Scallop introductions and transfers, from an animal health point ofview |
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| Authors: | S Mortensen |
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| Institution: | (1) Department of Aquaculture, Institute of Marine Research, PO.Box 1870, Nordnes, 5817 Bergen, Norway |
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| Abstract: | The effects of transfers and introductions of bivalue molluscs are alwaysmore or less unpredictable. Moving scallops, there is a risk of introducingpathogenic agents or of disturbing the balance between potentiallypathogenic agents and host species in the recipient ecosystem. Risk is noteliminated by merely following official regulations. Some factors which maybe important in order to assess risk, and to choose the level of risk we arewilling to accept, are:
The existence of ``stowaways', and the action of mechanical vectors.One organism may carry another, and it is seems impossible to obtain a``clean' organism, in spite of long quarantines.
The biological vector function. There may be unknown reservoirs,intermediate or alternative hosts of pathogenic agents in the ``new'environment. An introduced species may also carry potentially pathogenicagents into a new ecosystem.
The often lacking knowledge concerning epizootiology. Life cycles ofmany pathogenic agents are poorly known, as are the infectious dose ofagent, influence of environmental factors on disease, etc.
The diagnostic tools, and the ``human factor' in diagnostics. Methodsare often not sensitive enough to detect a pathogenic agent in a carrierstate, or immediately after the agent has entered the host, or at a lowprevalence/how intensity level. It is also important that personnel aresufficiently trained to do the diagnostic work.
The official priority of disease control. There are no notifiablediseases of scallops.
EC regulations, and the ``one area/one agent/one bivalve species'management.
National and international trade, including illegal transport of livebivalves.Considering these factors enables a better focus on the riskfactors and the assessment of risks associated with introductions andtransfers of scallops. Consideration may also help to clarify the scientificlevel of knowledge and experience required to handle scallop diseases, andfocus on practical problems in scallop health control. |
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| Keywords: | bivalves disease introductions and transfers risk assessment scallops |
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