Equid herpesvirus 8: Complete genome sequence and association with abortion in mares.
Authors: Garvey Marie, Suárez Nicolás M, Kerr Karen, Hector Ralph, Moloney-Quinn Laura, Arkins Sean, Davison Andrew J, Cullinane Ann
Journal: PloS one
Summary
# Editorial Summary: Equid Herpesvirus 8 and Reproductive Disease in Horses Until recently, equid herpesvirus 8 (EHV-8) was considered a minor pathogen associated primarily with respiratory disease in donkeys and horses in limited geographic regions; however, this Irish study has identified a concerning new clinical presentation—abortion in mares—that was initially mistaken for EHV-1 infection. Researchers sequenced the complete genomes of four EHV-8 strains isolated between 2003 and 2015 using Illumina technology, including two from aborted equine fetuses and two from affected donkeys, revealing greater than 98.4% nucleotide identity across strains and demonstrating that genomic variation is host-independent rather than linked to clinical manifestation. Two key findings emerge: EHV-8 demonstrates phylogenetic proximity to EHV-9 (not EHV-1), with 24 of 76 predicted proteins completely conserved across Irish isolates, and the virus's association with abortion represents a previously unrecognised pathogenic capability that warrants diagnostic vigilance. The data suggest that donkeys may serve as asymptomatic or minimally symptomatic reservoir hosts, presenting a biosecurity concern for equine operations with mixed-species populations. Given EHV-8's capacity to cause reproductive failure whilst evading initial diagnostic protocols designed for EHV-1, practitioners should maintain heightened awareness during abortion investigations and consider EHV-8 in differential diagnoses, particularly where serological or molecular testing for traditional herpesvirus culprits yields unexpected results.
Read the full abstract on PubMed
Practical Takeaways
- •EHV-8 should be considered in differential diagnosis of equine abortion cases, as it has been misidentified as EHV-1 in clinical practice
- •Donkeys may harbour and transmit EHV-8 to horses; biosecurity protocols should account for this potential cross-species transmission risk
- •Molecular diagnostic confirmation is essential for EHV-8 identification, as it cannot be reliably distinguished from EHV-1 by clinical presentation alone
Key Findings
- •Complete genome sequences of four EHV-8 strains from Ireland (2003-2015) show >98.4% nucleotide identity regardless of host species
- •Two EHV-8 strains were isolated from cases of abortion in horses, previously misdiagnosed as EHV-1
- •EHV-8 is phylogenetically closer to EHV-9 than to EHV-1, with 24 of 76 predicted protein sequences completely conserved among Irish strains
- •One EHV-8 strain was isolated from a donkey with neurological disease, suggesting donkeys may serve as disease reservoirs