MEDICAL-MANAGEMENT OF CHANNEL CATFISH .1. TYPES OF SKIN AND GILL PATHOGENS

Channel catfish are grown in many parts of the United States and are t he country's most important aquaculture crop; in 1991, production exce eded 181 million kilograms (398 million pounds). Although many disease s of fish have dermatologic manifestations, this presentation focuses on the organisms that attack the epithelium of the skin or gills as th e primary target organ. These pathogens include protozoa, monogenea, f ungi, and bacteria; many are ubiquitous in the aquatic environment and only cause disease if the host is immunocompromised or environmental conditions favor massive multiplication of pathogens. Ichthyophthirius multifiliis is a ciliated protozoan that is unique in that it is an o bligate parasite and is capable of massive reproduction independent of water quality; control strategies mandate multiple treatment applicat ions.