Equine viral arteritis.

The research paper focuses on equine viral arteritis (EVA), a virus that causes respiratory disease and abortion in horses. The study explores EVA’s history, symptoms, and worldwide prevalence, its clinical effect on horses, its transmission modes, its occurrence in other equidae, and the strategies used to prevent the virus’ introduction into populations.

Background and Global Prevalence of EVA

• EVA was recognized as a distinct viral infection in horses after a 1953 outbreak in Ohio. It was often confused with other similar diseases caused by equine herpesvirus 1 and 4, and equine influenza virus.
• The seroprevalence (the level of a pathogen in a population as measured in blood serum) of EVA varies significantly between countries and between different breeds in the same country. It is generally lower in Thoroughbreds and higher in Standardbreds.
• Despite an increase in reported incidents of EVA since an outbreak in Kentucky Thoroughbreds in 1984, it’s believed that many cases remain undiagnosed.

Clinical Effects and Transmission Modes of EVA

• EVA infection outcomes are highly variable. Symptoms usually range from overt disease with fever, loss of appetite, nasal and ocular discharge, conjunctivitis, and edema to a milder, often subclinical infection.
• The most severe form of EVA infection can lead to high abortion rates in pregnant mares and, infrequently, death in foals.
• The virus can be transmitted through the semen of stallions, which complicates disease containment as many infected stallions might shed the virus for life. Virus transmission can occur via natural coverage, artificial insemination, or respiratory route among susceptible in-contact horses.

EVA in Other Equidae

• While the virus was reported to be prevalent in donkeys in Morocco, the recent investigative research has only focused on horses.
• Recent studies in South Africa confirmed that donkeys can be naturally infected by and harbor EVA. They also showed that asinine arteritis virus and horse arteritis strains are very closely related, suggesting cross-species infection could occur.
• Despite widespread EVA infection rates among donkeys in some areas, no clinical disease has been reported in South Africa.

Preventive Measures Against EVA

• Preventive measures in South Africa, such as mandatory testing and post-importation quarantine of imported horses, and testing of local stallions before the breeding season, have been effective in preventing EVA spread to horses.
• The research called for further data collection, specifically, sera from areas where horses and donkeys are in contact, to ascertain local strains of EVA transfer between these two species.