TSEs: Dealing with Uncertainty

摘要

Transmissible spongiform encephalopathies (TSEs) returned to the front burner with the announcement on May 20, 2003, by Canadian authorities of a case of bovine spongiform encephal-opathy (BSE)―or mad cow disease―in a cow in Alberta. The U.S. Dept. of Agriculture responded by banning any imports from Canada of products from any ruminant. With the U.S. ban still in place in early July, journalists reported that Canadian officials had begun to question the viability of the highly integrated market that had previously encouraged the flow of cattle and beef between the two countries. BSE has been shaking and reshaping markets since researchers first identified the disease in cattle in the United Kingdom in 1986. The disease was transmissible, slow to develop, and fatal. By 1989, researchers had come to believe the cause to be a prion protein that spread through cattle feed derived from rendered livestock. To stop the spread of BSE, governments in the UK and around the world imposed bans on the feeding of ruminant-derived feed to ruminants. Such feed bans have proved effective in cutting the rate of new infections and in slowing the spread of the disease into other regions.