Abstract
Animal prion diseases are a group of neurodegenerative, transmissible and fatal disorders that affect several animal species. The causative agent called prion, is a misfolded isoform of normal cellular prion protein, which is found constitutively in cells with higher concentration in the central nervous system. In this review, we explored the sources of infection and different natural transmission routes of animal prion diseases in susceptible populations. Chronic wasting disease in cervids and scrapie in small ruminants are prion diseases capable of maintain themselves in susceptible populations through horizontal and vertical transmission. The other prion animal diseases can only be transmitted through food contaminated with prions. Bovine spongiform encephalopathy is the only animal prion disease considered zoonotic, however, due to its inability to transmit within a population, it could be controlled. The emergence of atypical cases of scrapie and bovine spongiform encephalopathy, even the recent report of prion disease in camels, demonstrates the importance to understand the transmission routes of prion diseases in order to take measures to control them and to assess the risks to human and animal health.

Key words: Animal prion diseases; Scrapie; Bovine spongiform encephalopathy; Chronic wasting disease; Transmissible spongiform encephalopathies