Epizootiology of Channel Catfish Virus Disease

Channel catfish virus disease (CCVD) is a highly pathogenic herpesvirus disease of cultured channel catfish, Ictalurus punctatus, fry and fingerlings. The disease is confined to the southern United States, but occurs sporadically in other areas where young channel catfish are intensively cultured. Blue catfish, I. furcatus, have been experimentally infected with CCV, but other ictalurids appear to be refractory. The causative virus can be isolated only from fish showing clinical signs and morbidity. The clinical signs resemble those of other fish viral diseases. Histopathology is characterized by hemorrhage, necrosis, and edema in most tissues. It is possible to isolate CCV in brown bUllhead, I. nebulosis, cells or cell cultures derived from channel catfish ovaries. The immunological response of channel catfish is discussed and theoretical control measures are suggested. fected fish may influence the rate of mortality and may serve as triggering mechanisms for epizootics. Optimum water temperature for CCVD is above 25°C. Mortality may occur at 20°C, but below this temperature the effects of CCV are diminished. Secondary bacterial infections of Aeromonas hydrophila and Flexibacter columnaris also serve as synergistic forces in CCV infections and probably contribute to mortality.