There are over 27 different types (serotypes) of bluetongue virus (BTV) which can infect domestic animals such as sheep, goats, and cattle, along with wild animals like buffaloes, deer, antelope and camels. BTV belongs to the family Reoviridae, genus Orbivirus with 20 recognised species in the genus. It is a complex non-enveloped virus with a capsid and double stranded RNA genome consisting of 10 segments of different sizes.
- Bluetongue is a notifiable disease and should be reported.
Please see the Defra website for advice on how to spot and report the disease.
BTV causes bluetongue in its mammalian hosts, with each serotype producing similar symptoms.
- Reddening of the mucosal membranes
- Sores on the nose, gum and dental pads
- Swelling of the face, lips and tongue (“bluetongue”). Animals may also develop breathing difficulties if the tongue swells
- BT can lead to death and can cause abortion or deformities in lambs or calves.
BTV is spread mainly by biting midges (Culicoides), but other biting insects may also transfer the virus. BTV can be transferred from a ruminant mother to her foetus during pregnancy and by infected meat consumed by dogs. It could also be spread by contaminated objects (fomites) such as needles or surgical equipment.
BTV is present in many parts of the world including Southern Europe, the Middle East and North Africa therefore there are lots of different types close to our borders which pose a threat to our livestock industry.
Impact for Society – what are we doing?
There is no treatment available other than supportive therapy. The Pirbright Institute is the European reference laboratory for diagnosing BT outbreaks which occur in the EU and performs laboratory tests to establish the serotype causing the outbreak. Due to work carried out at the Institute, the UK was able to vaccinate large numbers of livestock in 2008 against serotype 8, which prevented huge economic losses and the death of lots of animals.
The difficulty in combatting BT is that infection or vaccination of an animal with one serotype does not confer immunity to any of the other serotypes. It is virus protein 2 (VP2), located at the surface of the virus, that both determines the serotype and activates immune responses. Vaccines exist for just a few of the serotypes, so knowing the serotype of BTV that is causing a given outbreak is important in finding if an appropriate BT vaccine is available.
Improving diagnostics is a key area of research the Institute participates in. The gene that encodes VP2 of 24 serotypes has now been sequenced, and a test has been developed to identify them (using PCR). These tests are much more rapid than conventional virus neutralisation tests, giving results within a day rather than three weeks or so. The Institute is also working on novel vaccines which may provide protection against multiple BTV types.