Scottish Marine and Freshwater Science Volume 4 Number 3: Epidemiology and Control of an Outbreak of Viral Haemorrhagic Septicaemia in Wrasse Around Shetland Commencing 2012

7 Containment Areas Around VHS Positive Sites

Containment areas comprising an inner protection zone and an outer surveillance zone were established around the six sites operating under CDN in accordance with EC Council Directive 2006/88/ EC.

Individual protection zones with a radius of 500 m were established around the five VHS positive farms. A smaller protection zone with a radius of 250 m was established around the first-reported site because there is disinfection of tank-effluent. The radius of the protection zones is supported by estimated pathogen transmission distances using a transport-epidemiology model developed by MSS ^[31] . This model calculates the time required for the abundance of a pathogen released from a point source to decrease below its minimum infectious dose and then estimates the average distance that a peak amount of the pathogen travels over this time. Further details of the model and parameter values used are presented in Appendix 1.

Surveillance zones with a perimeter set at twice the radius of the protection zones have also been established. These zones do not include any aquaculture production facilities stocking fish other than those operating under CDN. Maps illustrating the containment areas for the six sites are presented in Figure 2.

Figure 2. Containment areas around sites operating under CDN