Network models of live fish movements and disease spread in Scottish aquaculture

• Main Author: Werkman, Marleen
• Other Authors: Turnbull, James F., Green, Darren M, Murray, Sandy G., Marine Scotland Science
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Stirling 2012
• Subjects: Epidemiology; Aquaculture; Live fish movements; Disease spread; Salmon industry Scotland; Fishes Diseases; Norway; Atlantic salmon; Salmo salar
• Online Access: http://hdl.handle.net/1893/6510; http://dspace.stir.ac.uk/bitstream/1893/6510/1/Network%20models%20of%20live%20fish%20movements%20and%20disease%20spread%20in%20Scottish%20aquaculture_FINAL.pdf

The Scottish salmon industry is facing challenges in the control of aquatic infectious disease, as is the case in other countries such as Chile and Norway. Disease outbreaks can have an enormous economic impact and possibly affect wild fish populations. Disease transmission in an aquatic environment is complex and there are several transmission routes (vertical transmission, natural reservoirs, hydrodynamic transmission and long-distance movements). Effective control methods such as vaccines are not available in all cases and therefore disease prevention remains a priority. In livestock, epidemiological network models have been proven to be a highly useful tool to investigate the role of different transmission routes on the course of epidemics and have the potential to provide the same utility for aquatic networks. Understanding the complex contact network will result in more effective disease prevention, surveillance systems and control strategies. The aim of this thesis was to investigate the Scottish live fish movement network and its consequences for pathogen transmission between farms in order to develop and optimize control strategies for epidemics. The main objective of chapter 3 was to investigate the effect of different fallowing strategies on the spread of diseases with different transmission properties. A network model was constructed that included both local transmission and long-distance transmission. The basic structure of this network was a ring model where neighbours within a management area could infect each other and non-local transmission occurred at random. The results showed that when long-distance transmission was under reasonable control in comparison with local transmission risk, synchronized fallowing at the management area level was potentially a highly effective tool in the control of infectious diseases. Chapter 4 presents a detailed description of the number of live fish movements and their timing for Atlantic salmon (Salmo salar) in Scottish aquaculture. For this, movement records ...