Equine viral arteritis (EVA) is a disease of horses caused by an RNA virus of the genus Arterivirus. The virus which causes EVA was first isolated from horses in Ohio in 1953 but the disease has afflicted equine animals worldwide for centuries. It has been more common in some breeds of horses in the United States, but there is no breed "immunity". In the UK, it is a notifiable disease. There is no known human hazard.
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Equine Arteritis Virus
The virus which causes EVA is the Equine Arteritis Virus (EAV). Arteriviruses are small, enveloped, animal viruses with an icosahedral core containing a positive-sense RNA genome. The family includes Equine arteritis virus (EAV), porcine reproductive and respiratory syndrome virus (PRRSV), lactate dehydrogenase elevating virus (LDV) of mice and simian haemorrhagic fever virus (SHFV).
Symptoms
Infected horses show variable symptoms including:
Some horses show no symptoms.
Transmission
There are a number of routes of transmission of the virus. The most frequent is the respiratory route. The virus can also be spread by the venereal route, including by artificial insemination. Stallions may become carriers.
Diagnosis
Because of the variability of symptoms, diagnosis is by laboratory testing. Blood samples, nasal swabs and semen can be used for isolation of the virus, detection of the viral RNA by polymerase chain reaction (PCR), and detection of antibodies by ELISA and virus neutralisation tests.
First UK Outbreak
The first outbreak of EVA in the UK was in 1993. The outbreak affected six premises and around 100 horses were infected. Further spread of the virus was prevented by movement restrictions.
Control
There is a vaccine available in the UK and Europe, however in laboratory tests it is not possible to distinguish between antibodies produced as a result of vaccination and those produced in response to infection with the virus. Management also plays an important part in the prevention of EVA.