- 6m -5y incubation period .
- Sheep first appear hyperexcitable with an erect head and high-stepping gait.
- Sheep make lip movements when their back is scratched.
- Later on muscle tremors, bilateral intense pruritis or stupor and finally ataxia may develop with accompanying anorexia and emaciation.
- dd, ectoparasites, (Maedi-Visna, Louping ill and pregnancy toxaemia)
- Deaths are most frequent at 2-5 years of age and up to 10% of the flock may die in an endemic area.

Mink, from sheep offal with further spread by biting (mink encephalopathy)