MARINE ANEMIA IN FARMED CHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA) - DEVELOPMENT OF A WORKING CASE-DEFINITION

Marine anemia (plasmacytoid leukemia) is a histologically defined synd rome affecting farmed chinook salmon (Oncorhynchus tshawytscha) in Bri tish Columbia, Canada, Although the disease has received recent attent ion and has been diagnosed in many fish farms, past criteria for diagn osis have limited the depth and breadth of epidemiological investigati ons, By identifying a repeatably diagnosable subset of signs and sympt oms of affected fish, a new working case definition of marine anemia w as developed. This definition relied exclusively on histological featu res to achieve the diagnosis. The intra-observer repeatability of diag noses using the new definition was high (kappa = 0.84). An algorithm e mploying gross pathological signs was created for field investigation of the disease. The algorithm was capable of predicting histological d iagnosis with a reasonable level of accuracy, and was judged to be a v aluable tool for diagnostic decisions. We concluded that by using the case definition created in this study together with the algorithm, the comparability and accuracy of clinical and epidemiological research o f marine anemia could be improved.