Antemortem detection of latent infection with neuropathogenic strains of equine herpesvirus-1 in horses.

The research article presents a new method for diagnosing horses with latent neuropathogenic strains of equine herpesvirus-1 (EHV-1), using a magnetic bead, sequence-capture, nested PCR assay technique on the mandibular lymph node (MLN) tissues. The study reveals that the technique possess high detection rates in comparison to other methods, and could become a potential tool for screening horses for latent neuropathogenic EHV-1 infection.

Research Objectives

• The primary goal of the study is to assess a method for identifying horses latently infected with neuropathic strains of EHV-1.
• The researchers devised an experimental set-up where 36 adult mares were examined, out of which 24 were purposefully infected with either neuropathogenic or non-neuropathogenic EHV-1 when they were weanlings.

Methods

• Mandibular lymph node (MLN) tissue was collected from each horse via biopsy during general anesthesia. The DNA was then isolated from these samples.
• The purified MLN DNA samples underwent testing for EHV-1 DNA using a magnetic bead, sequence-capture, nested PCR assay.
• If EHV-1 DNA was found, the researchers sequenced the 256-bp DNA fragments amplified via sequence-capture nested PCR to identify the nucleotide at the polymorphic site determining the pathotype.

Results

• The researchers discovered latent viral DNA in 26 out of the 36 mares examined, denoting a detection rate of 72%.
• Both neuropathogenic and nonneuropathogenic EHV-1 genotypes were identified in the latently infected horses.
• In cases where horses had been previous infected with known EHV-1 pathotypes, the open reading frame 30 genotype of latent EHV-1 correlated to the strain inoculated 4-5 years earlier.
• Latent viral DNA was identified in 10 of the 12 mares that were inoculated as weanlings with neuropathogenic strains of EHV-1.
• Using sequence-capture PCR, the detection rate of EHV-1 latency was noted to be twice the rate achieved by other conventional nested or real-time PCR assays on the same MLN DNA samples.

Conclusion

• The magnetic bead, sequence-capture, nested PCR technique established in this research showed an improved capacity to identify DNA from latent neuropathogenic strains of EHV-1 in live horse MLN specimens.
• The technique appears promising for its application to screen horses for latent neuropathogenic EHV-1 infection in the future.