Bluetongue: how to spot and report the disease

Advice on what to do if you suspect there is an outbreak of this infectious disease.

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Bluetongue is a notifiable insect-borne viral disease that affects sheep, cattle, other ruminants such as goats, and camelids such as llamas. It cannot be spread directly between animals and relies on the midge as a vector for transmission.

It does not affect people or food safety, but outbreaks can result in prolonged animal movement and trade restrictions.

Animal keepers should be very vigilant for any signs of notifiable disease and report any suspected cases to APHA immediately. When importing animals into Scotland, animal keepers should ensure they consider the risks carefully and check the health status of the animals. Animal keepers should also consult their vet on other measures, such as protective vaccination if appropriate.

Current situation

Following confirmation of bluetongue virus (BTV) in a non-imported animal in England in December 2023, Great Britain may no longer be considered a BTV-free country. The last outbreak occurred in the South of England in 2007. As a result of this, trade in live ruminant animals and germplasm from Great Britain to some countries (including Northern Ireland) is currently suspended. See: latest bluetongue situation in England.

Bluetongue has been reported in a number of European countries. See the current outbreak assessments and the map of restriction zones in place across Europe for more detail.

You should discuss the risks of importing stock from BTV affected countries with your vet.

Clinical signs

Infection with bluetongue can significantly compromise livestock welfare, both in terms of unpleasant symptoms and a potentially high mortality rate. The severity of disease varies among different species with symptoms being most severe in sheep, resulting in deaths, weight loss and disruption in wool growth. In highly susceptible sheep, morbidity can be as high as 100%. Mortality averages from 2 to 30%, but can be as high as 70%. Cattle often have a higher infection rate than sheep and demonstration and severity of clinical signs varies depending on the strain of virus.

Animals can recover from the disease. Such animals become immune to the strain with which they were infected and, after around 60 days, they stop shedding virus into the bloodstream, meaning that they no longer pose a risk in terms of onward infection of the midge population. However, there are long terms impacts on productivity and fertility.

If you keep livestock, you must continue to keep a close watch for, and report any suspicion of bluetongue disease in your animals.

In sheep

Sheep are more likely to show obvious clinical signs of bluetongue than cattle if they become infected. Signs of bluetongue in sheep include:

  • ulcers or sores in the mouth and nose
  • discharge from the eyes or nose and drooling from mouth
  • swelling of the lips, tongue, head and neck, and the coronary band (where the skin of the leg meets the horn of the foot)

Other clinical signs include:

  • red skin, as a result of blood collecting beneath the surface
  • fever
  • lameness
  • breathing problems
  • abortion
  • death

In cattle

Signs of the disease include:

  • lethargy
  • crusty erosions around the nostrils and muzzle
  • redness of the mouth, eyes, nose
  • reddening of the skin above the hoof
  • nasal discharge
  • reddening and erosions on the teats
  • fever
  • milk drop
  • not eating
  • abortion

Adult cattle may serve as a source of virus for several weeks while displaying little or no clinical signs of disease, and are often the preferred host for insect vectors.

In calves

Calves can become infected with bluetongue (BTV-8) before birth if the mother is infected while pregnant. Signs of infection include:

  • calves born small, weak, deformed or blind
  • death of calves within a few days of birth
  • abortions

Livestock keepers and vets should consider bluetongue as a possible cause for calves showing these signs.

Photos of clinical signs

We have published some photos of clinical signs of bluetongue disease on Flickr.

How bluetongue is spread

Bluetongue virus is mostly spread by certain species of biting midges (Culicoides species), many of which can be found throughout Great Britain.

Midges are infected with the virus when they bite an infected animal and the virus spreads when the infected midge bites an uninfected susceptible animal. Once a midge has picked up the bluetongue virus it will be a carrier for the rest of its life.

The time of year (midges are mainly active between April to November), meteorological conditions (temperature, wind speed and direction and rain), topography and the proximity and density of neighbouring farms with susceptible animals, are significant factors in any potential incursion and on how quickly, and how far midges can spread the disease.

Bluetongue virus can also be spread through biological products, such as blood, germinal products (semen or embryos), or the movement of infected animals.

Infected pregnant animals can, under certain circumstances, transmit the virus to their unborn offspring. Once born, the infected offspring could act as a source of bluetongue virus.

The severity of the infection depends upon the serotype of the virus and may also be affected by strain. New serotypes continue to be identified but only serotypes 1-24 are notifiable.

Practice good hygiene when vaccinating animals

Bluetongue can also be transmitted through dirty needles.

Animal keepers and vets should follow good practice when treating and vaccinating animals at risk of being infected with bluetongue.

Human health implications

The disease does not affect humans.

How to control the disease

You can help to prevent the disease by:

  • vaccinating your animals with a suitable authorised vaccine (there is no vaccine available for serotype 3)
  • responsibly source livestock
  • practising good biosecurity on your premises
  • remaining vigilant

If you import animals, speak to your vet before you decide to import them.

If bluetongue is confirmed and found to be circulating, APHA will place movement restrictions in zones around the infected premises. Further details on actions taken in the event of an outbreak of bluetongue are described in the contingency plan for exotic notifiable diseases and the GB bluetongue control strategy.

Biosecurity

Biosecurity is about being aware of the ways disease can spread and taking every practical measure to minimise the risk of disease spreading. The advice details practical things you can do on your farm to help prevent the introduction and spread of bluetongue to and from your animals.

Vaccination

Vaccination is the best way to protect animals from bluetongue virus serotypes 1, 2, 4 and 8. You should discuss with your vet whether vaccination would benefit your business. There is no vaccine available for serotype 3.

You need to comply with the requirements of a general licence if you wish to vaccinate animals located outside a restricted zone for bluetongue.

It can take up to six weeks for your animals to be fully immune, as your animals will require a period of time for immunity to develop following vaccination and may require two doses of the vaccine, three weeks apart.

Vets can apply to the Veterinary Medicines Directorate for a Special Import Certificate (SIC).

The certificate allows keepers to import safe and effective bluetongue vaccine directly from the EU to vaccinate their stock.

Licences

Apply for a specific licence to move animals in, out or within in a bluetongue disease control zone.

Importing animals from bluetongue affected countries

You should get advice from your vet about the risks and the health status of animals you want to import, before you import them.

If you import animals you should:

  • make sure animals comply with all of the requirements of the model health certificate to confirm they’ve come from a bluetongue free country or, where a vaccine exists, the animal has been correctly vaccinated against the right strains of bluetongue - this will depend on which country you’re importing from
  • fill in the bluetongue declaration GBHC172 if transiting through a bluetongue restricted territory
  • check if current issues relating to imports, exports and EU trade of animals and animal products affect your import
  • consider what additional guarantees the seller can provide - such as a pre-export test to prove the animal is not infected and has immunity to BTV
  • consider pre-vaccinating your flock or herd against the relevant strains of bluetongue before introducing new animals

Movement restrictions will apply to cattle or sheep imported from countries where bluetongue is known to be circulating. These restrictions will apply until the animals have been tested and confirmed free of the disease.

Animals that test positive for bluetongue may be culled or returned to the country of origin. Any animals which travelled in the same vehicle and are at risk of becoming infected may also be culled. No compensation will be paid for the culled animals. This only applies to imported animals. For UK born and bred animals that are culled to control the spread of disease, compensation will be paid at market value.

All other animals on the premises that are at risk of becoming infected will be placed under movement restrictions. These restrictions will apply until it’s confirmed that the disease has not spread. These restrictions may last several weeks.

Legislation

Powers for the control of bluetongue are laid out in:

Contact

If you suspect signs of any notifiable diseases, you must immediately notify your Scotland: field service local office at the Animal and Plant Health Agency (APHA). Failure to do so is an offence. 

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