new case of mad cow disease in canada

ny times reports today that canada has found a new case of mad cow disease:

The sick cow was born in March 1998, months after the United States and Canada instituted bans on feed that contained protein made from livestock and other ruminants.

Mad cow disease is thought to be caused by misfolded proteins known as prions, which cause other proteins to misfold, leading to brain damage and other problems. It is believed to spread through once common feeding practices, like making feed from certain animal byproducts and conserving the milk of dairy cattle for sale by feeding their calves cattle blood.

Officials at the Canadian Food Inspection Agency said they believed that the cow was probably infected by eating food produced before the ban.