Latent equine herpesvirus-1 in trigeminal ganglia and equine idiopathic headshaking.

Abstract

BACKGROUND: Trigeminal neuralgia or neuropathic pain has been regarded as a putative cause of idiopathic headshaking in horses. Equine herpesvirus-1 (EHV-1) infection and resultant postherpetic pain have been suggested as a possible cause of such neuropathic pain. HYPOTHESIS/OBJECTIVES: To determine the presence of EHV-1 in the trigeminal ganglia of horses with idiopathic headshaking. ANIMALS: Nineteen horses: control (n = 11, 9 geldings, 2 mares, median age 11 years) and headshaking (n = 8, all geldings, median age 11.5 years) horses were sourced from the equine research herd and caseload at the Veterinary Medical Teaching Hospital. METHODS: Prospective study to determine the presence of EHV-1 latency in trigeminal ganglia of horses with idiopathic headshaking by real-time PCR detection of 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. Control horses were used for comparison. A house keeping gene (equine GAPDH) and positive and negative samples for EHV-1 were used for quality control. RESULTS: All samples from control horses and 7 of 8 headshaking horses were negative for EHV-1. One headshaking horse tested positive for a single copy of EHV-1 gene. CONCLUSIONS AND CLINICAL IMPORTANCE: This study does not support a role for EHV-1 infection and presumed postherpetic pain in the etiopathogenesis of equine headshaking.