There are actually 7 diseases which are classified as sponigiform
encephalopathies.  Scrapie in sheep and goats, bovine spongiform
encephalopathy (BSE or "Mad Cow Disease") in cattle, transmissible mink
encephalopathy (TME), chronic wasting disease (CWD) in elk and deer,
kuru, familial insomnia, and Creutzfeldt-Jakob disease (CJD) in humans.
 
Scrapie, TME, CWD, and CJD have all been reported here in the US.  Plus TME
has been shown to be infectious to ferrets in an experimentally setting.
Most of the pet foods use chicken and/or fish as the protein source, so mad
cow disease should not be a problem.  Plus mad cow disease has not been
reported here in the US.
 
Hope that clears things up,
Jerry Murray, DVM
[Posted in FML issue 3411]