The detection of bluetongue in animals on Co. Wexford farms does not mean that midges can currently spread the disease in the area, but farmers should talk to their local vet about potentially vaccinating animals before the summer season.

That's according to the deputy chief veterinary officer (CVO) at the Department of Agriculture, Food and the Marine (DAFM), Prof. Eoin Ryan, who spoke to Agriland on the AgriFocus podcast.

He explained that the animals which were first detected as having bluetongue in Wexford were most likely bitten in late autumn, when temperatures were milder, and it was antibodies to the virus that were then detected as part of stringent routine testing more recently.

The offending midge, which was probably blown across the Irish Sea from England or Wales, even if it survived until now (which is probably unlikely), would not be able to spread the virus at such low current temperatures.

In order for midges to spread bluetongue, temperatures need to be consistently about 12°C.

"We've detected an incursion which probably happened a couple of months ago, maybe three months ago, we can't put a time on it right now," Prof. Ryan said.

"The implication of it being detected now is, because the virus cannot spread through midges right now, it's too cold, that actually means there isn't a requirement to put in place stringent movement controls that would have been required if this was July or August."

Bluetongue vaccine

The deputy CVO has said there are contingency plans in place for movement controls to prevent the spread of bluetongue but that such measures are not needed yet "because it's the depths of January".

"It's not necessary right now; it wouldn't give us any advantage," he explained.

The consideration livestock farmers will have to give time to over the coming months is whether or not to avail of the vaccine, something that is not as clear cut as just deciding yes or no.

The deputy CVO explained that it will come down to each individual farm enterprise on whether the cost would be worth the benefit and has advised farmers to speak to their local vet before the onset of the summer warmer season from about May.

"Vaccination for bluetongue has been authorised in Ireland since just before Christmas. There are three authorised vaccines in the EU for bluetongue-3," Prof. Ryan said.

"We encourage farmers to have a conversation with their vet about whether vaccination is the right choice for them because, of course, these vaccines aren't free, you've to buy them and it depends on the business."

He cited examples such as pedigree sheep or cattle breeders who might want the vaccine as they are very concerned about the potential impact on the flock or herd should bluetongue reach them; other farmers might decide to forego the vaccine due to the cost and take their chances and hope not to have an outbreak of infection.

"There is no need to rush to vaccinate now; the time you would want to have the vaccine delivered, if you were going to vaccinate, is by the high-risk summer period," the deputy CVO said.

"So that's starting around May-ish... is when we would expect the virus start to spread if it is still here then. So there are several months during which [farmers] can have that conversation, discuss with their vet and their vet can apply for a licence to get this vaccine."

The DAFM has confirmed from suppliers that there are currently stocks of the vaccine available in Ireland and therefore it doesn't anticipate any supply issues.

Bluetongue virus

Bluetongue is a viral disease that affects cattle, sheep, goats and camelids such as alpacas and llamas.

The virus can cause animals to get quite sick with a range of clinical signs such as :

Swollen tongue with reddish appearance (hence the bluetongue name);
Difficulty breathing;
Lameness;
Pregnant animals may abort;
Crusty erosive lesions around mouth/gums/lips.

In general it does not kill big animals, but it can make them quite sick. In other animals they may not show any clinical signs at all, such as the case in Wexford.

The virus is transferred mainly by biting midges.

How transmission spreads is if an animal may be infected with bluetongue, a midge bites that animal, the midge itself then becomes infected and a period of time later, when the midge has completed its cycle, if that midge goes on to bite other cattle or sheep, it passes on the infection.

The deputy CVO has highlighted the important difference between a virus like bluetongue and other diseases such as foot and mouth disease (FMD).

Bluetongue it not directly transmittable from animal to animal, it's insect borne.

However in terms of breeding it can be spread via infected semen or embryos, so e.g., if a bull became infected, its mated cows can then become infected.

Also, if pregnant animals become infected, it can be passed on to the lamb or calf for instance.

Up until recently, Ireland was the only country in west or north Europe to retain bluetongue-free status, however that freedom has not been lost as a result of the detections in Wexford.

"Those results will be useful; they will give us a bigger picture, but we're not going back to bluetongue freedom any time soon."

It was confirmed today that three more herds have been detected as having bluetongue in Wexford.

You can listen to the AgriFocus podcast on bluetongue in full by clicking here.