West Nile fever: how to spot and report the disease

How to spot West Nile fever, what to do if you suspect it and measures to prevent its spread.

West Nile fever affects a variety of animals including but not limited to:

  • horses
  • birds
  • humans

West Nile fever is a notifiable disease. That means if you suspect it you must tell the Animal and Plant Health Agency (APHA) immediately. Failure to do so is an offence.

How to spot West Nile fever

In horses clinical signs can include:

  • lack of energy
  • loss of coordination
  • weakness in limbs leading to stumbling

Some horses will not show any signs at all.

Birds are the main carrier of West Nile fever, but not all species show signs of the disease.

Risk to humans from West Nile fever

Humans can be affected by West Nile fever. The most common symptoms are fever and headache.

Other symptoms can include:

  • rash
  • conjunctivitis (red eyes)
  • swollen lymph nodes, for example in the neck

If your symptoms are mild, they will usually get better without treatment after a few days or weeks.

In severe cases, fever and headache are intense and other symptoms develop quickly including:

  • stiff neck
  • disorientation
  • muscle weakness

Severe cases can end in paralysis, coma or death.

You can read more about West Nile fever in humans at NHS Choices.

How West Nile fever is spread

The disease is spread by mosquitoes. It is not spread directly between animals.

Birds are the most common carriers and may spread West Nile fever between countries when they migrate.

Preventing and controlling West Nile fever

You can help prevent the disease by practising strict biosecurity on your premises.

If you report suspicion of West Nile fever, APHA vets will investigate.

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

Further information on prevention and control

Controls to prevent disease

What happens when a notifiable disease is suspected or confirmed

Legislation on West Nile fever

The main legislation relating to control of West Nile fever is the Infectious Diseases of Horses Order 1987.