Research Document - 2010/018
Pathway of effects between wild and farmed finfish and shellfish in Canada: Potential factors and interactions impacting the bi-directional transmission of pathogens
By Amelia A.M. Grant and Simon R.M. Jones
Abstract
This paper documents the evidence in support of linkages proposed among activities, stressors and effects as they relate to the release of pathogens from aquaculture. The extent to which pathogens released from aquaculture sites are stressors requires knowledge of infection and disease in wild aquatic populations. In Canada and other jurisdictions, targeted surveillance of endemic diseases should be established. Without this knowledge an assessment of whether and to what extent pathogens are stressors cannot be made. There is scientific evidence that pathogens present in wild populations are the source of initial infections in aquaculture animals and some evidence that aquaculture animals release pathogens to their environment. However evidence of pathogen transfer from aquaculture animals and/or products to wild populations is very limited. This paper provides a background to the general principles of pathogen transfer: factors related to the host, pathogen and environment are known to form complex interactions which together influence pathogen transmission and subsequent disease development. The paper also emphasises the distinction between infection and disease. These principles are discussed using four significant aquatic pathogens that exemplify specific modes of biology or transmission among bivalves or finfish: infectious salmon anaemia virus, Renibacterium salmoninarum, Haplosporidium nelsoni, and Aeromonas salmonicida. Gaps in knowledge and some recommendations for future study are also discussed.
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