“…Wilesmith et al, 1988). Contrary to that, an oral transmission of PrP Sc and an ensuing infection seems to be blocked in non-ruminants such as pigs and chicken (Matthews and Cooke, 2003), presumably by a species-specific barrier in the gut (Hill and Collinge, 2002). Although it has been shown that pigs are capable of developing a TSE crisis after multiple parenteral injections of PrP Sc contaminated brain homogenate, no transmission occurred after an oral exposure of PrP Sc , even in a 100 times higher concentration than the one determined necessary for oral infection in cattle (Wells et al, 2003).…”