The major diseases that afflict channel catfish have been described. The only virus disease diagnosed is the channel catfish virus disease (CCVD), which may cause large losses of fingerlings in a short time. Like mostviral diseases, the only known means of eliminating CCVD is by the destruction of all brood stock associated with the epizootic. Haemorrhagic septicaemia and columnaris disease are important bacterial diseases of catfish that cause considerable mortality. A variety of protozoan diseases also infect the species, of which ichthyophthiriasis or ‘ich’ is the most important. Eradication of the parasite is possible only during its free-swimming stages and repeated treatments over a period of days or weeks are needed to eradicate all. Costiasis is another common protozoan infection, which causes high levels of mortality, especially among fingerlings.
Various species of the external parasite Tri-chodina affect channel catfish. They occur onthe body, fins and gills. Trichodiniasis is characterized by the appearance of irregular white blotches on the head and dorsal surface of infected fish. There may also be fraying of the fins and loss of appetite. Epidermal necrosis and excessive production of mucus may occur. Dips in 30ppt salt water, a 1:500 solution of acetic acid or a 1:4000 solution of formalin form the usual treatment.
Myxosporidian parasites of the genus Henneguya, monogenetic trematode Gyrodactylus and the copepod parasites Ergasilus, Argulus and Lernaea can cause mortality among catfish.