An additional case of bovine spongiform encephalopathy (BSE), also known as mad cow disease, was detected in Canada in May 2009. BSE is a progressive neurological disorder in cattle caused by an abnormal prion protein. While feed regulations have been strengthened, the risk of BSE transmission remains as the new rules had only been in effect for five months as of March 2010. BSE outbreaks have occurred when infected meat-and-bone meal from sheep or cattle was fed to young calves, and there is evidence that BSE may be linked to variant Creutzfeldt-Jakob disease in humans.