Protozoan ciliate. Very contagious, infects most species of marine fish. Parasite can remain dormant for long periods of time subeptitelially, often breaking out into the reproductive phase only when fish are stressed.
Disease is seldom fatal quickly, giving time for diagnosis and successful treatment. In dormant stage causes no problems. Possibly many fish carry the parasites, without notice or harm.
In hatcheries & closed systems use regular quarantine procedures to prevent outbreaks. In Aquaculture in sea cages try to site cages in waters where the parasite is not prevalent.
Taxonomic affinities of Cryptocaryon irritans and Ichthyophthirius multifiliis
inferred from ribosomal RNA sequence data
From Diseases of Aquatic Organisms Volume 22: 39-43, 1995
B. K. Diggles, R. D. Adlard Department of Parasitology. The University of Queensland
Dr. Burgess, Peter
Aquarium Sciences & Conservation
Brentwood Essex UK