I recently got interested in the disease that's plaguing disease called "chronic wasting disease". The story that circulates the media about the disease it occurs in wild deer populations and is "spreading" around the USA.
However, after just a little research, the story I find is CWD originated in captive deer populations. It specifically started in Colorado back in 1967, then kept cropping up in various farmed deer and elk populations ever since.
Researchers published "Alterations in gut microbiota linked to provenance, sex, and chronic wasting disease in white-tailed deer (Odocoileus virginianus)" (link to article) in 2021. It's pretty interesting. Their theory is the feed and high population density on deer farms--yes they farm deer--creates the conditions for CWD.
Anyway, I'm going to keep reading up on it.