Researchers at the University of Texas Medical Branch in Galveston have observed infectious prions from hamsters causing abnormal protein development in mice, along with a range of other observations on prion actions in test tube environments. From the article: "...they also found that when a prion jumps species, it produces a new kind of prion. 'This is very worrisome,' says Claudio Soto, who led the research, published in Cell. 'The universe of possible prions could be much larger than we thought.'"
Sounds like another good reason to donate your spare CPU cycles to projects like Folding@home."