Imagine you are a hunter in the deep woods of Pennsylvania. It’s autumn. Early morning, the sun has just crested on the horizon. The fog from the night before still coils through the leafy greens. The air hangs thick and silent; nothing moves as you slowly take in your surroundings and breathe deeply. A branch snaps to your right. Your eyes flick over and you see a flash of antler dip down as the buck nibbles on some grass. You slowly, silently, carefully raise the butt of your rifle to your shoulder. You flick the safety off and look down the scope, lining the lungs of the 8-point buck in your sights. You breathe in and squeeze the trigger. The crack of the bullet leaving shatters the silence for the first time of the day. The deer falls to the ground, struggling slightly until it lays still. You slowly lower the rifle and flick the safety back on. The deer was approximately 275 pounds and that meat will feed your family for weeks. You load up the carcass on your car and drive home, whistling a hearty tune. At home, you clean and prepare the buck. That night, you make deer burgers for your family and you all feast on the kill. A couple months after this, you find yourself in the hospital being treated for behavioral changes, confusion, memory loss, and other neurological issues. You think back to that one day in autumn, that deer had been acting a little funny hadn’t it? Maybe it had Chronic Wasting Disease? You can’t be positive, all you know from your doctors is that some sort of prion is wreaking havoc on your neurologic system.
Transmissible spongiform encephalopathies (TSEs) are neurological diseases caused by prions, which are malformed proteins. The most commonly known TSEs are mad cow disease (bovine spongiform encephalopathy) in bovine, Creutzfeldt-Jakob Disease (CJD) in humans and Chronic Wasting Disease (CWD) in deer and elk. All of these are characterized by the formation of tiny holes in the brain that can be seen under a microscope. These also cause many behavioral abnormalities in the patients infected. Mad cow disease can transfer into humans and cause variant CJD through the consumption of bovine meat contaminated with nervous system tissue. This route of transmission has made some people afraid that the prions responsible for Chronic Wasting Disease in deer and elk could move into humans through similar means.
The CDC took two routes to determine if this was the case or not. The first method they used was to look into investigations of self-reported cases of individuals who had TSEs which exhibited strange symptoms or occurred earlier than was expected. In many of these cases, the individuals were found to live in areas where the levels of CWD in the deer populations is very low or that the individuals had not consumed deer which was hunted or harvested in areas where CWD levels were high. The CDC found no correlation between the consumption of venison possibly tainted with CWD tissue and the patients exhibiting unusual symptoms of TSEs. The second method was to review investigations which tested the possibility of the prions associated with CWD entering into human cells and initiating the production of human prions (the same method that bovine spongiform encephalopathy uses). These studies found that the rate of this occurring with CWD-associated prions was of a similar level as mad cow disease-associated prions. Despite these findings, there have been no cases of TSEs in humans that have a strong linkage between the TSE developing and exposure of the individual to CWD.