Why are we asking this now?

It started with Debbie . . . a Highland cow on a farm near Ipswich in the UK which was confirmed last week as Britain's first case of bluetongue disease, a lethal virus which has killed millions of farm animals in northern Europe. Since then, three more cases have been discovered in the UK, leading to fears an outbreak in that country is imminent. Now there are real fears among Irish farmers that the disease could reach this country, causing untold damage to our agriculture and economy.

What exactly is bluetongue disease?

It is caused by a deadly virus that mainly affects sheep but can also infect cattle, goats, deer and other ruminants. Symptoms include swelling of the head and the neck, lameness, internal bleeding and ulcers of the mouth, nose and eyes. The tongue may turn blue under pressure created by the swelling, giving the disease its name. The virus has infected nearly 3,000 animals in northern Europe since July, where the death rate has been about 30%.

Unlike foot-and-mouth, it does not spread from animal to animal but is instead transmitted by midges, which bite an infected animal and then transfer the virus to an uninfected one.

Where has it come from?

There have been a series of outbreaks of bluetongue in the Netherlands, Belgium, western Germany and northern France since August 2006. The virus has infected nearly 3,000 animals in northern Europe since July. The type of virus identified in the infected cows in the UK has been confirmed as the same as that circulating in northern Europe . . . serotype 8. The virus originated in southern Africa, where it is spread by a different species of midge.

Global warming has been blamed for its spread north to the Mediterranean and southern Europe and then to northern Europe.

What are the chances of it arriving here?

No one can say for sure . . . the midge responsible for spreading the virus in northern Europe is the Culicoides species, which is capable of flying 1.5 to 2km a day. It mainly depends on the weather. If it remains mild long enough for the midges to thrive and wind direction takes them in a westerly direction across the Irish Sea, then we're in for it. But as temperatures here continue to drop, hopes have continued to rise. If we get a good cold snap soon (as Met Eireann has predicted), we may escape.

"We are helpless and at the mercy of nature, " said Irish Cattle and Sheep Farmers' Association president Malcolm Thompson. "You cannot put a mosquito net over the Irish Sea. We are in the lap of the wind and weather."

What are we doing to prevent it getting to Ireland?

Because of the outbreak of foot-and-mouth disease in the UK, Irish ports and airports were already closed to livestock from Britain and, needless to say, this plan will remain in place until any danger has passed.

While admitting there is an "increased likelihood" Bluetongue disease could make its way here, minister for agriculture Mary Coughlan has updated contingency plans and prepared advice leaflets for vets and farmers. She has also commissioned a study from NUI Galway into patterns in the spread of the disease via midges but this will not be ready for three years.

Farmers' groups and the opposition have complained Ireland is inadequately prepared for the disease. According to Fine Gael fisheries and food spokesman Michael Creed, a national biosecurity committee is needed to deal with the double threat of bluetongue and foot-and-mouth disease.

"Changing environmental conditions present issues for both livestock and public health and such a committee could ensure we have the highest level of biosecurity, the most up-to-date scientific data and the expertise to prepare for emerging risks, " he said.

What can we expect if bluetongue arrives in Ireland?

According to Teagasc: "An outbreak in Ireland would have a significant economic impact in terms of farm losses due to death and reduced productivity, along with losses in export revenue."

Nine in 10 Irish cattle are exported, so any ban on Irish exports would hit the industry extremely hard, as foot-and-mouth did in 2000.

"With an 8bn agri-food export sector from this country, the implications of a serious disease and outbreak are much more serious for Ireland than Britain, " said IFA president Padraig Walshe. Because sheep are also vulnerable to bluetongue disease, its arrival here could well be the "final straw" for the Irish sheep industry, according to farmers.

If it does arrive, what measures can be taken?

Mass slaughter to eradicate bluetongue disease is not an option as that will not eliminate the midges. The only control measures that would be available to farmers would be to spray insect breeding sites such as manure heaps with insecticide, and douse livestock with insect repellent to reduce the number of midge bites. But these measures would at best reduce the level of infection rather than eliminate it.

Keeping animals in sheds at dawn and dusk, when the midges are out in force, has not been shown to be effective. The only other defence is vaccination. But there are currently no effective vaccines against bluetongue in Europe. Vaccines developed for use in sheep in South Africa, where the disease originated, cause severe side effects in European breeds.

European versions of the vaccine have made the problem worse because the live virus used in the vaccine has combined with the circulating virus to create new strains. But a vaccine based on an inactivated virus is being developed and is expected to be ready by next summer, so if Ireland does escape this winter, we could be in the clear for good.

Are we worrying about nothing?

Possibly. Midges can't survive below 150C and most experts are pinning their hopes on the fact the Ipswich case happened at the end of the summer rather than the beginning. Met Eireann is predicting temperatures close to freezing this weekend, so that will certainly reduce any risk of the disease getting here. And if the vaccine is finalised by next summer, we may never be at risk. All the same, if it does arrive, it cannot be denied that bluetongue disease will have a devastating effect in our country.