Equine herpesvirus 1 and 4
Equine herpesvirus 1 (EHV-1) infection in horses is responsible for upper respiratory infection in young horses and abortion, usually in late gestation, although recent work by Smith et al [1] and Allen et al [2] has demonstrated uterine or placenta damage without abortion during early gestation as well as myeloencephalopathy, generally in adult horses.
Equine herpesvirus 4 (EHV-4) had been thought to be a subtype of EHV-1, but through the use of molecular characterization techniques, it has been demonstrated to be a distinct viral species that can also cause abortions and respiratory disease. EHV-4 is responsible for upper respiratory infection in young horses and may rarely cause other problems, such as abortion [2–4]. Both viruses are capable of inducing myeloencephalopathy, although EHV-1 is clearly the more common cause of this form of the disease [4,5]. The respiratory disease is often silent or difficult to detect.
Despite this fact, the respiratory form of EHV-1 may be observed as an outbreak of fever and nasal discharge in a group of young horses. Disease may occur in individual horses or, sometimes, as case clusters. EHV-1 is highly contagious and is often responsible for significant economic losses as a result of abortion, neurologic disease, respiratory problems, loss of use, and even death. Outbreaks of this disease have been recognized for centuries among domestic horse populations.
An outbreak of any form of EHV-1 has a significant economic impact on the farm, veterinary hospital, or other venue where the outbreak occurs. The economic influence of an outbreak of EHV-1 or EHV-4 is a result of increased expense for medical treatment, lost time for training and performing, and death.
Authors: Stephen M. Reed, Ramiro E. Toribio
Source: https://www.vetequine.theclinics.com/
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