Additional horses have tested positive for Equine Herpesvirus Myeloencephalopathy (EHM; Equine Herpesvirus – EHV) in Cooke County, Texas. The below was posted by the Texas Equine Veterinary Association and Equine Disease Communications Center.
The Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) recommends molecular diagnostic testing in lieu of serology testing if EHM / EHV is suspected. A positive serologic titer to equine rhinopneumonitis (ERP, EHV-1/4) indicates exposure either by vaccination or infection. The significance of this titer to the present condition is unknown. Serologic testing for the diagnosis of neurologic EHV-1 (EHM) is not reliable due to the inability to differentiate antibody response between different EHV-1 & 4 subtypes, the high prevalence of non-neurotropic EHV-1 in the horse population, and equine vaccination practices.
The EHV-1 polymerase chain reaction (PCR) test can differentiate between the neurotropic and non-neurotropic strains. Only horses in which neurotropic EHV-1 infection is suspected based on clinical signs and symptoms should be tested.