What Is the History of Where Mad Cow Disease Came From?
In December 2003, the first case of BSE in the United States was detected in a dairy cow in the state of Washington. Two further cases were reported in 2005 and 2006. Before that, a devastating major outbreak occurred in the United Kingdom (England and Ireland) in the 1980s, peaking in 1993. Because the suspected cause was a prion transmitted in meat and bone meal products fed to cattle there, the government banned the practice of feeding such products that may contain diseased tissue to animals in 1988. By then, however, infected cattle had already entered the human food supply. At the peak of this outbreak in 1993, almost 1,000 cases per week of infected cattle were reported; the numbers have dropped dramatically since then, and currently, there are only about 10 infected cattle identified each year in the U.K. The BSE-related condition vCJD was first described in the U.K. in 1996. By 1996, several people in the U.K. and others who had lived there were identified with a variant form of CJD (vCJD), and the cause was linked to eating meat from cattle infected with mad cow disease. In June 2014, over 4,000 pounds of beef were recalled by the U.S. Department of Agriculture due to improper processing that allowed cattle brain material (dorsal root ganglia) to be mixed with processed beef.
BSE and resulting cases of vCJD in humans have been diagnosed in other European countries such as Bosnia-Herzegovina, Liechtenstein, Macedonia, Norway, Sweden, and Yugoslavia. According to the World Health Organization (WHO), over 220 cases of vCJD have been reported worldwide, with the majority occurring in the UK (177 cases) and in France (27 cases). Only four cases have been reported in the U.S., and in all four of these cases, there is evidence that indicates that the infection was acquired while abroad in Europe or the Middle East.
Because there is no way to detect BSE in blood, people who have lived for long periods in areas where mad cow disease has been found are not allowed to donate blood in the U.S.
Prion diseases are also known as transmissible spongiform encephalopathies (TSEs). Overall, prion diseases are a large group of related conditions affecting the nervous system, which affect both animals and humans. Included are Creutzfeldt-Jakob disease (CJD) and variant CJD discussed in detail herein in relation to bovine spongiform encephalopathy (BSE, mad cow disease). Another human prion disease is Gerstmann-Sträussler-Scheinker (GSS) disease (see causes below). In animals, chronic wasting disease (CWD) is found in mule deer and elk in the U.S., and scrapie is a similar condition found in sheep. Cases have been reported in the U.S. These diseases all take a long time to develop but are typically rapidly progressive once symptoms begin.
All prion diseases are fatal. Animals and humans who develop a prion disease will die of it. There is no effective treatment. It is important to understand how these diseases are transmitted in order to prevent their spread.