Notes on the history of the prion diseases. Part I.

The astute observation by William Hadlow, an American veterinary neuropathologist of the similarity between the histopathology of kuru, an obscure disease of the primitive tribe in New Guinea, and scrapie of sheep, was the first clue to the etiology of the transmissible spongiform encephalopathies (TSE). The knowledge that scrapie was transmissible but only after an unusually long incubation period, that the causative agent was highly resistant to heat and formalin, and that it seemed to be able to replicate in the absence of nucleic acid, eventually led to the discovery of the prion by Stanley Pruisner and the still controversial protein-only hypothesis of etiology of the TSE.