Scrapie is a fatal, degenerative disease affecting the central nervous system of sheep and goats. It is among a number of diseases classified as transmissible spongiform encephalopathies (TSE). Infected flocks can experience significant production losses.
Scrapie is the oldest known TSE, and under natural conditions only sheep and goats are known to be affected by scrapie. Once infected, the animal remains infected for life. Transmission of the classical scrapie agent is not completely understood, and apparently healthy sheep infected with the agent can transmit disease. Sheep and goats are typically infected as young lambs or kids, though adult sheep and goats can become infected.
Clinical signs of classical scrapie typically appear between 2 to 5 years after infection; therefore, infected animals rarely show clinical signs of infection before the age of 2 years, with the average age of clinical onset being 3-4 years. The prolonged incubation period, the subclinical nature of the infection during its early stages, and the fact that the only diagnostic tests currently available require brain or lymphoid tissue make detection of scrapie difficult. Sheep typically live 1 to 6 months after the onset of clinical signs, but some will die earlier or later. Duration of clinical signs may depend on the observational abilities of the producer. Some sheep may simply be found dead.
Due to damage to the nervous system, affected animals often show behavior changes, such as nervousness or aggression, intense rubbing, and locomotor incoordination that progresses to recumbency and death. Other clinical signs may include tremors (especially of head and neck), head pressing or “star gazing,” significant weight loss with no decrease in appetite, wool pulling, and hyperesthesia. Additional signs in affected goats may include difficulty milking, premature kidding, and pica. See videos below.
Over a period of several years the number of infected animals increases while the age at onset of clinical signs decreases, making these flocks economically unviable. Animals sold from infected flocks spread scrapie to other flocks.
Once an infected animal is detected, eradication of the disease from the flock or herd may consist of either selective depopulation of certain higher-risk exposed animals (e.g., only those that are genetically susceptible, heavily exposed, test positive or inconclusive, and/or showing clinical signs) or, less commonly, complete flock depopulation, as well as cleaning and disinfection of the premises. In a typical infected sheep flock 20 to 40 percent of the sheep are genetically susceptible. Owners of infected flocks are encouraged to restock with rams that are resistant (RR) and ewes of resistant or less susceptible genotypes (RR or QR). Researchers are still investigating the possibility of genetic resistance in goats, but have not yet identified a resistant genotype. Therefore, currently all goats are considered genetically susceptible.
See Scrapie Factsheet for more detail.
Remember: Educate, Report and Submit
The Clinical Signs of Scrapie
Total Runtime 7:41 Windows Media Player
|Hopping Gait Video
Total Runtime 14 Seconds
Windows Media Player
|Video of Infected Sheep
Total Runtime 9 Minutes Windows Media Player
|Gait Problems Video
Total Runtime 15 Seconds
Difficulty Eating Video
Total Runtime 14 Seconds
Nibbling Video Total Runtime 42 Seconds