They are related. Cjd and mad cow are prion disorders. Prion diseases are caused by misfolding of the prion protein. The misfolded protein is capable of inducing the normal form of the prion protein to misfold as well. In typical cjd the misfolded protein is human prion protein. In mad cow disease misfolded protein is bovine prion, which causes disease in cattle and can cause misfolding of human prion protein too.
Cows vs human. Mad cow disease/variant cjd is acquired by eating meat from from affected cows, not a risk in usa. Classical cjd may be acquired from an infected person through blood, or tissue, or, mostly it occurs sporadically due to genetic predisposition. You may consult this site: http://www. Cdc. Gov/ncidod/dvrd/cjd/index. Htm.