Identification of Neuropathogenic Equid Herpesvirus 1 as a Potential Cause of Respiratory Disease Outbreaks among Horses in North Xinjiang, China, from 2021-2023

Abstract

Abstract Background: Equid herpesvirus 1 (EHV-1) is among the most important viruses responsible for respiratory disease outbreaks among horses throughout the world. No reports to date have detailed the association between EHV-1 and respiratory disease among horses in China. This study described one such outbreak among a population of horses in north Xinjiang that occurred from April 2021 - May 2023. Results: qPCR revealed that EHV-1 was detectable in all samples and this virus was identified as a possible source of respiratory disease, although a limited subset of these samples were also positive for EHV-2, EHV-4, and EHV-5. In total, three EHV-1 strains responsible for causing respiratory illness in horses were isolated successfully, and full-length ORF33 sequence comparisons and phylogenetic analyses indicated that these isolates may have originated from EHV-1 strains detected in Yili horse abortions. ORF30 sequence data additionally suggested that these strains were neuropathic, as evidenced by the presence of a guanine residue at nucleotide position 2254 corresponding to the aspartic acid present at position 752 in the DNA polymerase encoded by this virus. Conclusion: This study is the first report of an outbreak of respiratory disease among horses in China caused by EHV-1. ORF30 sequence characterization revealed that these EHV-1 strains harbored a neuropathogenic genotype. Given the detection of this virus in both aborted equine fetuses and in horses suffering from respiratory disease, concern is warranted with respect to this neuropathogenic EHV-1 outbreak.