Equine herpesvirus neurological disease.

The article discusses research on the prevalence of a gene mutation in Equine herpesvirus-1 (EHV-1) in the normal population of horses in Kentucky. The study looks at the implications of this for the prevalence and incidence of EHV abortion and neurological disease.

Molecular Pathogenesis of EHV-1

• The paper refers to EHV-1 neurological disease as an emerging infectious disease. Abortion due to EHV-1 has been decreasing in horse breeding countries, but instances of EHV-1 neurological disease are increasingly reported.
• Recent studies have linked a specific mutation in the EHV-1 polymerase gene with increased chances of viruses coming from cases of neurological disease. This discovery has influenced the development of tests to detect the mutation.
• However, the presence of the mutation was not definitive for all cases of EHV-1 neurological disease. About 15% of the samples from cases of the disease did not contain the mutation in the polymerase gene.

Impact of the Gene Mutation

• The research suggests that foals infected with the neuropathogenic strain of EHV-1 exhibited amplified and extended leucocyte associated viraemia when compared to foals infected with non-neuropathogenic or abortigenic strains of the virus.
• The significance of this mutation on the pathogenesis of EHV-1 is a current subject of many studies in virology labs around the world.

The Prevalence of EHV-1

• EHV-1 is a crucial viral pathogen of horses and was first recognized as a cause of abortion in Kentucky in 1932. The disease’s clinical manifestation and the epidemiology of the infection are well known globally.
• EHV-1 is maintained in the population as a sub-clinical infection among foals and young horses and spread further among older animals during periods of recrudescence and disease.

Outbreaks of EHV-1 Disease

• Until recently, outbreaks of EHV-1 disease were usually seen as infections in pregnant mares causing abortions. Nevertheless, the occurrence of outbreaks involving neurological disease has significantly increased in the past decade.

Local and Systemic Infection/Disease of EHV-1

• The herpesvirus first replicates in the respiratory organs, causing respiratory disease. The clinical signs of this disease are indistinguishable from those caused by the closely related EHV-4 virus.
• The virus can progress from a local to a systemic infection which results in more severe conditions such as abortion and neurological disease.