What is bluetongue disease?

I’ve been kind of aware that there is another dreadful livestock disease called blue tongue or all-in-one-word bluetongue, mainly from reading the foot and mouth discussions and news. But it wasn’t until a confirmed case of bluetongue disease in the UK on the 22nd September that I sought to find out exactly what it is, how it spreads and the nature of the threat. It turns out that the spread of bluetongue to the UK has been pretty much expected, but the actual arrival of two positively diagnosed cases is another terrible blow to farmers already reeling from restrictions imposed for the ongoing foot-and-moth outbreak and the summer floods which destroyed vast areas of arable crops.

The first place to research is warmwell, the quaintly designed but timely and authoritative site by Mary Critchley. The authors must feel like Cassandra, explaining exactly what needs to be done and then watching disaster unfold as their advice goes unnoticed by those in authority. Perhaps this will begin to change as the EU begins to recommend vaccination as the method to control and eradicate foot and mouth disease. There is even a letter published in the Times Online by DR COLIN G. FINK which explains

There is a lack of understanding within the vet labs’ scientists of the mechanisms of clinical containment of viral disease.

It may be helpful to the Prime Minister’s Cobra group to read Mary Critchley’s voluntary website www.warmwell.com, to which a number of us contribute.

Warmwell is against the government policy of culling, instead advocating the use of ring vaccination as the best means to contain foot an mouth disease, and because culling does nothing to prevent the spread of bluetongue which is not contagious between cattle.

Second cow in Suffolk

Why on earth has it been culled, we wonder. On whose advice and on what grounds? ..this slaughter is not going to stop the disease. It does not spread from cow to cow and hoping that killing a Highland cow will stop other midges feeding on it and getting infected is absurd. There must be thousands of midges in the area and the fact that bluetongue has only just been noticed means the infected midges have been with us for a fortnight or more. Removing these unfortunate animals is not going to stop the problem.

Well my opinion is that removing the two cattle is not going to help spread the disease either, and since they are either going to die a lingering death or else be rendered unproductive then why take any risk at all by keeping them alive?

Cow without blue tongue

Bluetongue (Blue Tongue or BT) is an infectious but noncontagious, disease caused by a virus whioch is transmitted by midges feeding on the blood of infected animals. The main animals affected are sheep, goats, cattle and deer. Humans and pigs are not affected by blue tongue

Once infected, the outcome can be completely inapparent in many cases, but can also be fatal. In agriculture, Bluetongue Virus (BTV) more often infects cattle than sheep, but the symptoms in sheep are more severe. It is thought that this particular strain in Europe has had mortality rates of 30 per cent in sheep and 10 per cent in cattle. Milk yield in dairy cattle can also drop to 40 per cent and there is evidence that some animals which contracted the virus in northern Europe in the summer of 2006 have suffered impaired fertility.


Bluetongue is thought to have originated in Southern Africa, where it is currently persistent infecting antelope, and other game animals. It has also been observed in Australia, the USA, Africa, the Middle East, Asia and more recently Europe. In Europe it BT has become aregular seasonal occurance in the warmer affected Mediterranean countries, but it subsides if temperatures drop. That’s because midges cannot live below 15 degrees centigrade.

Blue Tongue midge

Then from around October 1998 whether because of climate change or adapatation, the disease began to spread northward. In August 2006, cases of bluetongue were found in the Netherlands, then Belgium, France, Germany and Luxembourg resulting in millions of deaths.

Why is the disease called bluetongue?

The name, as you would probably expect, comes from one of the unfortunate symptoms which include swelling of the head and the neck, lameness, internal bleeding, and ulcers of the mouth, nose and eyes. In mild cases the symtoms can go unnoticed but in some the tongue may turn blue under pressure caused by swelling. That’s where the obvious name comes from.

best method of control

The best way to fight the blue tongue virus, farming experts say, is by vaccination, since slaughtering infected animals does not make sense while midges are responsible for transmitting bluetongue.

Now that the EU Commission is sanctioning vaccination, the UK government vet Debby Reynolds must begin to take notice.

“We consider that vaccination is an important instrument to fight this disease. It isn’t mandatory but we would look favourably on any (EU-27) member state request to apply vaccination,” an EU Commission official said. (reuters)

But the problem for UK farmers is that the particular strain of the virus that has occurred in the northern EU, and has been confirmed as the cause of the two cases so far in the UK is one called “serotype 8” and for this there is no vaccine yet available. However two companies are now developing a vaccine for serotype 8 and this is likely to be available in early 2008. The best hope in the meanwhile is for an early winter cold snap to kill off the midges which transmit bluetongue disease.

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14 Responses to What is bluetongue disease?

  1. Chris Nicholson says:

    Can you tell us if horses can contract Bluetongue please ?

    • Andy Roberts says:

      From my research it is clear that the bluetongue virus does not infect horses or other equine species, but only ruminants such as sheep, goats, cattle, buffalo, deer, antelope and elk.

      However, infected culicoides midges can and do feed on horses, and manure piles are potential breeding sites so horses and stables must be taken into consideration when setting out control measures and restrictions.

  2. Ann Willcocks says:

    I have heard that once an animal is infected an ‘English’ midge could then feed on the infected animal and itself become infected, then off goes the ‘English’ midge and infects more animals. Surely our ‘English’ midges are less susceptible to the cold than their European counterparts? Therefore continuing cases of bluetongue during the year?

  3. Andy Roberts says:

    Well, the subject of midges probably warrants a post to itself but it’s worth posting a quick link to the Scottish “midge forecast”


    and to say that midges in the North of Scotland are a renowned problem for human tourists, but are at their biggest biting nuisance during the summer months. Global warming has been blamed for the increased spread of midges, rather than adaptation to the cold for which they have already had thousands of years. Midges die off after the first hard frost but unfortunately both the midges and the virus somehow overwinter and return the next season.

    See also George Hendry’s book Midges in Scotland

  4. Micky says:

    If someone one hunt and eat the meat of a deer that was infected by this bluetongue would they risk getting sick or anything like that.

    • Andy Roberts says:

      Is the meat from animals infected with bluetongue disease safe for human consumption?

      Yes it is safe, according to DEFRA.

      Bluetongue does not affect humans.

      Neither is the disease spread from vertibrate to vertibrate, only by insect bite so there are no restrictions on meat or meat products from bluetongue areas, only movement restrictions for live animals.

  5. Sarah Wylie says:

    I’m a farmer in central Scotland, and have became increasingly concerned with blue-tongue, as well as foot and mouth…
    I have searched the internet and can’t find any info on the current number of cases of each, which i think is appalling. Last i heard it was at 24 B-T.
    Im curious if anyone knows what the number of cases is, or where i can even find information.
    This year’s been a devastating year for farming with all the flooding, and now this… never mind us scots not being able to sell our lamb, and that resulted in slaughter of them, losing income.
    On top of that sheep farmers are not getting compensation, considering we were promised it! What’s purely sheep farmers mean to do, they’ve lost thousands!

    Sorry to rant, just concerned!

  6. Andy Roberts says:

    Sarah, I’ve heard about the sorry situation of light lambs on the Scottish hillsides, with a proposal to turn them into bio-diesel due to lack of a domestic market. Have they tried the halal slaughter trade I wonder.

    I’ve found where on the DEFRA site they list the number of Blue tongue disease cases it’s here:

    So as at 5:00pm on 12 October 2007 there were 37 confirmed premises affected by Bluetongue. Foot and Mouth disease latest here:

  7. John Davison says:

    Could you please tell me what is the point in DEFRA restricting the movement of cattle & sheep when Blue Tongue disease is not passed from animal to animal ?

    • Andy Roberts says:

      I think the logic goes like this: Bluetongue disease is passed from animal to midge to animal, so if you transported an infected animal into a disease-free region then you could in theory be infecting the local midge population and thus spreading the disease to otherwise healthy stock. The fact that the midges can cover a fair old distance by themselves, possibly even overseas, doesn’t make the situation any better.

  8. Marielle Ford says:

    In South Africa, the same midges cause the dreaded African Horse Sickness which is often fatal and runs for many months through summer. See http://www.africanhorsesickness.co.za

  9. sri says:

    Is there any pictures available of the infected animals that could be posted so that people could be more aware of the disease and vaccines are given to healthy animals but how well is it going to work on animals already infected?

  10. Judi Hewitt says:

    I’m shocked that there’s no sympathy shown to the animals suffering blue tongue. I found a dead lamb in the Welsh hills this week and he looked like he must have really suffered before he died. Although it might not have been blue tongue that killed him, his tongue was very swollen and looked blistered. It looked to me like he’d pushed his face into the crevice of an old wall, presumably because he was looking for some relief from his pain. I pulled him away then took some pics which I intend using in my next “Wales Against Animal Cruelty [WAAC] newsletter. I’ve also alerted Defra about it!
    But please stop thinking of animals in terms of food and profit – it’s inhuman! They have feelings too, though I suppose it takes a certain amount of intelligence to recognise that fact.

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