What is bluetongue?
Bluetongue is a notifiable midge-borne viral disease which can infect all ruminants, such as cattle, goat, deer, camelids (e.g. llama's and alpacas) and sheep where clinical signs are more apparent than in other ruminants. Bluetongue is different from many other diseases in that disease is confirmed as being present in a country only when there is evidence of it circulating in the midge population rather than when a single infected animal is identified.
What are the symptoms?
The clinical signs in sheep can include:
- fever
- swelling of the head and neck
- inflammation and ulceration of the mucous membrane of the mouth, nose and eyelids
- lameness
- loss of muscle tone and weakness
- haemorrhages in the skin and other tissues
- respiratory signs such as froth in the lungs and an inability to swallow and discolouration; swelling of the tongue.
Although bluetongue usually causes no apparent illness in cattle or goats, cattle may display clinical signs including:
- nasal discharge
- swelling and ulceration of the mouth
- swollen teats.
What are the implications for infected animals?
Infection with bluetongue can significantly compromise livestock welfare, both in terms of unpleasant symptoms (see above) and a potentially high mortality rate (around 30%). 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.
How is bluetongue spread?
Bluetongue can generally only be transmitted by the bite of certain species of midge - it does not spread directly from animal to animal. However, there is evidence that the BTV-8 can be transmitted from mother to young during pregnancy. The disease can be spread geographically both by vector movements and the movements of infected animals that local midges at the destination then bite.
How do we think the first animal in the UK caught the disease?
Defra's first epidemiology report into the UK bluetongue outbreak, based on the situation up to 19 October 2007, concluded that the infection was likely to have been initially introduced into Norfolk, Suffolk and Essex on the night of 4th/5th August 2007 by windborne transmission of infected midges from continental Europe.
Is bluetongue a concern for public health reasons?
No, bluetongue is a disease of ruminant animals, and it does not affect humans. There are no public health implications.
Is meat safe to eat?
There are no food safety implications from either infected or vaccinated animals. The bluetongue virus requires live hosts, either livestock or midge, to survive.
Will the countryside be closed in the event of an outbreak?
No. The countryside will remain open.
Can susceptible animals be vaccinated against bluetongue?
No. From the 5th July 2011 the general licence to vaccinate against serotype BTV8 was revoked therefore prohibiting vaccination.
Where is BTV8 now and what other strains of bluetongue are present in continental Europe?
Map showing bluetongue situation in Europe
What can be done to reduce the threat to Scotland?
The most important defence for Scotland is for the livestock industry to avoid sourcing livestock from high-risk areas and to ensure that they know the health and vaccination status of any animals brought into Scotland.