Changes

==Signalment==  

==Signalment==  

[[File:Sheep-scrapie1.jpg]]Scrapie affects the majority of sheep between 3 and 5 years of age and has a long incubation period of two to five years.  It is extremely durable and is able to withstand high temepratures and concentrations of formaldehyde.  Unlike BSE, scrapie is influenced by breed and genetic variation of the PrP gene within sheep populations, which can affect the infectivity and incubation period of the scrapie.  The disease has been shown to be effectively transmitted during lambing <ref name="Dickinson et al., 1974"> Dickinson AG, Stamp JT, Renwick CC, 1974. Maternal and lateral transmission of scrapie in sheep. Journal of Comparative Pathology, 84(1):19-25.</ref>, <ref name="Hourrigan et al., 1979">Hourrigan JL, Klingsporn AI, Clark WW, DeCamp M, 1979. Epidemiology of scrapie in the US. In: Prusiner SB, Hadlow W, eds. Slow transmissible diseases of the nervous system. New York: Academic Press, 331-356.</ref>, and experimental studies have shown that the ingestion of infected placenta can spread the disease in sheep and goats <ref name="Pattison et al., 1972">Pattison IH, Hoare MN, Jebbett JN, 1972. Spread of scrapie to sheep and goats by oral dosing with foetal membranes from scrapie-affected sheep. Veterinary Record, 90(17):465-468.</ref>.

Scrapie affects the majority of sheep between 3 and 5 years of age and has a long incubation period of two to five years.  It is extremely durable and is able to withstand high temepratures and concentrations of formaldehyde.  Unlike BSE, scrapie is influenced by breed and genetic variation of the PrP gene within sheep populations, which can affect the infectivity and incubation period of the scrapie.  The disease has been shown to be effectively transmitted during lambing <ref name="Dickinson et al., 1974"> Dickinson AG, Stamp JT, Renwick CC, 1974. Maternal and lateral transmission of scrapie in sheep. Journal of Comparative Pathology, 84(1):19-25.</ref>, <ref name="Hourrigan et al., 1979">Hourrigan JL, Klingsporn AI, Clark WW, DeCamp M, 1979. Epidemiology of scrapie in the US. In: Prusiner SB, Hadlow W, eds. Slow transmissible diseases of the nervous system. New York: Academic Press, 331-356.</ref>, and experimental studies have shown that the ingestion of infected placenta can spread the disease in sheep and goats <ref name="Pattison et al., 1972">Pattison IH, Hoare MN, Jebbett JN, 1972. Spread of scrapie to sheep and goats by oral dosing with foetal membranes from scrapie-affected sheep. Veterinary Record, 90(17):465-468.</ref>.

==Clinical Signs==  

==Clinical Signs==

Early clinical signs may include subtle '''behavioural and neuorological changes'''.  Sheep often have a fixed gaze, and suffer from bruxism, fine tremors, and hyperaesthesia to sound or sudden movements. Affected animals may later become exercise intolerant and develop '''progressive ataxia'''.  Sheep often find difficulty in turning, sway on their hind hindquarters and have gait abnormalities such as a high stepping gait in the forelimbs or a bunny hopping gait in the hindlimbs. Some sheep have '''intense pruritis''' that leads to compulsive rubbing, nibbling at the skin, or scraping against fixed objects.  Wool loss is typically seen over the hindquarters and lateral thorax. Lip smacking or '''nibbling reflex''' can often be elicited by scratching over the lumbar region, which is characteristic og scrapie. Significant weight loss with or without a decrease in appetite, weakness, recumbency, and death are all seen within the later stages of the disease.  

Early clinical signs may include subtle '''behavioural and neuorological changes'''.  Sheep often have a fixed gaze, and suffer from bruxism, fine tremors, and hyperaesthesia to sound or sudden movements. Affected animals may later become exercise intolerant and develop '''progressive ataxia'''.  Sheep often find difficulty in turning, sway on their hind hindquarters and have gait abnormalities such as a high stepping gait in the forelimbs or a bunny hopping gait in the hindlimbs. Some sheep have '''intense pruritis''' that leads to compulsive rubbing, nibbling at the skin, or scraping against fixed objects.  Wool loss is typically seen over the hindquarters and lateral thorax. Lip smacking or '''nibbling reflex''' can often be elicited by scratching over the lumbar region, which is characteristic og scrapie. Significant weight loss with or without a decrease in appetite, weakness, recumbency, and death are all seen within the later stages of the disease.