partially synchronised or unsynchronised then low rates of long-distance contact are required (0.75 or 0.15farm(-1)month(-1)) even if β=0.10. These results demonstrate the potential benefits of having epidemiologically isolated management areas and applying synchronised fallowing.
苏格兰的鲑鱼养殖业是一个重要的产业，其零售价值估计超过 10 亿英镑。然而，该鲑鱼产业可能受到疾病的入侵和传播的威胁。为了降低这种风险，该产业被划分为相互隔离的管理区域。病原体可以通过当地的水运动或远距离的活鱼运动等过程在养殖场之间传播。在这里，网络建模被用于研究这两个尺度上的传播途径的重要性。我们使用了不同的疾病传播率（β），其中受感染的养殖场每月感染每个接触养殖场的概率为 0.10、0.25 或 0.50。相互作用的养殖场以这样的方式建模，即管理区域内的邻居可以相互感染，导致每个养殖场每月有两次接触。此外，非本地传播是随机发生的。鲑鱼被输入到海洋养殖场，在那里它们被饲养到收获的大小，然后该养殖场被休耕；在模型中，研究了不同休耕策略（管理区域水平的同步、部分同步和非同步休耕）对疾病出现的影响。当传播率较低（β=0.10）时，同步休耕对根除疫情非常有效，即使远距离接触相当常见（高达 1.5 个养殖场/月）。然而，对于更高的传播率，当应用同步休耕时，必须将远距离接触保持在低得多的水平（β=0.25 时为 0.15 个接触/月）。如果休耕是部分同步或非同步的，则即使β=0.10，也需要较低的远距离接触率（0.75 或 0.15 个养殖场/月）。这些结果表明，拥有具有流行病学隔离的管理区域并应用同步休耕具有潜在的好处。
