Characterization of viral loads, strain and state of equine herpesvirus-1 using real-time PCR in horses following natural exposure at a racetrack in California.
Abstract: The objective of this study was to determine viral loads, strain (neuropathogenic versus non-neuropathogenic) and state (lytic, non-replicating, latent) of equine herpesvirus-1 (EHV-1) by real-time polymerase chain reaction (PCR) in the blood and nasopharyngeal secretions of adult horses following natural exposure. The index case, a 4-year-old Thoroughbred gelding with confirmed EHV-1 myeloencephalopathy, as well as potentially exposed horses, were sampled over a period of 3 weeks. The study population comprised of 39 adult Thoroughbred horses and 35 adult "pony" and outrider horses of various breeds housed at a racetrack in Northern California. Blood samples and nasopharyngeal secretions (NPS) from all horses were tested on several occasions for EHV-1 DNA viral loads, targeting the glycoprotein B (gB) gene, viral strain, targeting the ORF 30 gene, and transcriptional activity of EHV-1, targeting the gB gene and latency-associated transcripts (LATs). Viral loads and transcriptional activity of the gB gene declined rapidly in the index case following antiviral treatment. The prevalence of EHV-1 infection in NPS determined by PCR slowly decreased over the 22 day study period from 25% to 14%. The initial surveillance showed multiple clusters of exposure, one associated with the index case and two related to horses that had recently returned from a different racetrack. Viral strain differentiation showed that only two horses (the index case and a neighboring horse) were infected with only a neuropathogenic strain, while all other horses were infected with either a non-neuropathogenic strain or were dually infected with both neuropathogenic and non-neuropathogenic strains. In most cases, the virus was present in either a lytic or a non-replicating form, while latent virus was found in blood and NPS much less frequently. The molecular approach used in this study showed promise for assessing the risk of exposing other horses to EHV-1 and for studying viral kinetics in infected horses.
Publication Date: 2007-11-19 PubMed ID: 18024200DOI: 10.1016/j.tvjl.2007.09.018Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The study aimed to assess the levels, types, and activity states of equine herpesvirus-1 (EHV-1) in horses in a California racetrack using real-time PCR tests. The researchers found different strains of the virus and observed its activity decrease after treatment.
Objective and Methodology
- The research aimed to investigate the viral loads (quantity), strain (neuropathogenic versus non-neuropathogenic), and state (lytic, non-replicating, latent) of equine herpesvirus-1 (EHV-1) in horses naturally exposed to the virus.
- Real-time polymerase chain reaction (PCR) was used to measure these parameters in the blood and nasopharyngeal secretions of adult horses.
- The study sample comprised 39 adult Thoroughbred horses and 35 adult “pony” and outrider horses of various breeds, housed at a racetrack in Northern California.
- Both blood samples and nasopharyngeal secretions (NPS) from all horses were tested repeatedly for EHV-1 DNA viral loads, viral strain, and transcriptional activity of EHV-1.
Findings: Viral Loads and Strains
- The researchers observed that the viral loads and transcriptional activity of the glycoprotein B (gB) gene dramatically decreased in the index case after antiviral treatment.
- The incidence of EHV-1 infection in NPS, as established by PCR, gradually lessened over the 22-day study period, dropping from 25% to 14%.
- At the beginning of the study, multiple exposure clusters were identified. One was related to the index case, and two were linked to horses that had recently returned from another racetrack.
- Upon differentiating the viral strains, it was found that only two horses (the index and a neighboring horse) were infected solely with a neuropathogenic strain. The rest were either infected with a non-neuropathogenic strain or had contracted both neuropathogenic and non-neuropathogenic strains.
Findings: Status of the Virus
- The researchers discovered that, in most cases, the virus was present in a lytic or non-replicating state.
- Latent viruses were found much less frequently and were detected in blood and NPS samples.
Significance and Potential Applications of the Study
- The molecular technique used in this study provides a potential tool for evaluating the risk of EHV-1 transmission among horses and for studying viral kinetics in horses already infected.
Cite This Article
APA
Pusterla N, Wilson WD, Mapes S, Finno C, Isbell D, Arthur RM, Ferraro GL.
(2007).
Characterization of viral loads, strain and state of equine herpesvirus-1 using real-time PCR in horses following natural exposure at a racetrack in California.
Vet J, 179(2), 230-239.
https://doi.org/10.1016/j.tvjl.2007.09.018 Publication
Researcher Affiliations
- Department of Medicine and Epidemiology, University of California, Davis, CA 95616, USA.
MeSH Terms
- Animals
- California
- DNA, Viral / chemistry
- DNA, Viral / genetics
- Disease Outbreaks / veterinary
- Disease Reservoirs / veterinary
- Disease Reservoirs / virology
- Female
- Herpesviridae Infections / epidemiology
- Herpesviridae Infections / transmission
- Herpesviridae Infections / veterinary
- Herpesviridae Infections / virology
- Herpesvirus 1, Equid / isolation & purification
- Horse Diseases / epidemiology
- Horse Diseases / transmission
- Horse Diseases / virology
- Horses
- Male
- Polymerase Chain Reaction / methods
- Polymerase Chain Reaction / veterinary
- Prevalence
- Viral Load / veterinary
- Virus Latency
Citations
This article has been cited 16 times.- Tsai MS, François S, Newman C, Macdonald DW, Buesching CD. Infection with a Recently Discovered Gammaherpesvirus Variant in European Badgers, Meles meles, is Associated with Higher Relative Viral Loads in Blood.. Pathogens 2022 Oct 6;11(10).
- Pusterla N, Barnum S, Young A, Mendonsa E, Lee S, Hankin S, Brittner S, Finno CJ. Molecular Monitoring of EHV-1 in Silently Infected Performance Horses through Nasal and Environmental Sample Testing.. Pathogens 2022 Jun 24;11(7).
- Price D, Barnum S, Mize J, Pusterla N. Investigation of the Use of Non-Invasive Samples for the Molecular Detection of EHV-1 in Horses with and without Clinical Infection.. Pathogens 2022 May 13;11(5).
- Thieulent CJ, Sutton G, Toquet MP, Fremaux S, Hue E, Fortier C, Pléau A, Deslis A, Abrioux S, Guitton E, Pronost S, Paillot R. Oral Administration of Valganciclovir Reduces Clinical Signs, Virus Shedding and Cell-Associated Viremia in Ponies Experimentally Infected with the Equid Herpesvirus-1 C(2254) Variant.. Pathogens 2022 May 4;11(5).
- Pusterla N, Barnum S, Miller J, Varnell S, Dallap-Schaer B, Aceto H, Simeone A. Investigation of an EHV-1 Outbreak in the United States Caused by a New H(752) Genotype.. Pathogens 2021 Jun 13;10(6).
- Samoilowa S, Giessler KS, Torres CEM, Hussey GS, Allum A, Fux R, Jerke C, Kiupel M, Matiasek K, Sledge DG, Goehring LS. Equid herpesvirus-1 Distribution in Equine Lymphoid and Neural Tissues 70 Days Post Infection.. Pathogens 2021 Jun 5;10(6).
- Giessler KS, Samoilowa S, Soboll Hussey G, Kiupel M, Matiasek K, Sledge DG, Liesche F, Schlegel J, Fux R, Goehring LS. Viral Load and Cell Tropism During Early Latent Equid Herpesvirus 1 Infection Differ Over Time in Lymphoid and Neural Tissue Samples From Experimentally Infected Horses.. Front Vet Sci 2020;7:621.
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