Special Issue "Equine Viruses": Old "Friends" and New Foes?

Molecular surveillance of equine parvovirus-hepatitis from oral, nasal, vaginal, and semen specimens collected from horses living in Korea

Equine parvovirus-hepatitis (EqPV-H) is one of the etiological agents of Theiler's disease, causing fulminant hepatitis; however, its transmission route and pathogenesis remain unclear. In the present study, we aimed to determine EqPV-H shedding in oral/nasal/vaginal swabs or semen samples from horses living in Korea using nested polymerase chain reaction. We then used the data obtained to investigate various risk factors associated with EqPV-H including viral shedding, hepatopathological changes, and genetic diversity. Our data revealed occurrence of EqPV-H shedding in these animals (oral: 3/102 [2.9%]; nasal: 3/102 [2.9%]; semen: 1/9 [11.1%]) and identified that both age and country of foaling were significantly associated with EqPV-H shedding (p < .05). In addition, we noted that one of the newly isolated strains clustered separately from the other strains in the phylogenetic tree, revealing unique nucleotide and amino acid substitutions. This is a field surveillance study providing evidence of natural and venereal shedding of EqPV-H and describing its presence in both oral/nasal fluids and semen. This epidemiological and clinical analysis may help specify the clinicopathological features of EqPV-H and facilitate the development of novel disease prevention strategies.

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.

AK-2011 strain for the development of a vaccine against equine rhinopneumonitis

Equine rhinopneumonitis is an acute, highly contagious disease found virtually worldwide. The purpose of the studies presented in this paper is to develop a technology for the manufacture of a cell-derived equine rhinopneumonitis vaccine, as well as to assess the safety and immunogenicity of the newly developed vaccine in laboratory animals model. The object of the studies was the AK-2011 strain isolated from the horses suffering from rhinopneumonitis during an outbreak of abortions. The viability of the AK-2011 strain was assessed using a continuous line of calf trachea cells, a continuous line of calf kidney cells, a continuous line of sheep kidney cells, a continuous line of bovine kidney cells, a continuous line of green monkey kidney cells, a continuous line of Syrian hamster kidney cells, a primary trypsinized culture of horse kidney cells grown in tubes and flasks, and the AK-2011 laboratory strain of equine rhinopneumonitis virus with biological activity of 6.0 lg TCID_50/cm ³ . Sequencing and polymerase chain reaction (PCR) analysis were performed. The virus isolated from the ORF68 gene in Kazakhstan appeared to be the most similar to the T-953 and 2222-03 strains isolated in the USA and Australia, respectively, in terms of phylogenetics. As to primary infections, cytopathic effects (CPE) induced by the AK-2011 virus stain (dilution 10¹ ) in calf trachea and horse kidney cell cultures were stable from the 1^st to 10^th passages, with biological activity of 5.75-6.00 lg TCID_50/cm ³ . CPE caused by the virus were apparent on days 2-3, further developed intensively, and extended to 60-80% of the cell monolayer on days 5-7. The vaccine results can be used to immunize horses on farms against rhinopneumonia, and horses should be immunized twice with an interval of 2-3 months. This article is protected by copyright. All rights reserved.

First Detection and Genetic Characterization of New Equine Parvovirus Species Circulating among Horses in Korea

Equine parvovirus-cerebrospinal fluid (EqPV-CSF) and eqcopivirus (EqCoPV) are new parvovirus species (EqPVs) identified from various tissues (CSF, blood, and respiratory swabs) in horses with neurologic and respiratory diseases. In this study, we described the prevalence rate of EqPV-CSF and EqCoPV in 133 and 77 serum and fecal samples, respectively, using polymerase chain reaction. Further, we analyzed the potential risk factors for infection. We calculated the nucleotide and amino acid similarity and constructed phylogenetic trees. There was a moderate-to-high prevalence rate (EqPV-CSF: 3.8%; EqCoPV 9.8%) of each virus in serum; moreover, age, country of foaling, and clinical colic signs were significantly associated with the EqPVs infection. The newly identified EqPV-CSF/EqCoPV genomes had high nucleotide and amino acid identities with previously isolated strains in the USA. In phylogenetic analysis, they clustered and formed a new subgroup in the genus Copiparvovirus. To our knowledge, this is the first field epidemiologic study on EqPV-CSF and EqCoPV using both serum and fecal samples. Our findings demonstrate the risk factors for infection and could facilitate the development of disease prevention strategies.

Isothermal Nucleic Acid Amplification Technologies for the Detection of Equine Viral Pathogens

Simple Summary

Equine viral diseases remain a prominent concern for human and equine health globally. Many of these viruses are of primary biosecurity concern to countries that import equines where these viruses are not present. In addition, several equine viruses are zoonotic, which can have a significant impact on human health. Current diagnostic techniques are both time consuming and laboratory-based. The ability to accurately detect diseases will lead to better management, treatment strategies, and health outcomes. This review outlines the current modern isothermal techniques for diagnostics, such as loop-mediated isothermal amplification and insulated isothermal polymerase chain reaction, and their application as point-of-care diagnostics for the equine industry.

Abstract

The global equine industry provides significant economic contributions worldwide, producing approximately USD $300 billion annually. However, with the continuous national and international movement and importation of horses, there is an ongoing threat of a viral outbreak causing large epidemics and subsequent significant economic losses. Additionally, horses serve as a host for several zoonotic diseases that could cause significant human health problems. The ability to rapidly diagnose equine viral diseases early could lead to better management, treatment, and biosecurity strategies. Current serological and molecular methods cannot be field-deployable and are not suitable for resource-poor laboratories due to the requirement of expensive equipment and trained personnel. Recently, isothermal nucleic acid amplification technologies, such as loop-mediated isothermal amplification (LAMP) and insulated isothermal polymerase chain reaction (iiPCR), have been developed to be utilized in-field, and provide rapid results within an hour. We will review current isothermal diagnostic techniques available to diagnose equine viruses of biosecurity and zoonotic concern and provide insight into their potential for in-field deployment.