Unfortunately, the "Alzheimer's is different and couldn't be PrP related" Argument doesn't quite have legs. Due in part to the fact that, statistically, Alzheimer's prevalence is growing at a rate that far outstrips the growth of our senescent population. The most damning evidence is, ironically, evidence that it's likely that a large chunk of "Alzheimer's" isn't Alzheimer's.
An intensive autopsy study by Laura Manuelidis (Head of Neuropathology at Yale, if that counts for anything other than an appeal to authority) turned up about 13% of brains diagnosed as Alzheimer's as having distinct CJD pathology.
Back of the envelope math - ~500,000 new "Alzheimer's" cases this year X 13% showing TSE pathology = 65,000
So, assuming the researchers at Yale aren't telling tall tales, the research points toward human TSE prevalence in the US at about 185X higher than the oft quoted 1 in a million figure.
Couple that with the Czub research showing transmission to macaques through infected venison muscle meat (read the actual release by Czub and not the con job about monkey cannibalism a certain farmed deer advocate put out to every outlet that would print it), plus the study by Kristen Davenport at CSU showing in vitro conversion of human prion proteins by CWD PrP and you have about all the correlative experimental evidence you're likely to get.
Oh, and I nearly forgot the documented increase in CJD diagnoses in Wisconsin in lagging proportion to the growth in CWD prevalence being written off to better surveillance.
Does anyone here remember John Gummer going on television and having his daughter eat a hamburger to show that BSE was of no oncern to humans. That was six years before the first confirmed vCJD case.
If you're waiting for the human studies showing definitive causation, that study is you and everyone willingly and unwillingly exposed to it. It ain't legal to run experiments like that on humans in a laboratory setting. Probably for reasons with which most here would agree.
Seems pronghorns and bear are getting more exciting and delicious by the day...