Warble fly: how to spot and report the disease

How to spot warble fly, what to do if you suspect it and measures to prevent its spread.

Applies to England and Scotland

Warble fly mainly affects cattle. It can also affect:

  • horses
  • deer

Warble fly doesn’t affect humans.

The last outbreak in Great Britain was in 1990.

If you suspect the disease in Scotland, you must tell the Animal and Plant Health Agency (APHA) immediately. Failure to do so is an offence.

Warble fly is a notifiable disease in cattle only in Scotland as the England and Wales regulations were revoked from 1 April 2015.

How to spot warble fly

The main sign of warble fly is large, soft and painful swellings on the back of the animal of up to 3 millimetres wide.

How warble fly is spread

The disease is spread by the warble fly, which lays eggs on the hide of animals.

Preventing and controlling warble fly

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

If you report suspicion of warble fly in Scotland, APHA vets will investigate.

If warble fly is confirmed the outbreak will be controlled in line with the Scotland exotic diseases of animals contingency framework plan.

An approved list of products to treat warble fly can be found on the Veterinary Medicines Directorate Product Information Database by using the predefined search ‘Warble’.

Further information on prevention and control

Controls to prevent disease

What happens when a notifiable disease is suspected or confirmed

Legislation on warble fly

The main legislation on warble fly is the Warble Fly (Scotland) Order 1982.

Published 26 August 2014
Last updated 10 July 2018 + show all updates
  1. Added link to Veterinary Medicines Directorate Product Information Database

  2. Updated as warble fly is only a notifiable disease in Scotland since 1 April 2015.

  3. AHVLA documents have been re-assigned to the new Animal and Plant Health Agency (APHA).

  4. First published.