Antemortem detection of latent infection with neuropathogenic strains of equine herpesvirus-1 in horses.
OBJECTIVE
To evaluate a technique for identifying horses latently infected with neuropathogenic strains of equine herpesvirus-1 (EHV-1).


METHODS
36 adult mares, 24 of which were experimentally infected as weanlings with neuropathogenic or nonneuropathogenic EHV-1.


METHODS
Mandibular lymph node (MLN) tissue was obtained from each horse via biopsy during general anesthesia. Purified DNA from MLNs was tested for EHV-1 DNA by use of a magnetic bead, sequencecapture, nested PCR assay. For MLNs that contained EHV-1 DNA, the 256-bp DNA fragments amplified via sequence-capture nested PCR were sequenced to determine the nucleotide at the polymorphic site that determines pathotype (ie, neuropathotype [G(2254)] or non-neuropathotype [A(2254)]).


RESULTS
Latent viral DNA was detected in 26 of the 36 (72%) mares tested. Neuropathogenic and nonneuropathogenic EHV-1 genotypes were detected in the latently infected horses. In each mare previously infected with known EHV-1 pathotypes, the open reading frame 30 genotype of latent EHV-1 was identical to that of the strain that had been inoculated 4 to 5 years earlier. Latent viral DNA was detected in 10 of the 12 mares that were inoculated as weanlings with neuropathogenic strains of EHV-1. The detection rate of the sequence-capture PCR method for EHV-1 latency was double that of conventional nested or realtime PCR assays performed on the same MLN DNA preparations.


CONCLUSIONS
The magnetic bead, sequence-capture, nested PCR technique enabled low-threshold detection of DNA from latent neuropathogenic strains of EHV-1 in MLN specimens from live horses. The technique may be used to screen horses for latent neuropathogenic EHV-1 infection.
Allen
George P
GP
Department of Veterinary Science, Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, 40546-0099, USA.
D000818:Animals; D004279:DNA, Viral / Q000032:analysis; D005260:Female; D006566:Herpesviridae Infections / Q000662:veterinary*; D004861:Herpesvirus 1, Equid / Q000145:classification* / Q000302:isolation & purification*; D006734:Horse Diseases / Q000821:virology*; D006736:Horses; D008198:Lymph Nodes / Q000821:virology; D017735:Virus Latency / Q000502:physiology*
D004279:DNA, Viral