First detection and genetic characterization of equid herpesvirus 2, 4, and 5 in China

Detection and genetic characterization of equine viruses in Sweden using viral metagenomics

BACKGROUND

Viral infections pose a significant challenge to the equine population, compromising welfare and causing substantial economic losses for the global equine industry. While numerous equine viral pathogens have been identified, many suspected viral infections remain undiagnosed. This highlights the need for further identification and characterization of viruses circulating within the equine population. In this study, we utilized viral metagenomics to investigate viruses present in serum samples and nasal swabs collected from horses in Sweden. The primary focus was on horses presenting with fever, although control horses were also included for comparison.

RESULT

The viral metagenomic analysis identified several viruses in the investigated samples. Among nasal swabs, the majority of the viral reads were classified as various equine herpesvirues (EHVs), mainly EHV-2 and EHV-5. Other viruses in nasal swabs include but are not limited to EHV-4, Torque teno equus virus 1 (TTeqV1) and equine copiparvovirus (eqCopV). Both TTeqV1 and eqCopV were also detected in the serum samples together with equine circovirus and equine pegivirus. A number of the detected viruses were further genetically characterized and were shown to display high sequence similarity to viruses from the US and/or China. qPCR screening of a selected number of the detected viruses revealed a rather low detection rate (1.6%-9.4%) in individual horses.

CONCLUSION

This study identified several viruses that circulate in the horse population in Sweden, some of which have not been previously detected in Sweden or Europe. Furthermore, the complete or nearly complete genomes of several of these viruses have been genetically characterized. These new data provide a valuable foundation for developing improved detection assays and conducting larger prevalence studies to assess the potential impact of these viruses on the equine population. Such efforts could ultimately contribute to enhanced equine welfare.

Identification of neuropathogenic Varicellovirus equidalpha1 as a potential cause of respiratory disease outbreaks among horses in North Xinjiang, China, from 2021-2023

BACKGROUND

Varicellovirus equidalpha1 (formerly Equid alphaherpesvirus 1, EqAHV-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 EqAHV-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 EqAHV-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 EqAHV-2, EqAHV-4, and EqAHV-5. In total, three EqAHV-1 strains responsible for causing respiratory illness in horses were isolated successfully, and full-length ORF33 sequence comparisonsand phylogenetic analyses indicated that these isolates may have originated from EqAHV-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 EqAHV-1. ORF30 sequence characterization revealed that these EqAHV-1 strains harbored a neuropathogenic genotype. Given the detection of this virus in horses suffering from respiratory disease, concern is warranted with respect to this neuropathogenic EqAHV-1 outbreak.

Molecular detection of equid herpesvirus in bronchoalveolar lavage fluid from asymptomatic horses in Southern Brazil

Background and Aim

Molecular approaches to diagnose respiratory viruses have provided an opportunity for early and subclinical pathogen detection, particularly in samples from the upper respiratory tract. This study aimed to investigate the presence of herpesviruses, particularly equid herpesvirus (EHV)-2 and EHV-5, in samples from the lower respiratory tract of healthy racehorses from Southern Brazil.

Materials and Methods

Samples from the lower respiratory tract (i.e., bronchoalveolar lavage fluid [BALF]) were assessed by video endoscopy, cytological evaluation of BALF, and tracheal aspirates (TA), along with quantitative polymerase chain reaction (qPCR), to detect equine herpesvirus infection in the lower respiratory tract samples and compare corresponding cytological and endoscopic findings.

Results

At least one abnormality per horse during endoscopy examination was observed, including, but not limited to, mucous secretion in the airways and pharyngeal lymphoid hyperplasia. The presence of EHV-2 and/or EHV-5 was detected by qPCR in 3/10 animals. One horse was positive for EHV-2 alone, one for EHV-5 alone, and one for both.

Conclusion

To the authors' knowledge, this is the first molecular detection of EHV-2 and EHV-5 in Brazilian thoroughbred horses. These findings may provide new insights into the epidemiology of EHV-2 and EHV-5 in Brazilian horses, evidencing the importance of the molecular investigation, early detection, and prevention of respiratory diseases.

Epidemiological and Phylogeographic Study of Equid Herpesviruses in Tunisia

Equid herpesvirus (EHV) is a contagious viral disease affecting horses, causing illness characterized by respiratory symptoms, abortion and neurological disorders. It is common worldwide and causes severe economic losses to the equine industry. The present study was aimed at investigating the incidence of EHVs, the genetic characterization of Tunisian isolates and a spatiotemporal study, using 298 collected samples from diseased and clinically healthy horses. The global incidence of EHV infection was found to be about 71.81%. EHV2 and EHV5 were detected in 146 (48.99%) and 159 (53.35%) sampled horses, respectively. EHV1 was detected in 11 samples (3.69%); EHV4 was not detected. Co-infections with EHV1-EHV2, EHV1-EHV5 and EHV2-EHV5 were observed in 0.33%, 1.34% and 31.54% of tested horses, respectively. Phylogenetic analyses showed that gB of EHV2 and EHV5 displays high genetic diversity with a nucleotide sequence identity ranging from 88 to 100% for EHV2 and 97.5 to 100% for EHV5. Phylogeography suggested Iceland and USA as the most likely countries of origin of the Tunisian EHV2 and EHV5 isolates. These viruses detected in Tunisia seemed to be introduced in the 2000s. This first epidemiological and phylogeographic study is important for better knowledge of the evolution of equid herpesvirus infections in Tunisia.

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

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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03171-1.