This is a viral disease spread by midge bites.

Bluetongue is caused by a virus and is spread by midges.

Why is bluetongue important?

The disease may be mild in deer and they may not show any outward signs. However, deer can act as a reservoir for the disease, which may then spread to domestic livestock.

Signs of bluetongue

Bluetongue restricts the blood supply to the tongue and lips, turning them blue or even black and giving the disease its name.

Other signs of the disease include:

  • swelling of the mouth, head and neck
  • discharge from the eyes and nose
  • drooling – caused by ulcers in the mouth

Susceptibility to bluetongue

The susceptibility of deer to the disease depends on:

  • species of deer
  • strain of bluetongue virus (BTV)


Epizootic haemorrhagic disease is similar to bluetongue and is caused by a virus related to BTV.

More about bluetongue

Visit the Scottish Government's web page on bluetongue to learn more about the clinical signs. There is also information on the current disease situation in Scotland and guidance on biosecurity (measures to prevent the disease).

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