What we offer for equine herpesvirus-1 (EHV-1) detection by qPCR:

  • Quantitation of EHV-1 at the genomic DNA level. The viral load is expressed as the absolute number of EHV-1 (glycoprotein B gene) per million blood/nasopharyngeal cells. In nasal secretions, the viral load allows veterinarians to indirectly assess the infectious nature of an animal shedding EHV-1, while results in blood help determine the level of viremia and the risk for a horse to eventually develop neurologic signs or abortion.
  • Genotype differentiation. Detection of a single mutation on the ORF 30 gene of EHV-1 at nucleotide position 2254 allows differentiation of neuropathogenic (G2254) and non-neuropathogenic (A2254) genotypes. The results will be reported as presence of neuropathogenic or non-neuropathogenic EHV-1 strains. Please keep in mind that up to 24% of horses with neurologic disease can be infected with the "non-neuropathogenic" form, suggesting that other factors may also contribute to the onset of equine herpesvirus myeloencephalopathy (EHM). Differentiation will be performed on all samples submitted for EHV-1 testing at no additional cost.
  • Detection of EHV-1 transcripts at the cDNA level. This approach helps characterize the viral state and determines if the virus is lytic or non-replicating. The results will be qualitatively reported as positive (evidence of active replication = lytic virus) or negative (absence of active replication). This option is only available when a sample is positive for EHV-1 at the genomic DNA level, and must be requested by the submitting veterinarian. Additional charges apply.

Please refer to our test list for pricing and sample information. EHV-1 qPCR is offered as a standalone test, and also as part of the Equine Respiratory Panel.

How results are reported:
PCR results for EHV-1 are expressed qualitatively (positive or negative) and quantitatively in the case of a positive result. The viral load of a sample is calculated by the absolute number of EHV-1 (glycoprotein B gene) per million cells (either blood cells or nasopharyngeal cells). Diseased horses (neurological or febrile) commonly have high (greater than 1x10^4) viral loads in blood and nasal secretions. Subclinical horses commonly have low (less than 1x10^3) to moderate (1x10^3 – 1x10^4) viral loads only in nasal secretions. The absolute number should be used judiciously and allow comparisons between samples taken at different time points. Viral load ranges are only suggestions and are not currently well-defined. Neuropathogenic and non-neuropathogenic genotypes are expressed qualitatively as positive or negative.


N. Pusterla, S. Mapes, W. D. Wilson Use of viral loads in blood and nasopharyngeal secretions for the diagnosis of EHV-1 infection in field cases Veterinary Record (2008)162; 728-729 PDF

D.P. Lunn, N. Davis-Poynter, M.J.B.F. Flaminio, D.W. Horohov, K. Osterrieder, N. Pusterla, and H.G.G. Townsend EHV1 consensus statement J Vet Intern Med(2009);23:450–461 PDF

N. Pusterla, W. David Wilson, John E. Madigan, Gregory L. Ferraro Equine herpesvirus-1 myeloencephalopathy: A review of recent developments The Veterinary Journal (2009) 180;279–289 PDF

N. Pusterla, S.B. Hussey, S. Mapes, C. Johnson, J.R. Collier, J. Hill, D.P. Lunn, W.D. Wilson Molecular investigation of the viral kinetics of equine herpesvirus-1 in blood and nasal secretions of horses after corticosteroid-induced recrudescence of latent infection J Vet Intern Med (2010) 24;1153-1157 (link to article)

EHV-1 Control Measures:

EHV-1 information regarding handling of sick horses, diagnostic testing, control measures, and vaccinations from the Center of Equine Health, UC Davis