Abstract

Proliferative kidney disease (PKD) is one of the most economically important diseases among commercially reared rainbow trout (Oncorhynchus mykiss) in Europe and causes significant losses among Pacific salmon and rainbow trout populations in western North America. The parasite that causes PKD is a poorly understood myxosporean (PKX), presumed but not yet proven to be a member of the family Sphaerosporidae, genus Sphaerospora. The disease occurs in both cultured and feral populations of salmonids that come into contact with a 20-25 mu m waterborne infective stage. The disease is often seasonally dependent occurring at water temperatures above 15 degree C in the summer and fall months of the year. No vaccines have yet been developed to control PKD, and only recently have experimental therapies been applied. Both fumagillin DCH, an antibiotic effective against certain microsporidia and myxosporidia, and the arylmethane dye malachite green, have shown some promise as treatments for PKD. Unfortunately, neither drug is licensed for use in the U.S. and both treatments suffer from potential difficulties with drug toxicity, tissue residues, or drug discharges in hatchery effluent waters. (DBO)