I first heard about this here (Hotlinking of vid not allowed, gonna have to head over to youtube - don't worry I timestamped it).

It's a chronic wasting illness, induced by a specific protein that eats the brain of deer, elk and moose, currently passing around the US and Canada.

If it sounds familiar, that's because it's basically the same thing as BSE/"Mad Cow Disease" which causes Creutzfeldt-Jakob disease in humans.

Some states have banned sale/transit of certain animal parts - and it appears uncertain whether or not this variation can affect humans.

The disease causes them to become lazy and wither away and die - but it also inhibits their fear of humans - basically, if they come up to you, don't touch them.