Scrapie, a Prion Disease of Sheep

Scrapie
Trotting disease, Nibbling disease

MP Gupta

• It is a non-febrile, fatal chronic degenerative neurologic disease of sheep and goat characterized by pruritis, long incubation period, progressive debilitation and death. • Goats are far less commonly affected than sheep.

[e-mail]

• They are generally thought to be prions, although a minority opinion suggests that TSEs may be caused by virinos or retroviruses. Prions are infectious proteins that seem to replicate by converting a normal cellular protein into copies of the prion. This cellular protein, which is called PrPc, is found on the surface of neurons. The scrapie prion, which is a pathogenic isoform of PrPc, is designated PrPSc. [e-mail] Etiology
• Scrapie is caused by infective particles- PRIONS, which is a small infectious particle capable to withstand the usual inactivation process known to destroy the virus.

[e-mail]

Etiology
• Prions contain no or little nuclear materials. The agents are not antigenic and produce no detectable immune response in the host.

[e-mail]

• As a result of scrapie surveillance, an atypical form of this disease has recently been detected in many countries in Europe, as well as in the United States. This novel form of scrapie, which was first reported from Norway in 1998, is called Nor98. [e-mail] • These particles are very resistant and can withstand boiling for 30 mins. or exposure to 20% formaline. However, 2% NaOH solution is recommended for inactivation.

[e-mail]

IP
• The incubation period is usually 2 to 5 years in sheep; cases are rare in sheep less than a year old. • Cases of scrapie have been reported in 2 to 8 year old goats. The incubation period in experimentally infected goats is less than three years, with a range of 30 to 146 weeks. [e-mail] Epidemiology
• In majority of caprine scrapie, there is a history of