Ireland stands a fighting chance of getting on top of a potential bluetongue outbreak and stopping it from spreading if suspected cases are reported as soon as they are detected, the Department of Agriculture has said.

Factors in favour of Ireland staying bluetongue-free include geography and the approaching November to March vector-free period, Department senior superintending veterinary inspector for animal welfare Dr Eoin Ryan told Sheep Expo 2024 last week.

“We actually have a chance. We have a more advanced warning, we have the Irish Sea, we may detect it early. It is a reasonable thing to say that if we find bluetongue, we may be able to stop it,” he stated.

In some bluetongue-positive countries, the virus spread so rapidly that the removal of positives was abandoned after cases became widespread.

“We are probably the last country that reasonably has a chance of stopping bluetongue. The Danes had their first case in the beginning of September. It was still very hot and 28 days later they gave up because it had spread across the whole country and they decided [to stop culling] with huge losses.

“The relevance of temperature here is that below 12°C, the virus can’t replicate in the midge. If it is too cold, even if there are midges, the virus can’t replicate in the vector.”

The virus can overwinter in infected animals. While the disease might not spread during colder months, infected livestock act as a source of virus for the following spring.

Bluetongue has had a particularly devastating impact on sheep in the continent. \ Claire Nash

Ryan explained that bluetongue vaccines currently on EU markets in bluetongue areas cannot be used to certify trade as they have undergone a sped-up approval process.

“They don’t stop infection or disease but they do stop animals getting as sick [as they would have been if not vaccinated],” he said.

“They reduce mortality, they reduce sickness, they reduce the amount of virus but they are not fully protective.”

What happens if a case is found in Ireland?

The Department official stated that if bluetongue was confirmed in an animal in Ireland, the course of action would be to “take out the positives, find where the disease may have gone, get ahead of it”.

“The problem is that if bluetongue had been present for three or four weeks and we find it and find infected farms right across the country, which is what happened in some other countries, that would be a very challenging situation.”

Ryan said he could not “nail his colours to the mast” on the exact procedures that would be triggered by the discovery of a case, as much depends on the situation around the case, such as the size of the farm, where it is located in the country and the time of year it is detected.

But in general, the entire herd or flock in which the bluetongue case was discovered would be blood tested for the disease, with positive animals culled.

The disease protocol for bluetongue does not necessitate a blanket cull of all animals as it would for other diseases, such as foot and mouth or bird flu.

Not contagious

However, while the disease is not contagious in spreading from animal to animal directly, a positive case acts as a source of disease for midges to bite and become infected before biting other animals and spreading the disease.

Should the vast majority of a herd or flock test positive, the remaining livestock may be culled as a preventative measure against these showing up with the virus a short time after returning a negative result.

Further follow-up testing would be carried out in the herd or flock, while tracing would be carried out to detect whether animals had potentially been infected before movement to another farm and a movement restriction.

Movement restrictions would be put in place around the farm with intense surveillance in a 150km radius around the farm, as this is the distance midges can travel in the wind.

“Movement bans like this are hugely disruptive and have a huge impact on the business of farming, on animal welfare and on farmers with the stress of it,” Ryan acknowledged.

“I think the impact of bluetongue has been so severe in some of these northern European countries, particularly on their sheep sectors, it is worth that pain in the initial phase for trying to get ahead of it.”