Sorry, can't let this one slip.

Intracerebral injections of homogenate transcend the species barrier, because you are injecting directly into the brain metals which react with the production of new PrPC proteins, etc. 

There is no way this is going to happen without medical intervention.

Prion diseases are species specific.  Unless the rogue metals, metal complexes are iatrogenically injected (clinical intervention such as vaccinations,etc), all prion disease is spontaneous within the species.