The likelihood of Irish cattle being exposed to bluetongue virus serotype 3 (BTV3) in the coming season is now much higher than it has been previously.
This is as a result of bluetongue being identified in the southeast of the country last month and given the number of cases in England and Wales, UCD’s herd health group has said.
There are two potential sources from which Irish herds and flocks could become infected in 2026, it outlined.
The first is “overwintering” of the current incursion and emergence of infection from the current sites in Co Wexford, and the second is transmission following a second introduction via windborne spread (or animal introduction) from the UK or mainland Europe.
The precise mechanism for overwintering of bluetongue is unclear; however, the chances of the infection successfully overwintering and acting as source(s) of infection for the 2026 season increases as further infected farms are identified.
In addition, given the extent and geographical distribution of bluetongue now in the UK, “it seems likely that we will see subsequent windborne incursions seeding infection from England and Wales, as well as other potential sites”, the group warned.
Potential impacts
Deciding on the appropriate actions for Irish farmers is a key consideration for 2026, the group maintained.
“At present, vaccination is the only evidence-based control option available to farmers now at risk of exposure. In addition to assessing exposure risk, the decision as to whether to vaccinate or not in 2026 requires considering the likely impacts of infection should the herd become infected,” it added.
For Irish farmers, the most important factors are likely to be potentially large fertility impacts
In terms of production, the group said that the reported impacts are potentially significant.
“For Irish farmers, the most important factors are likely to be potentially large fertility impacts (embryonic death, bull infertility and abortion); congenital defects (principally hydranencephaly) and perinatal mortality in calves infected in utero; increased mortality rates in all age groups; lameness; and decreased milk yield.
“It is important to note that there is variation in the severity and duration of clinical signs reported by different countries that have already been affected, and between different farms in the same country,” it warned.
In the Netherlands, Belgium and France, mortality and fertility impacts have been dramatic in both cattle and sheep. In the UK however, although there have been fewer formal reports of disease impact, there are indications that the observed clinical and production impacts have been substantially less than those documented in other European countries.
Uncertain
How this apparent reduced impact in UK livestock might have occurred is not yet clear, the group said.
Bluetongue being found in the southeast of the country has increased the chance of cattle being exposed to the virus this summer.
“As a result, the likely impact of the disease in Ireland, even in the case of the infection becoming established in 2026, is uncertain.
“However, in discussing the risk posed by BTV 3 with farmers, it is worth noting that our dairy herds and spring-calving suckler herds could be especially vulnerable to BTV 3 impacts.
“This is because the time of highest vector activity (June to September) aligns with the point at which much of the national cattle herd will be in early to mid-gestation,” it warned.
Studies show that bluetongue infection at this point of gestation is associated with embryonic death and congenital defects in calves.
“Due to the substantial consequences of even minor reductions in reproductive performance to short- and long-term profitability of spring-calving systems, losses for individual herds could be substantial should the infection enter the herd during this time,” the group said.
It advised that farmers talk to their vets in advance of the 2026 breeding season.
Bluetongue virus was first detected in Irish cattle on 22 January in the Blackwater area of Co Wexford.
Read more
Ban on cross-border livestock trade to stay
Bluetongue and lambing – what to look out for
Over 1,500 cattle and sheep on farms where bluetongue was found
The likelihood of Irish cattle being exposed to bluetongue virus serotype 3 (BTV3) in the coming season is now much higher than it has been previously.
This is as a result of bluetongue being identified in the southeast of the country last month and given the number of cases in England and Wales, UCD’s herd health group has said.
There are two potential sources from which Irish herds and flocks could become infected in 2026, it outlined.
The first is “overwintering” of the current incursion and emergence of infection from the current sites in Co Wexford, and the second is transmission following a second introduction via windborne spread (or animal introduction) from the UK or mainland Europe.
The precise mechanism for overwintering of bluetongue is unclear; however, the chances of the infection successfully overwintering and acting as source(s) of infection for the 2026 season increases as further infected farms are identified.
In addition, given the extent and geographical distribution of bluetongue now in the UK, “it seems likely that we will see subsequent windborne incursions seeding infection from England and Wales, as well as other potential sites”, the group warned.
Potential impacts
Deciding on the appropriate actions for Irish farmers is a key consideration for 2026, the group maintained.
“At present, vaccination is the only evidence-based control option available to farmers now at risk of exposure. In addition to assessing exposure risk, the decision as to whether to vaccinate or not in 2026 requires considering the likely impacts of infection should the herd become infected,” it added.
For Irish farmers, the most important factors are likely to be potentially large fertility impacts
In terms of production, the group said that the reported impacts are potentially significant.
“For Irish farmers, the most important factors are likely to be potentially large fertility impacts (embryonic death, bull infertility and abortion); congenital defects (principally hydranencephaly) and perinatal mortality in calves infected in utero; increased mortality rates in all age groups; lameness; and decreased milk yield.
“It is important to note that there is variation in the severity and duration of clinical signs reported by different countries that have already been affected, and between different farms in the same country,” it warned.
In the Netherlands, Belgium and France, mortality and fertility impacts have been dramatic in both cattle and sheep. In the UK however, although there have been fewer formal reports of disease impact, there are indications that the observed clinical and production impacts have been substantially less than those documented in other European countries.
Uncertain
How this apparent reduced impact in UK livestock might have occurred is not yet clear, the group said.
Bluetongue being found in the southeast of the country has increased the chance of cattle being exposed to the virus this summer.
“As a result, the likely impact of the disease in Ireland, even in the case of the infection becoming established in 2026, is uncertain.
“However, in discussing the risk posed by BTV 3 with farmers, it is worth noting that our dairy herds and spring-calving suckler herds could be especially vulnerable to BTV 3 impacts.
“This is because the time of highest vector activity (June to September) aligns with the point at which much of the national cattle herd will be in early to mid-gestation,” it warned.
Studies show that bluetongue infection at this point of gestation is associated with embryonic death and congenital defects in calves.
“Due to the substantial consequences of even minor reductions in reproductive performance to short- and long-term profitability of spring-calving systems, losses for individual herds could be substantial should the infection enter the herd during this time,” the group said.
It advised that farmers talk to their vets in advance of the 2026 breeding season.
Bluetongue virus was first detected in Irish cattle on 22 January in the Blackwater area of Co Wexford.
Read more
Ban on cross-border livestock trade to stay
Bluetongue and lambing – what to look out for
Over 1,500 cattle and sheep on farms where bluetongue was found
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