Genetic relationships among herpes-like viruses isolated from sturgeon

We report the identification of partial DNA polymerase gene sequences of seven herpes-like viruses found in sturgeon Acipenser spp. from North America and Europe. Phenetic comparisons using nucleic acid and deduced protein alignments divided the sturgeon herpes-like viruses into three genogroups. The first genogroup includes the previously described Acipenserid herpesvirus I (AciHV-1) and two new isolates from farmed white sturgeon A. transmontanus from California and wild white sturgeon from Idaho. The second genogroup contains the previously described Acipenserid herpesvirus 2 (AciHV-2) and a new isolate from wild white sturgeon found in Oregon. The third genogroup includes two viruses with identical amino acid sequences found in farmed white sturgeon from Italy and Canada. We propose to name the third sturgeon herpes-like genogroup Acipenserid herpesvirus 3 (AciHV-3). The phylogram used for comparing the relationships of these viruses shows strong bootstrap support (82%) for two separate clades among the sturgeon herpes-like viruses. One clade includes all the AciHV-1 isolates, whereas the other clade is divided into subclades. Interestingly, the subclade containing AciHV-2 branches outside the sister relationship between Ictalurid herpesvirus I and AciHV-3. An examination of the genogroups indicates that a prior hypothesis that AciHV-2 may have rapidly evolved from AciHV-1 is unlikely; instead, we suggest that AciHV-2 represents a more recent introduction of a new strain of virus to sturgeon farms in California. Lastly. the phylogenetic comparisons strongly suggest a pattern of spatial separation and independent evolution of the herpes-like viral genogroups found in sturgeon.