Equine Herpesvirus-1 Myeloencephalopathy

One of the most prevalent and costly infectious viral diseases of horses is EHV-1. This virus can result in devastating consequences for horses when large scale outbreaks of either respiratory, abortion or myeloencephalopathy occur. The respiratory form of this disease destroys epithelium of the upper airway, while abortions caused by this virus result in infection and death of the fetus and finally the neurological form of the disease results from infection of the endothelial cells lining the nervous system leading to vasculitis and necrosis. EHV – 1 isolates recovered from several outbreaks contain a mutation of EHV-1 (A2254 → G mutation in genomic open reading frame # 30) virus that possesses enhanced neuropathogenecity. EHV-1, including the mutated strain appear to be entrenched in many horse populations. Work by Allen et al has shown that this Herpesvirus mutant has established a well-entrenched reservoir of latently infected horses. Molecular characterization from archived isolates of EHV – 1 from Kentucky abortions demonstrates a statistically significant increase in the proportion of isolates that contain the ORF30 A2254 → G mutation over the last 50 years.
This virus has the potential to increase its virulence and expand its cellular tropism. Outbreaks of EHM have been observed since 1966 but recently there appears to be an increase in the morbidity and mortality associated with the disease. Horses demonstrating neurological signs associated with outbreaks of EHV-1 were more sporadic prior to 2000. […]