18S rDNA sequences indicate that PKX organism parasitizes bryozoa

PKX, the organism which causes Proliferative Kidney Disease (PKD) in salmon id fish, has been identified as a myxozoan parasite since 1985. However, th e apparent lack of development to maturity of the spores that are produced in salmonid hosts has precluded further classification of this organism. He re we report the degree of similarity between a reference 18S rDNA sequence of PKX in the databank with sequences obtained from myxozoan parasites fou nd in several species of North American bryozoans and from PKX collected fr om bath Europe and North America. Three of the sequences from bryozoans wer e within the range of variation shown by PKX while others were slightly dif ferent. These results strongly indicate that at least some variants of myxo zoan parasites of bryozoans are PKX, and thus that Bryozoa are natural host s for PKX.