Bluetongue

What is it?

Bluetongue is a viral disease that mainly affects sheep, but also cattle and goats. It is transmitted by small biting insects and causes inflammation of the mucous membranes and blood vessels. It represents an important economic issue for livestock farming in Tunisia and around the world.

Commonly observed signs

These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.

Causes and risk factors

The disease is caused by a virus called Bluetongue virus, belonging to the Reoviridae family. There are several serotypes of this virus, which complicates the immune protection of animals. The virus multiplies in the body of the infected animal and in certain insect vectors.

Areas where Culicoides midges proliferate, particularly humid and warm regions, are at increased risk. Summer periods and farms located near stagnant water points favor the presence of insect vectors. Lack of herd vaccination is also a significant risk factor.

Transmission

The virus is transmitted mainly through the bite of small midges called Culicoides, which act as biological vectors. The disease is not transmitted directly from one animal to another by simple contact. Transmission can also occur from mother to fetus in certain cases.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

Treatment

There is no treatment that eliminates the virus. Care is "symptomatic": it aims to relieve the animal and help it recover.

The veterinarian examines the animal and can confirm the disease through laboratory tests. Bluetongue is a notifiable disease and must be reported to the veterinary authorities.

The vet may prescribe anti-inflammatories and medication for fever and pain. Antibiotics may be used if a bacterial infection develops alongside the disease.

Supportive care is important: rest, shade, fresh water available at all times, and soft, easy-to-eat food. Lesions in the mouth and on the feet can be cleaned under veterinary supervision.

The veterinarian also advises isolating sick animals in a place protected from midges, as this limits the spread of the virus. Never give medication without veterinary advice.

Prevention

Vaccination

Vaccines exist against Bluetongue. They protect against one or more specific serotypes of the virus, so the vaccine must match the serotype present in the region.

Vaccination is generally given before the midge season, i.e. before the warm season. The exact schedule (age, number of injections, boosters) depends on the vaccine and on the instructions of the veterinary authorities.

The vaccine is mainly used in sheep and cattle. For wild animals or animals in zoological parks, the decision rests with the veterinarian.

Ask your veterinarian or the official veterinary services whether vaccination is recommended in your area.

Possible complications

In sheep, the disease can be serious. Mouth lesions interfere with feeding and cause significant weight loss.

Foot involvement causes lasting lameness. Wool may also fall out after the disease.

Breathing difficulties can progress to pneumonia, which is sometimes fatal. Secondary bacterial infections are possible.

In pregnant females, the virus can cause abortions or malformations in their offspring.

The disease reduces milk, meat and wool production. It can also hamper animal trade. Cattle and goats are often carriers without visible signs and can be a source of the virus for midges.

When to see a veterinarian

References

WOAH — Organisation mondiale de la santé animale (ex-OIE)

Content reviewed by the TunisieVet editorial team · Updated 05 November 2026