CWD has not always been around. It most likely originated in the deer pens at Colorado State University where deer were kept for research purposes. The pens were built on an old sheep experimental area. It is possible that the prions that cause CWD were somehow derived from the prions that cause scrapies in sheep. Scrapies is one of several transmissible spongiform encephalopathies that produce effects similar to CWD. The prions had probably been in the soil for a long time. Unfortunately, the disease was a long time being recognized and it was an even longer time before the causal agent was identified. This explanation has not (and perhaps cannot) be confirmed, but it seems to me to be the most likely explanation for the origin of the disease.
CWD probably spread into wild populations through contact between captive deer and wild deer, either at the deer pens or by the escape and/or release of some of captive animals into the wild. It was transmitted to the west slope of Colorado in captive elk that were transported to a research facility near Maybell. Some of these elk were released into the wild when they were no longer needed. Unfortunately, the genie is out of the bottle. CWD will probably never be completely controlled, but there are management strategies that can minimize the chances for infection in wild deer, elk and moose.
