Symptoms and Diagnosis

Major symptoms of Bluetongue are excessive salivation, high fever, swelling of the face and tongue as well as cyanosis (blue or purple discolouration) of the tongue. In minority of the animals, the tongues and lips will swell, giving it the tongue its typical blue appearance. Prominent nasal symptoms are nasal discharge and heavy breathing.

Foot lesions beginning with coronitis (inflammation of the coronary band) and ending up in lameness will develop in some animals. In sheep, This can lead to knee-walking. While all symptoms usually develop within a month, the incubation period is 5-20 days. Despite the normally low mortality rate of Bluetongue disease, susceptible breeds of sheep in Africa face much higher mortality rates. In Africa, local breeds of sheep may not die from the disease but the death rate in imported breeds may go as high as 90%.