Introduction of the family Alloherpesviridae: The first molecular detection of herpesviruses of cyprinid fish in Hungary

The taxonomy of herpesviruses has been changed recently radically. In 2008, a new order, the Herpesvirales was established to contain the family Herpesviridae along with two additional new families, Alloherpesviridae and Malacoherpesviridae. The family Alloherpesviridae includes the herpesviruses isolated from amphibians and fish, whereas Malacoherpesviridae contains the single herpesvirus originating from an invertebrate host, namely an oyster. Previously, these viruses had been classified into the family Herpesviridae based on their characteristic morphology, although they did not fit unambiguously into any genus or subfamily of the family. The newly established family Alloherpesviridae is now officially divided into four genera. One of these contains the herpesviruses of amphibians, whereas the other three contain those of different fishes. The genus Cyprinivirus includes three virus species originating from cyprinid fishes. Cyprinid herpesvirus 1 (CyHV-1) is the causative agent of the so called carp pox that occurs commonly also in Hungary. CyHV-2 was isolated from goldfish (Carassius auratus) first in Japan, but later it was detected on almost every continent. CyHV-3 is the official taxonomical name for the so called koi herpesvirus that causes devastating losses to the carp and ornamental carp breeders worldwide. In the present work, the authors report the first PCR-based detection of CyHV-1 és 2 in Hungary. For the very first time, the occurrence of CyHV-2 is described in the Prussian carp (Carassius gibelio) instead of the usual host, the goldfish. A 464 base-pair-long fragment of the DNA-dependent DNA polymerase gene was amplified by PCR from both viruses. The nucleotide sequence of the amplicons was determined and analyzed. In the case of both viruses, the nucleotide sequences exhibited only slight (1%) discrepancies when compared to their counterparts published abroad previously. However, none of these differences resulted in alterations of the amino acid sequences.