Detection of Cyprinid Herpesvirus-3 in Field Samples of Common and Koi Carp by Various Single-Round and Nested PCR Methods

Cyprinid herpesvirus-3 (CyHV-3, previously described as koi herpesvirus) is a causative agent of the lethal disease in koi and common carp that can adversely affect common and koi carp breeds. Outbreaks with mass mortality have occurred world wide since 1998. At present, several different polymerase chain reaction (PCR) tests are in use to detect CyHV-3 in koi and common carp. In this study, we compared the sensitivity of the single-round PCR assays of Gray, Gilad, and Bercovier, and further the Gilad and Bercovier-nested PCR assays by testing tissue samples with known amounts of CyHV-3 DNA and by testing the panel of field tissue samples (106) of koi and common carp. The sensitivity of all the PCR protocols used in this study was similar within testing the spiked homogenate sample with a known amount of CyHV-3 DNA (ca. 12 DNA copies), with the exception of Gray PCR (25 copies). Detection levels of the individual PCR methods in field samples varied. The single-round Bercovier method was the most sensitive in comparison with the following two single-round methods, based on the number of positive field samples (34%). The improvement of sensitivity and confirmation of specifity were sufficient when the two-round Bercovier method was used with a detection of 44.3% of positive samples in total.