Some suspect transmission may have occurred via animal feed (which would then seem likely to have infected many cattle). However, I have been concerned about CWD in wild animals (deer and elk) and potential transmission to domestic animals. CWD has been spreading in the western US and I would not be surprised by a spread to Washington State.
In either case however, it is fairly easy to imagine many cattle being infected some time ago. At the USDA news conference, they cited tests on something like 26,000 head of cattle, which they think is good and I think is a drop in the bucket. They caught this one because the Holstein was "non-ambulatory", but I find it amazing that such an animal was slaughtered and its muscle cuts processed.
As noted in the blood transfusion case, the donor was healthy at the time of donation and it took 6 1/2 years for the recipient to develop symptoms. Thus, the possibility that there are more mad cows seems quite large and it also seems likely that other ambulatory Holstein were slaughtered and eaten prior to this presumptive positive.
Might we have a time bomb on our hands, if not?
I was under the impression that feeding cattle products that contain beef protein was the commonly accepted cause of MCD. If this is not the case do the "experts" have any idea what the source cause is?
To become petfood? Got a cat on my monitor now... "Mmmmmm, purrrrrrr, prions!"