Prevalence of equine herpesvirus type 1 in trigeminal ganglia and submandibular lymph nodes of equids examined postmortem.

The objective of this study was to detect and characterise the biovar of equine herpesvirus type 1 (EHV-1) from submandibular lymph nodes (SMLNs) and trigeminal ganglia from 153 equids undergoing routine postmortem examination for various medical and surgical reasons. A combination of nucleic acid precipitation and preamplification steps was used to increase the analytical sensitivity of the analysis. The presence of latent EHV-1 was determined when tissue samples were PCR-positive for the glycoprotein B (gB) gene and the DNA polymerase (ORF 30) gene of EHV-1 in the absence of detectable late structural protein gene (gB gene) mRNA. The SMLNs of five of the study animals (3.3 per cent) were PCR-positive for the gB gene of EHV-1. Two SMLNs carried a latent neurotropic strain of the virus, whereas three SMLNs were PCR-positive for both neurotropic and non-neurotropic EHV-1. A total of 30 trigeminal ganglia collected from 19 horses were PCR-positive for the gB gene of EHV-1. Nine trigeminal ganglia harboured either latent non-neurotropic or neurotropic EHV-1 strains. Twelve trigeminal ganglia contained both latent neurotropic and non-neurotropic EHV-1. The prevalence and distribution of EHV-1 biovars among the study horses appeared to be influenced by their breed and the type of tissue tested.