Scrape is a transmissible Spongiform encephalopathy in sheep and goats, which causes neurological signs in affected animals. Confirmation of disease is made post-mortem on examination of the brain, which also allows classification into different forms of scrape, classical, scrape, atypical scrape, and rarely other forms transmitted from other species such as bovine fungi form encephalopathy. Abbreviated BSE Scrape is a listed disease by the World Health Organization for Animal Health, but the disease is often not recognized and affected small ruminants.
This video demonstrates a short clinical examination protocol lasting approximately five minutes to aid in the detection of clinical cases affected by transmissible, spongy form and encephalopathies using three sheep as examples. Example one is A clinically healthy sheep cerebrally inoculated with BSC. Free bovine brain homogenate examined at 49 months post inoculation, which represents a control.
Example two is a clinically affected sheep interest cerebrally inoculated with atypical scrapy OV brain homogenate examined at 36 months post inoculation, which represents an atypical scrapy case. Example three is a clinically affected sheep interest re inoculate with atypical BSE bovine brain Homogenate examined at 50 months post inoculation, which presents clinically similar to classical scrapy. For this reason, a classical scrapy case is not included.
Assessment or posture. The healthy sheep carrying the ear tag number one and indicated by the red arrow displays a normal posture when undisturbed in the pen. The posture of the atypical scrapy sheep also appears normal.
The sheep with atypical BSC appears slightly hunched and tends to sound with its hind limbs. Wide based assessment of behavior as expected in normal sheep, the healthy sheep stays within the group and follows the movements of the examiner. With its size approaching and catching the sheep does not elicit any abnormality.
The atypical scrapy sheep behaves differently to the other sheep in the pen and stands with its rear towards the camera, whereas all other sheep look towards the camera. Sheep are social animals are moving groups, but this sheep does immediately follow other sheep and appears to be slow in realizing that the other sheep are gone clockwise. Circling is elicited after examination of this sheet.
This compulsive behavior only stops when the sheep is approached and it runs away. The sheep with atypical BSC falls on the floor when handled after being caught. Menace response testing, moving the hand or several fingers several times towards each eye of the animal without touching any facial hairs or creating any air.
Turbulence should elicit blinking as seen for both eyes and the healthy sheep. The men's response is lost in the sheep with atypical scrapy, which does not blink. Although its ability to blink when the eyelids are touched is not impaired.
The atypical BSE sheet blinks in response to the menace, but the blink response is weak in the left eye compared to the blink response. When the eyelid is touched, Testing of the scratch response, the tests are here performed whilst the sheep stands next to a wall, and this is prevented from escaping forward by one leg of the examiner, the sheep is calm enough to continue with the test. Several areas of the back are scratched here, the sacral lumbar tho columbar, mid-thoracic, and cranial thoracic regions with a pause between each scratching episode to observe the response.
This clinically healthy sheep does not show a repeatable stereotypical response. Similarly, the sheep with atypical scrapy does not respond to scratching of several areas of the back. A response, however, is elicited when the sheep with atypical BSC is scratched.
Depending on the area that is scratched, is either reacts with nibbling movements of the lip or head movements. This response is considered Positive Checking for wall loss and skin lesions. Extensive areas of wall loss with or without skin lesions can usually be observed from a distance, but closer examination of the sheep during restraint may identify smaller areas of wall loss caused by excessive pruritus.
These areas are often found on the head, back, rum and side of thorax or abdomen, often bilateral symmetrical. While no wall loss is detected in the control sheep and the sheep with atypical scrapy, the sheep with atypical BSC has lost its wool on the pole. The skin is otherwise intact except for a small scab that has formed after damage of the skin.
This may have been caused by excessive pruritus scoring body condition. The animal's body condition is scored by feeling the transverse and dorsal processes of the lumbar. This can also be done during the scratch testing of the sheep.
A score from nought to five may be used with five being assigned to a very obese sheep. This is represented in the drawn image of a cross section through the lumbar vertebral column. The processes of the vertebrae are covered by muscle in red and fat tissue in yellow, and it would be impossible to fill the ends of the transverse processes even if you applied pressure to the skin.
By contrast, the body condition is poor. If the ends of the spinal processes feel sharp, that applying any pressure and no overlaying factor sheet can be felt as demonstrated in this image. This would be scored as naught.
The body condition is very good in the clinically healthy sheep with a score of four atypical scrapie caused a loss in bodily condition, which is only fair with a score of two. Whereas the sheep with atypical BSC has maintained a good body condition score of three blindfolding. The animal, the sheep's head is covered here with a handmade blindfold, which could be any non C3 bag where one corner is cut off the animal's nose to allow breathing before releasing the sheep, make sure it is safe for the animal to do so.
Some sheep may panic and run or jump around and may be in danger of hurting themselves or others. In this case, do not release the sheep completely and study animal movements while still holding the animal. The healthy sheep remains calm and blindfolded, but tosses its head in an attempt to remove the blindfold.
Its movement or balance is not impaired. In contrast, the sheep with atypical scrapie starts circling in clockwise direction. There is also loss of balance.
The sheep with atypical BSC is reluctant to move and leans against the hurdle, but whilst doing so, it cross its four legs and loss of balance is evident. Assessment of the animal's movement, the gait in the clinically healthy sheep appears normal. There is no obvious tremor, neither when the sheep is left undisturbed nor earlier during handling.
Ataxia is present in the sheep with atypical scrapie. It slips when it follows the other sheep and its hind limb movements appear. Incoordinated a fine head tremor can be observed briefly when the sheep stands in the group.
A texture is also apparent in the sheep notated with atypical BSE. There is a loss of balance in coordination and hyper metra as can be seen by the high stepping fall. Gait interpretation.
Clinical signs shown in those sheep affected by transmissible spongy form, encephalopathies included abnormal behavior, an absent menace response, a positive scratch response alopecia, skin damage circling when blindfolded in coordination and tremor, the display of one or in the case is presented here. More of any of these signs should alert the examiner and scrape should be considered as one of the causes.Conclusion. This video shows the clinical examination protocol performed on a clinically healthy sheep and gives examples of abnormal findings in sheep affected by transmissible spongiform encephalopathies.
This protocol is useful to detect clinically suspicious cases which may be examined in more detail to rule out other diseases with a similar clinical presentation or may be used to assess clinical onset disease progression or clinical endpoints. In experimental studies of transmissible spongy form encephalopathies in small ruminants.
