Outbreak of neuropathogenic equid herpesvirus 1 causing abortions in Yili horses of Zhaosu, North Xinjiang, China

Abstract

Background EHV-1 is one of the most serious viral pathogens that frequently cause abortion in horses around the world. However, so far, relatively little information is available on EHV-1 infections as they occur in China. In January 2021, during an abortion storm which occurred in Yili horses at the Chinese State Studs of Zhaosu (North Xinjiang, China), 43 out of 800 pregnant mares aborted. Results PCR detection revealed the presence of EHV-1 in all samples as the possible cause of all abortions, although EHV-4, EHV-2 and EHV-5 were also found to circulate in the aborted fetuses. Furthermore, the partial ORF33 sequences of the 43 EHV-1 shared 99.3–100% and 99.0–100% similarity in nucleotide and amino acid sequences respectively. These sequences not only indicated a highly conserved region but also allowed the strains to group into six clusters. In addition, based on the predicted ORF30 nucleotide sequence, it was found that all the strains carried a guanine at the 2254 nucleotide position (aspartic acid at position 752 of the viral DNA polymerase) and were, therefore, identified as neuropathogenic strains. Conclusion This study is the first one that establishes EHV-1 as the cause of abortions in Yili horses, of China. Further characterization of the ORF30 sequences revealed that all the EHV-1 strains from the study carried the neuropathogenic genotype. Totally, neuropathogenic EHV-1 infection in China’s horse population should be concerned although the virus only detected in Yili horse abortions.

Equine abortion and stillbirth in California: a review of 1,774 cases received at a diagnostic laboratory, 1990–2022

“…Despite the availability of vaccines and the implementation of good husbandry conditions, EHV1 continues to be one of the most commonly reported causes of equine abortion worldwide. 7,14,15,18,26 In our study, information about the vaccination status of the dam was not available in most cases.…”

Neuropathogenic Equid Herpesvirus 1 involving in horse respiratory disease outbreak, north Xinjiang, China, 2021-2023

“…however, in our country, only four papers published in 2016, and 2022 showed that EHV-1 had been found in aborted fetal lung tissue of mares. Of these studies, three researches revealed that EHV-1 was responsible for abortion of Yili horses from the Chinese State Studs in Zhaosu county, 2015 [5], and 2021 [7,16], respectively.one research reported that the virus was detected in aborted samples of Przewalski's horse conservation center in Jimusaer county, 2019 [17]. until now, there is no information on EHV-1 involving in respiratory problem of horses, China.…”

“…The presence of EHV-1 DNA in these nucleic acid samples was subsequently detected by TaqMan-MGB qPCR by targeting partial ORF68 genes, primers and probe in Table S1. For the qPCR, SuperReal PreMix (Tiangen Biotech Co.) was used to amplify the target genes under the following conditions: an initial denaturation at 95°C for 15 min, followed by 45 cycles, each with a denaturation step at 94°C 30 s, an annealing and an extension steps at 60°C 30 s. EHV-2 (716 nt), EHV-4 (587 nt) and EHV-5 (881 nt) DNA in these nucleic acid samples was subsequently detected by PCR by targeting partial ORF33 (EHV-4) or ORF8 (EHV-5 or EHV-2) genes (encoding the gB) as previous published studies [7,16,24].…”

“…Then the inoculum was discarded and DMEM containing 2% fetal bovine serum (FBS) was added. After incubation for 72 h, the cell cultures were harvested through three times of freezing and thawing and subsequently inoculated into cells for another six passages, and the cytopathic effects (CPEs) were monitored daily after inoculation, the cell cultures were ampli ed for full ORF33 gene, and partial ORF30 of EHV-1 by PCR as reported in recent researches [7,16]. Positive PCR amplicons were then ligated into a pESI-T vector (Yeasen Biotech) for transforming E. coli DH5α Chemically Competent Cell (Weidi Biotech) and three clones of each amplicon were eventually selected for Sanger sequencing (Sangon Biotech).…”

“…EHV-1 genome is 150 kbp and encodes up to 80 open reading frames (ORFs) [20][21][22]. Among these, ORF30 encodes the viral DNA polymerase, a single point mutation, whether an adenine (A), guanine (G) or cytosine (C) is present at position 2254 respectively, which is strongly but not exclusively associated with both non-neuropathogenic or neuropathogenic EHV-1 [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Similarly, ORF33 encoded the conserved envelope glycoprotein B (gB), which is frequently targeted for detection and phylogenetic analyses [6,16,[20][21][22].…”