While the association between mad cow disease and CJD is tentative, there have been several well documented cases in which patients become infected as a result of surgical implantations involving either contaminated tissues or instruments. Cases c aused by the injection of growth hormone extracted from raw tissues have also been documented. The cerebellum has many functions, such as controlling gait and coordination. GSSD patients have difficulties maintaining balance. Fatal familial insomnia first manifests as difficulty sleeping, bu t patients soon develop dementia and ultimately die.
Many mammals get prion diseases, including mink, squirrels, elk, deer, and cats.
The best known example is scrapie in sheep. Affected sheep lose coordination and become irritable. In the 1970s, British farmers used ground offal from dead sheep to feed cattle -after which the cattle began to exhibit symptoms similar to those of the affected sheep. In 1988, the British government banned the practice of feeding cattle with infected sheep. However, an unknown number of people had a lready eaten potentially contaminated beef.