Moran et al. (1999) listed some 45 species of Kudoa, and about 10 species have been described since. Most species of Kudoa are recognized for their impacts on the marketability of their commercially important fish hosts, as opposed to causing mortality. Unlike most other members of Kudoa (and myxozoans in general), K. thyrsites has broad host specificity.
The parasite is known to infect the muscle of over 30 different hosts from several families of marine fishes around the world. Species familiar to people in BC include sea trout, herring, hake, wild and farmed salmon— both Atlantic and Pacific species - North Pacific arrow tooth flounder, mahi mahi. Other fish species found to be susceptible are Dover sole and Pacific halibut. K. thyrsites infection can result in substantial economic losses to the finfish aquaculture industry as infected fish have no signs of disease.
After death of an infected fish however, severe flesh deterioration occurs due to proteolytic (digestion of protein) digestion of the muscle tissue. At low levels of infection the pathology of K. thyrsites infection can go unnoticed in commercially sold fish, but at higher levels of infection the proteolytic activity of the parasite produces extensive myoliquefaction (dissolution or liquefaction of muscular tissue) and the fish meat is no longer viable commercially. Husbandry methods that prevent or minimize exposure to K. thyrsites are also unavailable due to limited life-history knowledge of the parasite. For instance, complete life-cycles are yet undetermined for any member of the genus. Understanding how fish become infected will be vital for conducting empirical trials to understand infection dynamics and to evaluate husbandry methods.
The BC Centre for Aquatic Health Sciences Society (BC CAHS) has been retained by Marine Harvest Canada to develop strategies to understand and mitigate the effects related to Kudoa thyrsites infection in Atlantic salmon (Salmo salar).
The Kudoa Mitigation Initiative Project aims to accomplish the following objectives:
Moran, J.D.W., D.J. Whitaker, M.L. Kent. 1999. A review of myxosporean genus Kudoa Meglistch, 1947, and its impact on the international aquaculture industry commercial fisheries. Aquaculture 172:163-196.