Bluetongue is a viral disease that primarily affects ruminants, particularly sheep and cattle. It's caused by the Bluetongue virus (BTV), which belongs to the *Orbivirus* genus within the *Reoviridae* family. The disease is non-contagious and spreads mainly through bites from *Culicoides* midges, making it prevalent in warmer regions where these insects thrive.

Symptoms in Cattle and Sheep

In Sheep

Sheep are particularly susceptible to Bluetongue, and symptoms are generally more severe:

**Fever**: A high fever is one of the initial symptoms.

**Edema and Swelling**: The face, lips, and tongue may become swollen, leading to a characteristic blue tongue in severe cases (hence the name).

**Mouth Lesions**: Ulcers and erosions in the mouth can lead to drooling and difficulty eating.

**Lameness**: Due to inflammation of the hooves, sheep may exhibit lameness or reluctance to move.

**Respiratory Issues**: Difficulty breathing can occur due to edema in the throat.

**Weight Loss**: Reduced appetite and difficulty eating can lead to rapid weight loss.

#### In Cattle

Cattle can be infected but usually experience milder symptoms:

**Mild Fever**: Fever is generally less severe than in sheep.

**Oral Lesions**: Similar to sheep, but typically milder, with occasional drooling.

**Reproductive Issues**: In some cases, cows may experience decreased fertility or fetal abnormalities.

**Swelling**: Occasionally, cattle may have swelling around the head and neck, though less dramatically than in sheep.

**Reduced Milk Production**: Due to the animal's overall reduced health status.

Transmission

Bluetongue does not spread directly between animals. Instead, it relies on the *Culicoides* midges for transmission. The virus has a seasonal pattern, with outbreaks typically occurring in late summer and early fall in temperate climates.

Diagnosis and Prevention

Diagnosis is confirmed through PCR tests, virus isolation, or serological assays. Preventing Bluetongue largely involves vector control (such as using insecticides or repellents to reduce midge populations) and vaccination in endemic areas. Vaccination is typically limited to affected regions due to the complexity of the virus, which has multiple serotypes, so specific vaccines are necessary.

Economic Impact

Bluetongue can cause significant economic losses due to reduced productivity, increased mortality in sheep, trade restrictions, and veterinary costs.