The transmissible spongiform encephalopathies (TSE) don´t occur in swine in natural conditions. However, the bovine spongiform encephalopathy (BSE) agent, inoculated by 3 simultaneous routes in pigs, is able to reproduce a neurological disease in these animals. On the other hand, the BSE agent after passage in sheep under experimental conditions (sheep-BSE) exhibits altered pathobiologic properties. This new agent is able to cross the cattle-pig transmission barrier more efficiently than BSE..