Production and shedding of channel catfish virus (CCV) and thymidine kinase negative CCV in immersion exposed channel catfish fingerlings

Abstract

The progression of channel catfish virus (CCV) and thymidine kinase negative recombinant CCV (CCVTK) infections in immersion challenged channel catfish Ictalurus punctatus fingerlings was studied by plaque assay and quantitative polymerase chain reaction (QT-PCR). Infectious CCV was isolated from Day 2 through Day 8 in skin and blood and through Day 10 PI in posterior kidney and gills. Infections CCVTK was detected from Day 2 through Day 6 PI in skin and blood and through Day 8 PI in posterior kidney and gills. The kinetics of both infections were similar until Day 5 PI, after which virus concentrations were higher in CCV infected fish than in those exposed to CCVTK . Both viruses were detected in water; however, the CCV concentration was higher than CCVTK during all time periods and was detected on Days 2 through 5 PI, whereas CCVTK was detected on Days 3 through 5 PI. The QT-PCR showed higher amounts of viral DNA in the skin and water at early and late periods in infection in CCV challenged groups as opposed to CCVTK groups. This study indicates that the kinetics of CCV and CCVTK infections are similar but CCVTK infections do not persist as long and have reduced shedding ability.