Written by Emilie, veterinarian
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In October 2023, Belgium lost its status as a bluetongue-free country following the detection of bluetongue virus serotype 3 (BTV-3) at a sheep farm. During the summer of 2024, this serotype spread at an alarming rate across Europe, with outbreaks reported in the Netherlands, Belgium, France, Germany, Luxembourg, Denmark, Switzerland, the Czech Republic, and Great Britain. These outbreaks caused significant economic damage to the livestock sector and placed immense pressure on sheep and cattle farmers in the affected regions.
At the start of 2025, the threat of a resurgence of the BTV-3 bluetongue epidemic remains high. Additionally, the risk of the arrival of bluetongue virus serotype 8 (BTV-8) is increasing, as is the threat of Epizootic Hemorrhagic Disease (EHD), a related disease that causes similar symptoms. Since October 2022, EHD has been spreading rapidly in several European countries, including France. Although Belgium is currently still free of EHD, vigilance remains crucial to protect livestock from this rapidly emerging threat.
Given the severity of the situation, Belgium has announced preventive measures for 2025. One of the key steps is the implementation of mandatory vaccination campaigns to prevent the spread of these diseases and mitigate their impact on the livestock sector.
In January 2025, the mandatory vaccination campaign against BT and EHD for cattle and sheep will begin in Belgium.
Animals are considered fully vaccinated if they have received all primary vaccinations before the 1st of June 2025, and if these vaccinations are registered in Sanitel.
Since the 15th of January 2025, compulsory notification of bluetongue and epizootic haemorrhagic disease has returned for animal species susceptible to the diseases.
This means that livestock farmers must contact a veterinary surgeon if they suspect bluetongue or EHD in one of their animals.
If the vet also suspects bluetongue or EHD, he/she will collect blood for further diagnostics.
A PCR test should be used to analyse these samples to confirm or exclude the presence of the virus. In Flanders, blood samples must be sent to DGZ (Diergezondheidszorg Vlaanderen), which is responsible for performing the analysis and further follow-up.
Bluetongue is a viral disease that mainly affects sheep and cattle, but other domestic and wild ruminants can also become infected. The disease is not transmitted from animal to animal and does not pose a risk to human health. However, bluetongue can cause significant damage to livestock farms. The bluetongue virus is spread exclusively by the bite of infected midges of the Culicoides species, small blood-sucking mosquitoes that act as vectors. Although sheep and cattle are the main victims, other animal species can also become accidentally infected with bluetongue virus. This was demonstrated during the outbreak in the Netherlands in 2023, when two dogs tested positive for the virus in addition to ruminants.
Epizootic Hemorrhagic Disease (EHD) is a severe viral infection that closely resembles bluetongue. Like bluetongue, the EHD virus is not transmitted directly from animal to animal but spreads through biting midges. The disease primarily affects cattle and (wild) deer species, with symptoms that can be severe and sometimes even fatal.
Other ruminants, such as goats and sheep, generally show little to no symptoms and appear to be less susceptible to the virus. However, this does not make the disease any less concerning, as EHD can cause significant economic damage in livestock farming and can pose a threat to the health of wild populations.
Bluetongue viruses originally occurred only in regions where their vectors, the biting midges, could thrive due to favourable climatic conditions. These conditions, such as tropical and subtropical climates, are characterized by high temperatures and sufficient humidity throughout the year.
However, in 1998, the distribution pattern of bluetongue changed dramatically. The virus spread across the entire Mediterranean region and then moved further north, reaching Northwest Europe and even Scandinavia. Initially, climate change was thought to be responsible for this expansion, as higher temperatures allowed tropical midge species to migrate to more northern areas. However, later research revealed that the bluetongue virus had adapted by using different vector species. This finding increases concerns that the virus can successfully overwinter in temperate regions, such as northwest Europe.
In November 2022, an outbreak of epizootic haemorrhagic disease (EHD) was confirmed in cattle on several farms on the Italian islands of Sardinia and Sicily. This was the first outbreak in Europe.
Like the bluetongue virus, the EHD virus originally occurred mainly in warmer regions, such as North Africa, Australia, and Asia. EHD transmission occurs exclusively through biting midges (Culicoides species), the same vectors responsible for the spread of bluetongue.
Adult midges are most active from sunset to sunrise, with peak activity between April and October. However, in mild temperatures and sufficient humidity, this active period can be extended. Midges thrive best in humid environments with organic material, such as puddles, ponds, and slow-moving water—ideal conditions for their reproduction.
At temperatures below 10°C, midges become less active, but infected eggs or larvae can survive the winter. In spring, these develop into adult, infected midges that can infect new animals.
Please note: Both bluetongue and EHD can be transmitted not only through active vectors, such as midges, but also through passive vectors, such as reused injection needles, which is a common practice in livestock farming. This underlines the need for strict hygiene protocols and the use of separate needles when vaccinating or treating animals.
Bluetongue is a viral disease affecting ruminants such as sheep, goats and cattle. However, sheep are the most susceptible to this disease. Below is a summary of the main symptoms for each species:
Symptoms in sheep:
In sheep, the disease is often severe. Without treatment, they usually die within 8 to 10 days. Som animals survive and recover slowly.
Symptoms in cattle and goats:
Differential diagnosis: If bluetongue is suspected, other conditions should be ruled out: such as EHD, ovine catarrhal fever (BCK), foot-and-mouth disease, photosensitisation, bovine viral diarrhoea (BVD) and Ecthyma.
Bluetongue requires a prompt and accurate diagnosis in order to limit the impact on the animal and the herd. In case of suspicious symptoms, always consult a veterinarian immediately.
Epizootic haemorrhagic disease (EHD) mainly affects cattle and wild deer. Goats and sheep show little or no symptoms.
The EHD virus damages the inner walls of small blood vessels, which can lead to fluid accumulation, bleeding and ulcers. Symptoms are very similar to those of bluetongue:
Cattle may experience additional problems such as reproductive problems and reduced milk production. However, mortality in cattle is rare (<1%).
In cervids, the disease can be severe. Morbidity and mortality can reach 90%, with mortality rates of 25-50% in peracute and acute cases. Sheep and goats usually show no clinical signs.
Differential diagnosis in cattle: The differential diagnosis for EHD should include: Bluetongue, foot-and-mouth disease, Bovine catarrhal fever (BCK), sunburn, Bovine viral diarrhoeal-mucosal disease (BVD-MD), Infectious rhinotracheitis (IBR), Bovine respiratory disease (BRD).
There is no specific treatment for bluetongue and EHD. Caring for affected animals focuses mainly on symptomatic treatment aimed at optimising welfare and comfort.
Possible treatment options:
Prevention is always better than cure, at least when it comes to bluetongue and EHD.
Herbavita offers a range of special supplements to support the immune system in ruminants, such as
Administering these supplements at strategic times, such as during vaccinations or other stressful conditions, can significantly improve animals’ resilience. Not only does this make them more resilient to external challenges, but it also contributes to the overall effectiveness of vaccinations and other preventive health measures.
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