Ulcers start appearing around the mouth, nose and eyes. Then the neck starts to swell, followed by the head. There is lameness. The virus multiplies and soon the beast starts bleeding internally. Breathing becomes more difficult. Death is close.
But this is not foot and mouth. Indeed, there will be few farmers breathing a sigh of relief this weekend as it appears that threat has, for the moment, abated. For they know something potentially as damaging is a mere gust of wind away. Bluetongue is heading this way.
Bluetongue has rampaged north across the Continent, killing 1.8 million animals in less than a decade. This time it is sheep that are the main victims, with the most virulent strains of the virus wiping out up to 70 per cent of infected flocks in two weeks. There is no cure and no vaccine.
For farming communities reeling from BSE and foot and mouth it is the latest nightmare - and thanks to climate change it appears unstoppable.
While it originated in Africa, bluetongue has found its way across the straits of Gibraltar and up to the fields of Holland, Belgium, France and Germany. The reason it has moved so quickly is its carrier: the humble midge.
Yet a variety of the midge has wrought havoc on sheep populations throughout Europe, and experts now say it is unlikely that Britain's 34 million sheep will remain unscathed for much longer.
They expect that following higher temperatures and recent floods it may merely be weeks before the sight of dying animals, with their tongues tinged blue as a result of asphyxiation, greets beleaguered British farmers.
Climate change has ensured that the risk of bluetongue arriving in Britain has never been greater, according to Professor Peter Mertens, head of arbovirus research at the Government's Institute for Animal Health (IAH) in Pirbright, Surrey.
"We have all the elements for an outbreak. Bluetongue has never been in the UK before, so we have a high-risk population with no immunity. It's a serious worry. All it needs is the match to light the fire - the arrival of the virus, via a single infected midge, is all it takes," he warns. " The risk has never been higher ... we are very nervous about it. The real horror story is if we get bluetongue and foot and mouth at the same time."
It is a deadly strain of
bluetongue, known as BTV8, that has found its way from sub-Saharan Africa to northern Europe, and further outbreaks were reported in the Netherlands last week.
For scientists, this is their worst fear realised - that the virus has survived winter and can now live at the same latitude as most of southern England. Now just 100 miles away, bluetongue could cross the Channel in a single day, given the right weather conditions and winds.
Experts now expect the virus to arrive in Britain at any point. Swaths of the countryside will need to be sealed off. The way in which the virus spreads, by midges instead of from animal to animal, means that officials would have to draw up 150km exclusion zones - 15 times the size of the 10km zones used to contain foot and mouth.
And animals could be subject to dusk and dawn curfews, to minimise risks of infection at times of the day when midges are at their most active.
Bluetongue presents no immediate danger to humans, and given the nature of the disease spreads in small clusters as opposed to the rapid sweep foot and mouth can make across the countryside. So the threat is different, but no less pressing, say scientists and farmers.
Nick Blayney, president-elect of the British Veterinary Association, says the symptoms could mean that people mistake it for foot and mouth.
"The symptoms of bluetongue are vague and don't immediately point to the disease, but swelling of the head of neck, ulceration of the mouth, nose and eyes, and lameness are all signs of the disease.
"In the early stages it could be confused with foot and mouth, because of the similarity in symptoms," he says. "The virus multiplies and damages organs, causing internal bleeding and ultimately death - the majority of sheep will die of it in the early outbreaks.
"Bluetongue is right on the edge of the Channel now and it would seem to be a practical consequence of global warming. It is a question of when, rather than if. It is not going to spread dramatically in the same way that foot and mouth can, but the worrying thing is that it will be difficult to stamp out because it is an insect-borne disease."
The bad news for farmers in Kent, Essex and East Anglia is that they are right in the line of fire, with little to protect them but the hope that scientists are able to pick up any signs of the disease in time to stop it from taking hold here.
In a research paper published in the Veterinary Record this year, scientists from the Institute for Animal Health predicted that the summer months leading up to October are the most likely time for bluetongue to cross the Channel - with Britain at risk of easterly winds, which could allow infected midges to be blown across the Channel between four and seven times a month.
The Department for Environment Food and Rural Affairs (Defra) has stated that the potential impact on Britain's agricultural industry would be very high. "An outbreak in the UK could cause severe disease, suffering and losses to the livestock industry, because UK sheep breeds are highly susceptible and have no immunity."
The disease could affect 19 million sheep and nine million cattle, according to government projections. And, unlike with foot and mouth, it could take two years before Britain could become "bluetongue free" and see trade and transport restrictions lifted were an outbreak to occur.
Again, due to the different way the disease spreads restrictions are not as all-encompassing as with foot and mouth. On the Continent, for instance, measures have been restricted to locally affected areas.
But as a precaution, Defra has already banned animal imports from infected zones in the EU as well as imports from unaffected areas that have passed through an infected region. All imports of ruminants (hooved animals that chew the cud) from the EU are being blood tested for signs of bluetongue.
The stakes are high. Unlike foot and mouth, there is no vaccine against BTV8. But the Government predicts that 7.4 million doses of vaccine might be needed, and researchers at the IAH and Merial laboratories in Pirbright are racing to develop one, before the virus arrives here.
Defra has developed a contingency plan to counter the threat of bluetongue and an early-warning system has been put in place, with daily briefings being provided by the Meteorological Office in an attempt to predict when midges might make their way across the Channel.
And scientists at the laboratory controversially linked with the UK's second foot and mouth outbreak in less than a decade have been testing thousands of animals for bluetongue. So far none of the samples, believed to be more than 8,000 since testing began last year, has been positive.
"Right now, because everyone is really quite worried about it, a lot of people are informing the veterinary service about suspect cases," said Professor Mertens. "Even if we don't get it this year, the future doesn't look good - the risk remains."
Defra and the NFU are warning farmers to be on alert for any signs of the virus. Catherine McLoughlin, animal health and welfare policy adviser at the NFU, said: "We are taking this disease very seriously. It could have significant economic impacts in terms of farm losses due to deaths, sickness and reduced productivity, but our main priority right now is actually stopping it from entering the country in the first place."
HSE officials have spent the weekend working around the clock to finish a report into the foot and mouth outbreak, which is expected to be given to the Prime Minister tomorrow.
It will highlight the need to upgrade existing facilities. But with the new super lab not even half-ready, Government officials simply have to hope that new diseases - riding on the wave of climate change - do not succeed in gaining a foothold in Britain.
And although there have yet to be any confirmed cases of bluetongue in Britain, John Gloster, principal research scientist at the Meteorological Office, said that over the last month "there have been a few occasions when everything has gone right - large numbers of midges, temperatures up and the right wind speeds - that could have enabled infected midges to come to the UK."
Bluetongue vs foot and mouth
is the difference between a restriction zone for foot and mouth disease (10km) and that for an outbreak of bluetongue (150km)
can be covered by a midge in a day, given the right weather conditions. Midges normally travel about 1.5-2km in a day
has been budgeted to create a new government laboratory at Pirbright, due to be ready by 2011
sheep in the UK in 2007 - 18 per cent fewer than in 2000, the year before the foot and mouth epidemic