Genetic characterization of equid herpesvirus type 1 from cases of abortion in Poland

Equid herpesvirus type 1 (EHV-1) is a common viral infection associated with varied clinical outcomes including respiratory disease, abortion and neurological disease. We have characterized EHV-1 sequences (n = 38) obtained from cases of equine abortion in Poland between 1999 and 2016, based on sequencing of PCR products from open reading frames (ORF) 30 and 68 of the EHV-1 genome. The majority (81.6%) of sequences were not classified into any of the previously described groups based on the ORF68 sequence. The remaining sequences belonged to ORF68 group III (7.9%) or IV (10.5%). A haplotype network analysis did not show any obvious structure within networks of local Polish sequences, nor within a global network of 215 EHV-1 sequences when these networks were coloured based on the geographical origin of viruses or date of detection. Our data suggest that ORF68 does not provide a reliable molecular marker for epidemiological studies of EHV-1, at least in a global sense. Its usefulness to aid local investigations of individual outbreaks remains to be established. All but two Polish EHV-1 sequences belonged to the ORF30 N₇₅₂ genotype. The two ORF30 D₇₅₂ viruses were obtained from abortion cases in 2009 and 2010. Hence, abortion cases that occurred in Poland between 1999 and 2016 were caused predominantly by EHV-1 with the ORF30 N₇₅₂ genotype, with no indication of an increase in the prevalence of the ORF30 D₇₅₂ variant.