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.

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Background: Nine species of Equus caballus papillomavirus (EcPV) have been reported to infect horses, however, there are so far no reports of such infections in China. Results: In our pioneer study with Chinese horses, we found EcPV-1 in intranasal papilloma and nasal swabs, EcPV-2 in nasal swabs and semen, and EcPV-7 primarily in semen. This indicates that EcPVs are indeed hosted by horses in China, and that EcPV-2 and 7 may be getting transmitted though breeding. Sequence analyses for complete genomic sequences of EcPV-1 (G2), EcPV-2 (XJ-KS1391) and EcPV-7 (XJ-zs1) were performed which indicated that EcPV-1, 2 and 7, that infect horses in China, share 99.3% nt identity with the already published sequences for EcPV-1, 2 and 7. These observations indicate that three types of EcPVs identified in the current study are highly similar variants of previously known types of EcPV-1, 2 and 7. Phylogenetic analysis based on L1 genes in GenBank showed that EcPV-1, 2 and 7, found in Chinese horses, are closely related to and clustered together with already known EcPV-1, 2 and 7, respectively. Conclusion: Our study provides a novel evidence for EcPVs infection and circulation in Chinese horses and thus lays the foundation for a systematic and detailed epidemiological study of these infections in Chinese horses.

Human papillomavirus type 124 (HPV124) is a betapapillomavirus that is associated with viral warts, actinic keratosis, and squamous cell carcinoma incidence. No reports of HPV124 infection in mainland China have been reported to date. In a survey of Chinese horses, we detected HPV124 via next-generation sequencing (NGS) in nasal swabs from 4% (2/56) of thoroughbred horses, and 7% (2/30) of the Akhal-Teke horses, suggesting that horses can serve as a reservoir species for this virus. In addition, HPV124 was detected in 17/50 lung tissue samples from aborted Yili horse fetuses that were initially found to be negative for equid herpesviruses and equine arteritis virus, suggesting that this pathogen may potentially contribute to abortion incidence among horses. Further investigation showed that all workers involved in Yili mare production of farm B were positive for HPV124, while all other assessed individuals in farm B or without any history of contact with horses were negative for this virus. indicating that this HPV124 strain may be transmissible from horses to human workers at an HPV124-positive farm. Sequence analyses of E6 gene sequences from 18 Chinese HPV124 samples were performed, revealing that the 7 of 18 HPV124 strain identified among horses in the present study shared 100% sequence identity with previously published HPV124 isolate. Phylogenetic analyses based on E6 gene sequences in GenBank further revealed that the HPV124 isolate identified herein was closely related to the NJ3900 HPV124 reference strain, clustering together with the established Beta 1 HPV lineage. These results provide new evidence that HPV124 can infect Chinese horses, may function as a causative agent for abortions in Yili horses, and may also infect humans laboring in Yili mare stables.

Human papillomavirus type 124 (HPV124), a member of betapapillomavirus, is associated with viral warts, actinic keratosis, and squamous cell carcinoma incidence in human. No reports of HPV124 infection in mainland China have been reported to date. In a survey of Chinese horses, we detected HPV124 via next-generation sequencing (NGS) in nasal swabs from 42% (39/93) of Thoroughbred horses, 7% (2/30) of the Akhal-Teke horses, and 17/50 aborted fetal lung tissues of Yili mares that were initially found to be negative for equid herpesvirus 1, which indicated the virus can be trans-species infection in different breeding horses, and suggested that this pathogen may potentially contribute to abortion incidence among horses. Further investigation showed that some workers involved in horse farm were positive for HPV124, which strongly suggested that horse-origin HPV124 strain may be transmissible from human workers to horses. Sequence analyses of E6 gene sequences from 18 Chinese HPV124 samples were performed, revealing that the 7 of 18 HPV124 strain identified both horses and human in the present study shared 100% sequence identity with previously published HPV124 isolate. Phylogenetic analyses based on E6 gene sequences in GenBank further revealed that the HPV124 isolate identified herein was closely related to the NJ3900 HPV124 reference strain, clustering together with the established Beta 1 HPV lineage. These results provide first evidence that HPV124 can infect horses, may function as a causative agent for abortions in Yili horses, and come from HPV124-positive humans laboring.