Origins of Prion Diseases – TSEs

00:01 Let's end up with a little consideration of where these prion diseases came from. In this slide illustrates a number of prion diseases of humans in different animals and tries to assemble some kind of a sequence. The panels that you see in blue are naturally incurring affections and the ones in red are transmitted. Let's start at the very top, where we have sheep, who develop spontaneously scrapie and pass it on to one another, so that was probably originally the first TSE to develop, we think it could have been passed on to deer, so if you go to the left of the sheep we have some deer with chronic wasting disease, that could also have been a spontaneous infection or it could've been passed on from sheep, because deer and sheep can often cohabitate the same pastureland. There is a transmissible encephalopathy of mink, if you go down one panel in red you see a mink there, possibly the mink ate some sheep or maybe even a deer and acquired it so it may not be a natural infection of mink.

01:07 Below the sheep we have cows who we know started to develop a BSE by feeding them, an epidemic occurred, but it may have occurred before that, possibly by being fed awful from sheep.

01:20 The cows could then pass it on to other cows by feeding cows to zoo animals and also capture of cows in the wild by other wild animals, we could've passed it on to the greater cats shown to the right of cows and your cat, your domestic cat, we know there's a TSE that affects domestic felines, acquired by eating food from cows that is contaminated with TSEs.

01:46 Below the cow is a human, who probably, who we know acquired TSE from cows and those humans can transmit those TSE to other individuals by iatrogenic and transplantation processes, but human TSEs may have in fact originated independently and spontaneously, as shown at the lower left, that blue panel, years ago, possibly the first TSEs of humans were spontaneous and then they entered the human chain, via iatrogenic or transplantation procedures.

02:19 So there may have been very few original TSE diseases that began as spontaneous TSEs, which were then passed on by infectious and consumption roots.