Todayโs path rounds are on ๐ฌ๐๐ซ๐๐ฉ๐ข๐!
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐๐๐ซ๐๐ฉ๐ข๐ was the first ๐ฉ๐ซ๐ข๐จ๐ง disease reported, and was first described in the UK in 1732. Since then, it has been described worldwide!
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
Sheep get this disease!
๐๐ก๐๐ญ ๐๐๐ฎ๐ฌ๐๐ฌ ๐ข๐ญ?
Not much is known about how prion diseases work, but the basic concept is that prions, a brain protein, get folded incorrectly for some reason. A misfolded prion can cause misfolding of normal prions, causing a self-perpetuating cycle where eventually the majority of prions are abnormal. These abnormal prions are thought to disrupt the cell membrane of neurons, causing disease. The exact trigger for this cascade of prion misfolding in scrapie is unknown, but is thought to be from ๐ข๐ง๐ ๐๐ฌ๐ญ๐ข๐จ๐ง of a misfolded prion.
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
Disrupting the cell membranes of neurons leads to ๐ง๐๐ฎ๐ซ๐จ๐ฅ๐จ๐ ๐ข๐ ๐ฌ๐ข๐ ๐ง๐ฌ, which usually present as trembling, seizures and excitability in these sheep. The classic finding of scrapie is ๐ฌ๐๐ฏ๐๐ซ๐ ๐ข๐ญ๐๐ก๐ข๐ง๐ and ๐ฌ๐๐ฅ๐-๐ญ๐ซ๐๐ฎ๐ฆ๐, leading to loss of wool and abrasions on the skin. Eventually, the neurologic signs become so severe that the animal becomes paralyzed, unable to eat and ultimately dies.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
Diagnosis typically involves looking at a section of brain under the microscope, to look for characteristic โholeyโ neurons. While this change isnโt ๐ฉ๐๐ญ๐ก๐จ๐ ๐ง๐จ๐ฆ๐จ๐ง๐ข๐ (only thing it could be) for scrapie, it is a very good clue! In the live animal, a biopsy of the tonsil can be taken for direct identification of misfolded prions.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐? ๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ฉ๐ซ๐๐ฏ๐๐ง๐ญ๐๐?
Unfortunately there is no treatment for scrapie, making prevention key. Because of the severity of the disease, many countries require contact tracing, quarantine and testing of affected sheep. Interestingly, susceptibility to scrapie is ๐ ๐๐ง๐๐ญ๐ข๐๐๐ฅ๐ฅ๐ฒ ๐ฅ๐ข๐ง๐ค๐๐ in sheep, so there are current efforts to breed scrapie-resistant sheep around the world.
๐๐ก๐จ๐ญ๐จ๐ฌ
1-3) Sheep with hair loss and wounds from itching.
4-5) Vacuolated neurons in the brain.
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Maxie, G. Jubb, Kennedy and Palmerโs Pathology of Domestic Animals, Volume 1. Sixth Edition.
Bulgin MS. Overview of Scrapie. Merck Veterinary Manual 2016.
Photos 1-5 ยฉ Noahโs Arkive contributors King, Ward, Acland licensed under CC BY-SA 4.0.
