The identification of further cases of the bluetongue virus on farms in Wexford has raised significant concern among farmers, with sheep farmers particularly worried. These fears are borne out by the devastating effect of the disease on sheep flocks in the Netherlands, Belgium and Germany.
A research paper looking at the impact of bluetongue serotype 3 outbreak on sheep and goat mortality in the Netherlands in 2023 lay bare the high level of mortality possible. As detailed in Table 1, the disease is thought to be responsible for the death of 55,000 sheep in a period of less than four months from week 36 to week 52 in 2023.
This equates to almost 5% of the national flock dying in a short period of time with over 5,500 flocks affected. This increased to over 10,000 farms (cattle and sheep) recording infection in their animals in 2024. The use of vaccination did not prevent infection but it is said to have reduced mortality.
It is worth highlighting that the disease coincided with ideal conditions for spread of the virus with high temperatures allowing for rapid replication of the virus in the midge population and extremely high rates of infection in certain regions. This gave rise to mortality on individual farms of 50% to 70% of the flock.
Some farmers opted to house animals thinking that it may help protect their stock but it compounded issues in poorly ventilated buildings with midge activity high and animals in close confinement.
Severity of disease
The severity of disease in these flocks meant that sheep quickly succumbed to the virus. The clinical symptoms most apparent were oedema quickly setting in, with swelling of the head, high temperatures, nasal discharge and lesions appearing on areas such as the mouth, nose and feet of animals.
Such animals quickly became lethargic, often standing with a hunched back or reluctant to stand or move and drooling from their mouth. Secondary infections set in, with animals also experiencing respiratory challenges. A paper published in the British Veterinary Association’s In Practice Journal in May 2024 highlighted that the severity of disease and prognosis for animals exhibiting serious clinical symptoms was so poor that early euthanasia was a common outcome.
Similar devastating effects were witnessed in certain regions in Germany and France while the Belgian sheep sector has been combating the virus for a couple of decades.
The latest data published by the European Commission show that for the period January to October sheep output in Germany fell by 36.2% compared to the EU average of 5.8%. The disease hit in 2023 and spread nationwide in 2024 causing severe losses in sheep and cattle, which in turn curtailed output in 2024.
Midge activity
It is no surprise that bluetongue virus was a topic attracting keen interest at last week’s Cattle Association of Veterinary Ireland (CAVI) sheep health event for veterinary practitioners. The topic was touched upon by Joseph Angell, UK veterinary specialist and addressed in detail by Dr Eoin Ryan, deputy chief veterinary officer at the Department of Agriculture.
In outlining the challenge of combating the spread of the virus given the right environmental conditions, Ryan highlighted how midge bites can be in their thousands per animal per night during peak midge activity.
A single bite from a bluetongue-infected midge is enough to transmit the virus so it is easy to see that when there is a high population of infected midges how the disease can spread rapidly during peak midge activity and a high infection load in the environment.
There is no way of preventing midge activity, with insecticides and repellents noted as not being effective at preventing transmission. The only method of boosting an animal’s defence is vaccination.
Abortion and foetal deformities
The severity and rapid onslaught of disease in sheep infected has meant that one of the virus’s symptoms, abortion, has not been regularly seen in outbreaks.
The research paper published in response to the outbreak in the Netherlands in 2023 stated that abortion and foetal deformities had not been seen and were possibly not a symptom of BTV 3, with a similar experience reported in other regions.
While abortion was not frequent in sheep it was a common clinical symptom seen in bovines with dairy herds in particular experiencing significant levels of abortion in 2024.
This pushed calving dates back and contributed to the spike in milk production experienced in continental Europe in autumn 2025 which put further downward pressure on farmgate returns.
The reason why abortion was seen more in cows and not in ewes is that cattle can better withstand the virus, often showing no clinical signs of disease.
This has been apparent in the cases identified in Ireland to-date with the initial case identified through abattoir testing via the cull cow serosurveillance programme with further cases identified through surveillance testing.
The experience from continental European countries has also highlighted the possibility of calves being born with congenital deformities and so-called “dummy calves”.
The latter is caused by the absence of cerebral hemispheres with animals often appearing lifeless or blind.
Some die immediately while others survive for a few weeks. This is similar to the experience of the Schmallenberg virus which first hit in 2012 and has occurred sporadically since then.
Lambing challenges
The same challenge faces sheep but the fact that the virus is typically so aggressive and that sheep succumb to the virus and suffer a greater level of infection than cattle means that the birth of malformed foetuses or congenital deformities is rarely seen.
This is not to say that it doesn’t occur and farmers experiencing high levels of unexplained barrenness are advised to speak with their vet regarding the submission of blood samples for analysis. Any cases of malformed foetuses or the birth of “dummy” like lambs should also be reported immediately so that follow-up testing can take place. This may be a higher possibility at a low level of infection.
There is little evidence available to determine the likelihood of abortion, malformed foetuses etc depending on the stage of pregnancy that an animal is infected and this is particularly true of sheep.
It is important to note that as the virus can pass through the placenta calves or lambs can be born infected and spread a new wave of infection. This is another reason why vigilance around biosecurity is required if purchasing pregnant animals.
Likely prevalence
It is impossible to predict the spread and prevalence of bluetongue virus in 2026. The spread of the virus is strongly influenced by weather as touched upon already. The current temperatures are too low for replication of the virus in midges. This can only occur when temperatures are above 12°C.
Therefore in an Irish context the main risk period is from June to September with May and October possibly lower risk depending on temperatures.
The experience of the virus in Britain could possibly be giving a false sense of security with some breeders citing that the virus has been present in Britain for over a year without doing substantial damage
As mentioned already the higher the temperature the shorter the incubation period will be in a midge. This varies from four to 20 days. Once a host, eg sheep or cattle, is infected viremia or infection establishes within two to four days with that host then capable of passing on the infection to a healthy midge.
The experience of the virus in Britain could possibly be giving a false sense of security with some breeders citing that the virus has been present in Britain for over a year without doing substantial damage.
This is also influencing the rate of uptake of vaccination options which have been low to date. Hopefully this will not materialise but there is nothing to predict if this will remain the case or if there will be a significant spike in cases in summer. The same can be said of cases in Wales, Northern Ireland and now Wexford with the likelihood that further cases will be identified through surveillance testing.
Notifiable disease and culling policy
Bluetongue virus is a notifiable disease, meaning that a farmer is obliged to report its presence to the Department of Agriculture.
This can be completed by phoning your regional veterinary office or out-of-hours contacting the National Disease Emergency Hotline on 01-4928026.
One of the most common questions asked in the last week is what will happen in the case of the virus being suspected and if animals will be culled. The first step is a veterinary investigation with the suspect animals and herd/flock cohorts sampled. The individual herd/flock will also be restricted. There is no definitive decision on the culling of animals.
The Department advised vets this week that culling decisions will depend on epidemiological circumstances, which includes the prevalence, distribution and health of animals, the time of year and local spread of disease.
The current position is that culling is unlikely as temperatures are too low for the spread of infection but this approach will remain under constant review.
In brief
The main symptoms of disease in sheep are oedema of the head, poor or no appetite, lethargy, lesions on the mouth, nose and coronary band and discharge from the nose, salivating from the mouth.Abortion can also occur while the birth of mummified or malformed foetuses is rare in sheep but possible.Farmers should remain vigilant for any signs of disease and report any suspect cases immediately. It is impossible to predict the likelihood of the disease spreading and prevalence levels.
The identification of further cases of the bluetongue virus on farms in Wexford has raised significant concern among farmers, with sheep farmers particularly worried. These fears are borne out by the devastating effect of the disease on sheep flocks in the Netherlands, Belgium and Germany.
A research paper looking at the impact of bluetongue serotype 3 outbreak on sheep and goat mortality in the Netherlands in 2023 lay bare the high level of mortality possible. As detailed in Table 1, the disease is thought to be responsible for the death of 55,000 sheep in a period of less than four months from week 36 to week 52 in 2023.
This equates to almost 5% of the national flock dying in a short period of time with over 5,500 flocks affected. This increased to over 10,000 farms (cattle and sheep) recording infection in their animals in 2024. The use of vaccination did not prevent infection but it is said to have reduced mortality.
It is worth highlighting that the disease coincided with ideal conditions for spread of the virus with high temperatures allowing for rapid replication of the virus in the midge population and extremely high rates of infection in certain regions. This gave rise to mortality on individual farms of 50% to 70% of the flock.
Some farmers opted to house animals thinking that it may help protect their stock but it compounded issues in poorly ventilated buildings with midge activity high and animals in close confinement.
Severity of disease
The severity of disease in these flocks meant that sheep quickly succumbed to the virus. The clinical symptoms most apparent were oedema quickly setting in, with swelling of the head, high temperatures, nasal discharge and lesions appearing on areas such as the mouth, nose and feet of animals.
Such animals quickly became lethargic, often standing with a hunched back or reluctant to stand or move and drooling from their mouth. Secondary infections set in, with animals also experiencing respiratory challenges. A paper published in the British Veterinary Association’s In Practice Journal in May 2024 highlighted that the severity of disease and prognosis for animals exhibiting serious clinical symptoms was so poor that early euthanasia was a common outcome.
Similar devastating effects were witnessed in certain regions in Germany and France while the Belgian sheep sector has been combating the virus for a couple of decades.
The latest data published by the European Commission show that for the period January to October sheep output in Germany fell by 36.2% compared to the EU average of 5.8%. The disease hit in 2023 and spread nationwide in 2024 causing severe losses in sheep and cattle, which in turn curtailed output in 2024.
Midge activity
It is no surprise that bluetongue virus was a topic attracting keen interest at last week’s Cattle Association of Veterinary Ireland (CAVI) sheep health event for veterinary practitioners. The topic was touched upon by Joseph Angell, UK veterinary specialist and addressed in detail by Dr Eoin Ryan, deputy chief veterinary officer at the Department of Agriculture.
In outlining the challenge of combating the spread of the virus given the right environmental conditions, Ryan highlighted how midge bites can be in their thousands per animal per night during peak midge activity.
A single bite from a bluetongue-infected midge is enough to transmit the virus so it is easy to see that when there is a high population of infected midges how the disease can spread rapidly during peak midge activity and a high infection load in the environment.
There is no way of preventing midge activity, with insecticides and repellents noted as not being effective at preventing transmission. The only method of boosting an animal’s defence is vaccination.
Abortion and foetal deformities
The severity and rapid onslaught of disease in sheep infected has meant that one of the virus’s symptoms, abortion, has not been regularly seen in outbreaks.
The research paper published in response to the outbreak in the Netherlands in 2023 stated that abortion and foetal deformities had not been seen and were possibly not a symptom of BTV 3, with a similar experience reported in other regions.
While abortion was not frequent in sheep it was a common clinical symptom seen in bovines with dairy herds in particular experiencing significant levels of abortion in 2024.
This pushed calving dates back and contributed to the spike in milk production experienced in continental Europe in autumn 2025 which put further downward pressure on farmgate returns.
The reason why abortion was seen more in cows and not in ewes is that cattle can better withstand the virus, often showing no clinical signs of disease.
This has been apparent in the cases identified in Ireland to-date with the initial case identified through abattoir testing via the cull cow serosurveillance programme with further cases identified through surveillance testing.
The experience from continental European countries has also highlighted the possibility of calves being born with congenital deformities and so-called “dummy calves”.
The latter is caused by the absence of cerebral hemispheres with animals often appearing lifeless or blind.
Some die immediately while others survive for a few weeks. This is similar to the experience of the Schmallenberg virus which first hit in 2012 and has occurred sporadically since then.
Lambing challenges
The same challenge faces sheep but the fact that the virus is typically so aggressive and that sheep succumb to the virus and suffer a greater level of infection than cattle means that the birth of malformed foetuses or congenital deformities is rarely seen.
This is not to say that it doesn’t occur and farmers experiencing high levels of unexplained barrenness are advised to speak with their vet regarding the submission of blood samples for analysis. Any cases of malformed foetuses or the birth of “dummy” like lambs should also be reported immediately so that follow-up testing can take place. This may be a higher possibility at a low level of infection.
There is little evidence available to determine the likelihood of abortion, malformed foetuses etc depending on the stage of pregnancy that an animal is infected and this is particularly true of sheep.
It is important to note that as the virus can pass through the placenta calves or lambs can be born infected and spread a new wave of infection. This is another reason why vigilance around biosecurity is required if purchasing pregnant animals.
Likely prevalence
It is impossible to predict the spread and prevalence of bluetongue virus in 2026. The spread of the virus is strongly influenced by weather as touched upon already. The current temperatures are too low for replication of the virus in midges. This can only occur when temperatures are above 12°C.
Therefore in an Irish context the main risk period is from June to September with May and October possibly lower risk depending on temperatures.
The experience of the virus in Britain could possibly be giving a false sense of security with some breeders citing that the virus has been present in Britain for over a year without doing substantial damage
As mentioned already the higher the temperature the shorter the incubation period will be in a midge. This varies from four to 20 days. Once a host, eg sheep or cattle, is infected viremia or infection establishes within two to four days with that host then capable of passing on the infection to a healthy midge.
The experience of the virus in Britain could possibly be giving a false sense of security with some breeders citing that the virus has been present in Britain for over a year without doing substantial damage.
This is also influencing the rate of uptake of vaccination options which have been low to date. Hopefully this will not materialise but there is nothing to predict if this will remain the case or if there will be a significant spike in cases in summer. The same can be said of cases in Wales, Northern Ireland and now Wexford with the likelihood that further cases will be identified through surveillance testing.
Notifiable disease and culling policy
Bluetongue virus is a notifiable disease, meaning that a farmer is obliged to report its presence to the Department of Agriculture.
This can be completed by phoning your regional veterinary office or out-of-hours contacting the National Disease Emergency Hotline on 01-4928026.
One of the most common questions asked in the last week is what will happen in the case of the virus being suspected and if animals will be culled. The first step is a veterinary investigation with the suspect animals and herd/flock cohorts sampled. The individual herd/flock will also be restricted. There is no definitive decision on the culling of animals.
The Department advised vets this week that culling decisions will depend on epidemiological circumstances, which includes the prevalence, distribution and health of animals, the time of year and local spread of disease.
The current position is that culling is unlikely as temperatures are too low for the spread of infection but this approach will remain under constant review.
In brief
The main symptoms of disease in sheep are oedema of the head, poor or no appetite, lethargy, lesions on the mouth, nose and coronary band and discharge from the nose, salivating from the mouth.Abortion can also occur while the birth of mummified or malformed foetuses is rare in sheep but possible.Farmers should remain vigilant for any signs of disease and report any suspect cases immediately. It is impossible to predict the likelihood of the disease spreading and prevalence levels. 
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