With vets investigating a possible case of bluetongue in Co. Down, here is an overview of the virus and what Irish farmers should look out for.

Bluetongue virus (BTV) can infect cattle, goat, sheep and wild ruminants (such as deer) as well as camelids (such as alpaca).

The disease does not affect humans, nor does it impact on food quality (e.g., meat and milk). However, it can impact animal health, and as a result, the finances of livestock owners.

Cows infected with bluetongue can show symptoms of fever, lameness, respiratory disorders, drooling, facial swelling, and cyanosis of the tongue.

In some cases, strains can cause stunted growth, death, and abortions in infected animals.

Sheep are more likely to show symptoms and signs of bluetongue than cattle. Unfortunately, this means that the illness is harder to detect in cattle, which can make it more likely to spread.

Origins

The first reported cases of bluetongue were in South Africa over 100 years ago. Following that discovery, it spread northwards in subsequent decades, possibly due to growing international trade and global warming.

The disease can now be found on almost every continent (Antarctica being the exception).

Its arrival in Northern Europe (Germany, Belgium, The Netherlands, then France) dates to 2006.

In 2023, a new type (serotype 3) of bluetongue arrived in Europe. While it largely affects sheep, recent cases in the UK involve cattle.

How it travels

According to the Department of Agriculture, Food and the Marine (DAFM): “Bluetongue virus is spread by infected biting midges (Culicoides species) which are present in Ireland and are generally most active between April and November.

“Midge activity reduces in colder temperatures.”

Higher temperatures result in both a rise in midge activity and in the ability for the bluetongue virus to replicate.

However, while the most active months are typically April to November, suspected cases have been detected on the island of Ireland over the weekend.

Because the virus travels via the midge population, eradication can be difficult.

Bluetongue risk to Irish farmers

Ireland entered a higher risk period for bluetongue in summer 2025, due to the following factors:

Increased temperatures in summer, making it more likely for the virus to replicate and spread;
The virus spreading across much of England and other parts of the UK;
A risk from imported livestock, even though controls and restrictions are in place.

For farmers who might be buying livestock from Europe, there is a risk that animals may not meet certification requirements to Ireland, due to disease outbreaks, according to DAFM

This risk is also present when it comes to the importing of embryos or semen.

In addition, when buying livestock from a European country, there is a risk the animals may be impacted by bluetongue in the country of origin or during their journey.

Also, farmers should note that DAFM “will not pay compensation for any imported animals which subsequently test positive for bluetongue post-entry into Ireland”.

So, before animals leave their country of origin, DAFM encourages farmers to make sure they are BTV-free by requesting a premovement test for the virus.

While timings can vary, the incubation period of bluetongue is approximately one to two weeks.

Early detection

With a suspected case on this island, Irish Creamery Milk Suppliers' Association ICMSA president Denis Drennan said the government and industry players "must make this their priority in the coming weeks".

"Everyone needs to be extra cautious in the coming weeks and farmers should contact their vet if they have any concerns about their own animals," Drennan said.

Meanwhile, the Ulster Farmers' Union (UFU) has issued a statement following a meeting with the veterinary division of the Department of Agriculture, Environment and Rural Affairs (DAERA).

UFU president William Irvine said: "Our priority is to stay fully informed as DAERA's investigations progress and to ensure members receive accurate updates as more information becomes available."