Major events related to mad cow disease, or bovine spongiform encephalopathy (BSE):

-- 1986: BSE first erupts in cattle in Britain.

-- 1993: Canada reports first case of a BSE-infected cow.

-- Oct. 2001: Holstein at center of mad cow scare in United States purchased by farm in Mabton, Wash., southeast of Yakima.

-- May 20, 2003: Scientists announce discovery of lone case of mad cow disease in Canada.

-- Dec. 9, 2003: Holstein sent to slaughter; tissue samples collected and sent to National Veterinary Services Laboratory in Ames, Iowa.

-- Dec. 22: Results showing samples tested preliminarily positive for the brain-wasting illness made available to USDA.

-- Dec. 23: Agriculture Secretary Ann Veneman announces first suspected appearance of mad cow disease in the United States.

Source: Agriculture Department (search