Comments on Classical and Atypical Scrapie in Domestic Sheep and Goats

Abstract

Scrapie is a neurodegenerative disease in domestic sheep and goats. Scrapie has a long incubation period that can vary from two to five years. The etiology is an extremely stable isoform (PrP8c) of the normal cellular prion protein (PrPc). The accumulation of this protein in the brain is thought to result in the spongiform encephalopathy that characterizes the disease. Scrapie has been reported in the United Kingdom, Ireland, most European countries, Canada, the United States, India and Japan, but not in Australia and New Zealand. Clinical signs are mostly neurological and diagnosis is usually made with immunohistochemical staining of the brainstem and retropharyngeal lymph nodes. Genetics plays a significant role in the susceptibility and incubation period of the disease and is used in control strategies. The primary method of prevention is maintenance of a closed ewe flock, purchase of sheep from uninfected farms enrolled in an approved flock certification program, or purchase of genetically resistant stock. Following diagnosis of scrapie in a flock, depopulation of genetically susceptible sheep is the only effective control measure at this time. If a sheep or goat flock is diagnosed with atypical scrapie the herd is depopulated.