Abstract
Equid herpesvirus 5 (EHV-5) is one of two γ-herpesviruses that commonly infect horses worldwide. The objective of the study was to estimate the genetic variability within EHV-5 viruses circulating among horses in Poland. Partial glycoprotein B (gB) sequences from 92 Polish horses from 13 studs throughout Poland were compared to each other and to three EHV-5 sequences from other countries. Despite the overall high level of conservation, considerable variability was observed around the putative furin cleavage site. Based on phylogenetic analysis, the viruses clustered within two major lineages (A and B), with further sub-clustering within group A. The clustering of EHV-5 sequences was independent of age or geographical origin of the sampled horses. Recombination was identified as one of the factors contributing to the genomic heterogeneity. Viruses from unweaned foals were more similar to viruses from other foals at the same stud than to viruses form their dams, suggesting the horizontal transfer and/or evolution of EHV-5 within individual hosts. Our data indicate that the gB sequence is not suitable for tracking the source of EHV-5 infection. Further research is needed to elucidate the importance of the sequence variability around the EHV-5 gB furin cleavage site on the biology of the virus.
Highlights
Horses are natural hosts to five herpesviruses, including equid herpesvirus (EHV) type 5 [1]
We have presented the largest and the most comprehensive study of variability between Equid herpesvirus 5 (EHV-5) glycoprotein B (gB) sequences
The clustering did not appear to correlate with the geographical origin of the virus or the age of horses, as samples from different studs and horses from different age groups were distributed throughout the phylogenetic tree or haplotype network
Summary
Horses are natural hosts to five herpesviruses, including equid herpesvirus (EHV) type 5 [1] This virus is classified in the family Herpesviridae, subfamily Gammaherpesvirinae, and genus Percavirus [2]. It shares sequence similarity with another equine gammaherpesvirus EHV-2, as well as with human herpesvirus 4 (Epstein–Barr virus, EBV) [3]. It has been detected from horses worldwide with the higher frequency of detection in young horses compared to older ones [4,5,6]. The most serious, albeit rare, disease that has been linked to EHV-5 infection in mature horses is equine multinodular pulmonary fibrosis [10,11]
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