Definitions of Category

Each disease agent of shellfish has been assigned to a Category with respect to current shellfish health conditions in Canada. The Category was assigned according to the following definitions:

Category 1

Agents of infectious diseases which have not been detected in Canada, but the shellfish host species of which are found in Canada. Because these diseases can have serious impact on shellfish stocks, the disease agents responsible must be kept out of Canada.

Category 2

Agents of infectious diseases which have a limited geographic distribution within Canada. Because these diseases can have serious impact on shellfish health, these agents must be prevented from spreading to regions or provinces where they are not known to occur. Importation of shellfish between regions or provinces must be guided by the principle that the importation will not result in the introduction of a disease agent not already known to occur in the receiving region or province.

Category 3

Agents of infectious diseases whose host species do not presently occur in Canada. When similar agents are listed for host species already present in Canadian waters, these agents are not assumed to be identical to those present in the non-indigenous hosts. Therefore, if a host for a Category 3 disease agent is discovered in or becomes introduced into Canada, the disease agent automatically will be moved to Category 1 status.

Category 4

Agents of infectious diseases which have negligible or questionable significance in Canada because:

  1. they cause no significant pathology or,
  2. the pathological condition is related to husbandry.

Detection of a Category 4 disease agent does not imply restriction on importation into Canada or on movement within Canada.

Citation Information

Bower, S.M., McGladdery, S.E. (2014): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Definitions of Category

Date last revised: June 1997
Comments to Susan Bower

Date modified: