What we offer for EHV-1 detection:
• Quantitation of genomic DNA level (see recent study on the viral loads of EHV-1 in clinically and subclinically infected horses). The viral load would allow veterinarians to indirectly assess the infectious nature of an animal shedding EHV-1. The results in blood would also help to determine the level of viremia and determine the risk for a horse to eventually develop neurologic signs or abortion.
• Detection of the different genotypes to differentiate between the neuropathogenic and non-neuropathogenic strains. The results will be reported as presence of neuropathogenic, non-neuropathogenic or dual EHV-1 strains. Please keep in mind that up to 24% of horses with neurologic disease can be infected with "non-neuropathogenic" form, suggesting that other factors may also contribute to the onset of equine herpesvirus myeloencephalopathy.
• Detection of EHV-1 transcripts at the cDNA level. This approach will help to characterize the viral state and determine 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 is only available when a samples is positive for EHV-1 at the genomic DNA level.
How results will be 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.
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
Nicola 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
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