Canadian authorities have said that a beef cow in Alberta was confirmed to have mad cow disease. The Canadian Food Inspection Agency (CFIA) stated the cow was killed, but that no part of it reached the human food or animal feed systems.
This is the first case of mad cow disease in cattle in Canada since 2011.
Mad cow disease is officially called bovine spongiform encephalitis (BSE). It is a fatal neurological disease that causes the brain to develop a spongy consistency. Cattle infected with it have behavioral changes and start to stagger. The infectious agent is a misfolded protein called a prion that causes other proteins to misfold, which spreads the disease. Prions are not destroyed by cooking. The disease has a long incubation period, up to 8 years in cattle.
The CFIA says that it is working to determine how the cow became infected. BSE was found to be spread by feeding cattle, which are normally vegetarians, feed that was supplemented with meat and bones from infected animals. Canada banned the practice of using this type of feed in 1997.
BSE can be transmitted to humans by eating food contaminated with prions, which are found in greatest numbers in the brain, spinal cord, or digestive tract of infected animals. It is one of a group of diseases called transmissible spongiform encephalopathies. In humans, the same disease is called new variant Creutzfeldt-Jakob disease.
Mad cow disease was first seen in the United Kingdom in 1986 and was found to have spread to people who ate contaminated beef. As of 2014, 177 people have contracted and died from new variant Creutzfeldt-Jakob disease there. There are fewer than five new cases diagnosed per year in the United Kingdom since the country killed all suspect cattle in the late 1980s and banned the use of meat and bone in cattle feed.
Other forms of transmissible spongiform encephalopathy include scrapie in sheep and a wasting disease that is seen in deer and elk.