Scrapie
This is a chronic fatal disease of sheep and occasionally of goats caused by a Prion agent similar to BSE. The disease is reported from Europe, North America and in a few countries of Africa and Asia.
Clinical signs: Incubation period is of 2-5 years. Affected sheep show excitement, signs of muscular tremors of head and neck, wavering gait, vacant look and paraplegia. Sheep develop pruritus with wool loss and skin rubbed raw. They loose weight and ultimately die.
Diagnosis: The disease is diagnosed by the clinical signs, direct electron microscopy of brain material or demonstration of Prion protein by Western blot. The agent can be transmitted to mice and hamster and these species are being used as laboratory models for characterizing the agent.
Prevention and control: The disease is controlled by systematic detection of infected and in-contact animals and their disposal by slaughter and consequently building disease free "certified flocks".