Bluetongue: BTV-3 / BTV-8 – We take a closer look
Spring is here, the sun is shining, and with the warmer weather, the insect season is also beginning. This means that the issue of bluetongue disease is once again coming to the fore. This year, however, it is not just BTV-3 that is a concern. Added to this is the looming BTV-8 outbreak, which already reached some areas in southern Germany last autumn. To assess the risk of bluetongue in the new year, explore prevention options and address any questions, the Lower Saxony Chamber of Agriculture organised an information evening as part of the ‘Netzwerk Fokus Tierwohl’ (Animal Welfare Network). Dr Steinbeck, a specialist advisor from Boehringer Ingelheim Vetmedica GmbH, and Dr Katharina Brüning, a veterinary surgeon, provided a detailed overview of the topic during the evening.
What is bluetongue?
Bluetongue is caused by a virus and affects cattle, sheep, goats, New World camelids and wild ruminants. It is an orbivirus, of which 24 serotypes have already been identified. The incubation period is 2–15 days and viraemia can last for 40–80 days. This means that infected animals can act as carriers of the disease for up to 80 days.
In this case, transmission occurs via a so-called vector, the black fly. Black flies are small midges that can transmit the virus from one animal to others by feeding on blood. If an infection occurs within a herd, it does not immediately lead to the entire herd falling ill; instead, the prevalence remains at around 30% for a certain period of time.
Typical symptoms of infection include fever and a marked deterioration in general health, as well as swelling of the tongue, lips and head. Ulcers and inflammation may also occur. As a result, the animals often experience increased salivation and a significant reduction in feed intake. Furthermore, joint and hoof inflammation may occur, which in severe cases can even lead to the animals losing their hooves. A decline in milk production may also occur over a period of approximately two months. In the worst-case scenario, bluetongue leads to death. The symptoms are most pronounced in sheep, and the mortality rate is also highest in this species. In cattle, the clinical signs are generally less severe, but should not be underestimated.
Furthermore, intrauterine infection also plays a major role. Bluetongue can cause abortions, stillbirths and infertility. In addition, infection of the foetus can lead to severe developmental disorders.
Spread in Germany
The first outbreak of bluetongue in Germany occurred in 2007 and 2008. At that time, the strain involved was serotype 8 (BTV-8). However, the virus was brought under control again through compulsory vaccination, meaning that it was not until October 2023 that another outbreak occurred within Germany. Since 2023, serotype 3 (BTV-3) has been circulating in Germany. In addition, isolated cases of serotype 8 (BTV-8) were reported in southern and central Germany in October 2025. Two different strains of these are currently circulating. It is thought that the ‘new’ BTV-8 strain causes significantly more clinical symptoms than the ‘old’ strain.
Bluetongue is a notifiable disease in Germany (notification requirement in accordance with the Animal Disease Notification Ordinance (TierSeuchMeldV) of 10 March 2026). In the event of an infection, livestock owners or carers are therefore required to notify the veterinary authority.
Control of bluetongue
It is possible to reduce the risk of infection by minimising midge pressure. This can be achieved by keeping animals indoors or by ventilating the shed. As midges are primarily active at dusk and dawn, such measures are particularly recommended at these times of day. Another option is to treat the animals with insect repellents and to avoid shearing sheep. The latter, however, must take into account the animals’ need to regulate their body temperature.
If infection with the BT virus occurs, there is no direct treatment for the disease. As it is a viral disease, only the symptoms can be alleviated. For this reason, vaccination is the only measure that can protect the animals from a severe course of the disease. Even vaccinated animals can fall ill. However, they tend to experience milder symptoms and a significantly lower mortality rate.
There is currently no compulsory vaccination, meaning vaccination is voluntary. However, the Standing Committee on Vaccination in Veterinary Medicine (Stiko Vet) recommends vaccinating at-risk ruminants.
Depending on the target species and the vaccine, one or two doses are required for primary immunisation. A booster dose is recommended in accordance with the package leaflet and can also be documented as such in the Hi-Tier database. To reduce the spread of the pathogen, the entire herd should be vaccinated. As vaccination also places a strain on the body and the immune system, it is advised to vaccinate only healthy animals. Vaccination is also recommended for herds that are directly at risk of disease outbreaks or that already have cases of the disease within the herd.
It is important to note that there is no cross-immunity between serotypes 3 and 8. In this case, vaccination against BTV-3 does not provide protection against a BTV-8 infection. To provide protection against both serotypes, vaccination with two different vaccines is necessary. Unfortunately, there is currently no combined vaccine available that covers both serotypes in a single vaccination.
To control a disease, a stable vaccination coverage of > 80% of susceptible animals is required. This figure is currently nowhere near being achieved in Lower Saxony. According to the latest figures from 13 April 2026, vaccination coverage in Lower Saxony for BTV-3 stands at 39% for cattle, 69 per cent in sheep and 30 per cent in goats, whilst for BTV-8, vaccination coverage in Lower Saxony for all three species ranges between 3.1 per cent and 3.3 per cent.
The authorised vaccines are considered to be very well tolerated. Studies on fertility have also failed to establish any link between vaccination and fertility problems.
Depending on the federal state, animal disease funds offer support for vaccination against bluetongue. Please contact the animal disease fund in your federal state for further information.
Further information on bluetongue
Information on bluetongue (Lower Saxony Ministry of Food, Agriculture and Consumer Protection)
Risk assessment by the Friedrich Löffler Institute
Animal disease incidents – Friedrich Löffler Institute
Animal disease information from LAVES
Bluetongue: Danger on the horizon – how to protect your animals effectively
Author: Lea Fee Ammermann, Lower Saxony Chamber of Agriculture