The first case of Bluetongue Disease identified in the UK was a cow in Suffolk. The diagnosis was announced on September 22, 2007. Government scientists have worked out that the virus probably crossed the Channel seven weeks before that, on August 4 or 5, when the wind was right. The common midge which carries the virus, multiplying in its blood-filled stomach, might do a couple of kilometres a day under its own steam. On the wind, it can travel 200, especially over water, and border controls mean nothing to it. That is one reason it is such a worry.

It was around this time in 2007 that the Suffolk farmer began to worry about the cow. He thought she might have foot and mouth. The first symptoms are similar – drooling, possibly lameness, raised temperature, discharges from eye and nose, swollen tissues, mouth ulcers. A blue tongue might come later, if the swelling of the head tissues continues.

We can thank our gods that it was not foot and mouth. But it could have been almost as bad. It was in Belgium, for example, where 70 per cent of some flocks of sheep died from Bluetongue after it hit in 2006.

For once, most farmers have some praise for the Department for Environment Food & Rural Affairs. In the run-up to the UK outbreak, the new Secretary of State at Defra, Hilary Benn, was briefed on the options. One was the promise of a vaccine, which the drugs companies had been working on since it became clear that a strain of Bluetongue – BTV8 – had got into northern Europe, where the animals had no inherited immunity.

It was still unclear how well it would work and it still had to be worked out who would pay for it. But Benn announced, last December, that Defra would guarantee an order for 22 million doses. France made a similar commitment. Other countries followed suit later.

Alasdair King, a spokesman for Intervet, which was first in the field and has supplied most of Europe's vaccine, said yesterday: "It would normally take 5-12 years to get a product like this developed and licensed. By pulling all the stops out, and with the co-operation of the English and French authorities in particular, we did it in two, counting from the time we identified BTV8. But we needed those early assurances that we were going to get something out of it."

The vaccine gives us a good chance of containing Bluetongue and a slim chance of wiping it out. The odds will be re-assessed at the end of this month. It has not been a good summer for the midges but they are now beginning to multiply – and Bluetongue is already spreading again in France, where the climate is a month ahead of ours.

So far this year, there has not been a Bluetongue case in this country which could not be explained away either as an import – cattle breeders are swapping stock across the Channel all the time – or as a hangover from one of last year's midge bites. But we will be lucky if there are not fresh cases this month. Nobody knows quite where the virus goes in the winter, after the midges die, but it lives on somehow – possibly in the midge's eggs; possibly in some wild animal which shows no symptoms.

The second Bluetongue case in Suffolk was announced the day after the first. The fourth and the fifth followed quickly. A month later, the virus was in Cambridgeshire and Kent. In March this year, before a midge had moved, it popped up in cattle at Alford, Lincolnshire, 10 miles inland from Skegness. That meant a new "protection zone" and outside that a new "surveillance zone", which stretched into Yorkshire, and made Bluetongue come alive in terms every farmer could understand – money lost at sale time, because animals could not always go to the best markets.

Up to yesterday morning, there had been 141 confirmed cases in England and most of them are being put down to midge bites last year. The disease can be spread by poor hygiene with needles and so on but it does not normally jump from animal to animal without incubating in a midge first. That much is known. But there is still a lot to learn. The disease behaves differently in different breeds
of sheep, for example, and we have sheep types not found anywhere else.

Bluetongue only affects cud-chewers like cattle, sheep, goats, deer, alpaca and camels. Sheep are most likely to die. Cattle can be carriers without showing symptoms.

At the end of April, the cavalry arrived. The first batch of vaccine was available. It would cost 50p-£1 for one shot, enough to immunise a sheep. Cattle would require two shots, three weeks apart. They would need the same again next year, and possibly another set of shots if a new strain of Bluetongue took hold. But compared with the potential losses, the costs looked okay. An unprecedented vaccination programme began.

So as to waste no time arguing, it was made voluntary in England – and Wales followed suit. In the zones closest to the outbreaks, up to 80 per cent of animals were treated. The figure dropped a bit after that and Bluetongue might still find a way through. But at least there would be a limit on the consequences. Once the first protection zones had had their supplies, new ones were created, with new surveillance zones adjoining. This shifting of boundaries, and the rules about moving between zones, have caused problems for markets and shows all summer and farmers have questioned the logic of the movement restrictions. One week it was against the law to take animals from Doncaster to Driffield and back. The next it was okay, even though vaccination had not started in Driffield.

Defra could only say: those are the rules. It was agreed at European level that vaccination could take place only in an official protection zone. If the system threw up some illogicalities, they would be discussed later. Officials wished we would spare a minute to recognise what had gone right.

It is now, touching wood, the time to do that. The last new Bluetongue victims, in Devon, apparently brought it in from abroad. The last pieces of Defra's vaccination jigsaw are being completed, in Northumberland and Cumbria.

Kate Sharpe, who manages Defra's veterinary division, Animal Health, over most of Yorkshire, summed up yesterday: "It was very forward-looking to order the vaccine at the point we did. And the roll-out has worked extremely well. In effect, we have got a year of precautionary work in before the next advance by the midges. But we are approaching a high risk time, so the message to farmers remains the same: be vigilant and don't hesitate – vaccinate."

The celebrations at Defra have turned the spotlight on an unforeseen consequence of devolution. The Scots decided to wait for the winter months before they even started vaccination, because they intended to make it compulsory, and it would be easier then. Now their farmers face difficulties selling unvaccinated animals into England and English movements into Scotland will become very difficult now that all of our side of the border is officially "dirty" – meaning bluetongue is a recognised threat – and theirs is still "clean". Even after vaccination, there are restrictions on moving animals across zone boundaries – especially if they are pregnant, which many will be.

Yesterday, the Scots announced that animals would be allowed
to move their way as long as they were going direct to slaughter. But that still leaves problems for the trade in breeding stock. Behind the scenes, there are demands for heads to be banged together in time for better co-ordination next year.

Meanwhile, Kate Sharpe and her colleagues are hoping for an old-fashioned long cold winter. There is just a faint chance it would take us back to the position we were in before that fateful wind blew across the Channel last August.

Any suspected Bluetongue case should be reported to the divisional Animal Health office on 0113 230 0100.