Detailed guide: Equine viral encephalomyelitis: how to spot and report the disease

Equine viral encephalomyelitis is a disease which can be caused by several viruses (known as equine encephalitis viruses). They include, but are not limited to:

• Japanese encephalitis
• Western equine encephalomyelitis virus
• Eastern equine encephalomyelitis virus
• Venezuelan equine encephalomyelitis virus
• West Nile virus

Encephalomyelitis means inflammation of the brain and spinal cord.

Equine viral encephalomyelitis can be fatal, although some animals will recover from the disease.

Animals affected by the disease

Equine viral encephalomyelitis mainly affects members of the equid family, such as:

• horses
• donkeys
• mules
• zebras

Other animals can also be affected, such as:

• cattle, sheep and goats
• pigs
• birds, including poultry
• dogs
• rodents

Humans can also be affected.

How to spot equine viral encephalomyelitis in equid species

Clinical signs can be different depending on which virus the animal has. Some animals will not show any signs at all.

You may spot these signs soon after infection:

• fever for several days
• lack of appetite
• loss of weight and condition
• depression
• stiffness and weakness

You may spot these signs in the later stages of infection:

• behavioural changes – such as circling, head pressing or aimless wandering
• hyperexcitability
• blindness
• lack of coordination and balance
• inability to move
• staggering or standing with an open stance
• seizures

Infections that have similar signs

You may also see similar clinical signs if your animal is infected with one of the following:

• rabies
• tetanus
• African horse sickness
• bacterial meningitis
• toxic poisoning
• leucoencephalomalacia (Fusarium intoxication)

You must report these signs even if you think your animal does not have equine viral encephalomyelitis.

How equine viral encephalomyelitis spreads

The viruses that cause equine viral encephalomyelitis are mainly spread by mosquitoes. Other animals, including wild birds or rodents, can also carry the virus between different areas.

Only some types of mosquito can spread the virus. This means that if an infected horse did enter the UK, the possibility of the disease spreading would be low.

There has never been an outbreak of equine viral encephalomyelitis in the UK.

Risk to humans

Humans can be infected by equine encephalitis viruses if they are bitten by an infected mosquito. Most people have no symptoms.

An infected person or horse cannot pass the virus directly to others.
In rare cases, the virus can be spread during surgical interventions, such as a blood transfusion.

If your animal displays signs of infection and you are worried about your health, contact your GP for advice.

Prevent and control equine viral encephalomyelitis

If you import animals, you must follow the rules to make sure they are free from disease and fit to travel.

You can help prevent the disease by:

• being familiar with the clinical signs of equine viral encephalomyelitis
• practising strict biosecurity on your premises

If the disease is confirmed, the outbreak will be controlled in line with the contingency plan for exotic notifiable diseases.

Find out what happens when a notifiable disease is suspected or confirmed.

Legislation

The main legislation covering the control of equine viral encephalomyelitis, is the Infectious Diseases of Horses Order 1987.