Animal Transmissible Spongiform Encephalopathies (TSEs) and Their Impact on Animal and Human Health Worldwide
Bovine Spongiform Encephalopathy (BSE) was first diagnosed in Great Britain in 1986. Between 1986 and May 1998 there have been over 171,000 confirmed cases of BSE reported in Great Britain. In addition, BSE has been diagnosed in native cattle from other countries of the United Kingdom and Europe. The BSE epidemic in the United Kingdom peaked in 1992 and 1993 with approximately 1000 suspect cases reported per week. Currently the number of cases reported per week is 100 or less. This decline is largely a reflection of the control measures, especially certain feed bans which were enacted in 1988 and thereafter. BSE is a member of the family of disease known as the transmissible spongiform encephalopathies (TSEs). Other related animal diseases include scrapie of sheep and goats, chronic wasting disease (CWD) of deer and elk, transmissible mink encephalopathy (TME), feline spongiform encephalopathy (FSE), and TSEs of exotic ruminants.
Many of these diseases are either known to be inter-related or speculation of causative inter-relationships exist. For example, evidence indicates that FSE and the TSE in exotic ruminants was caused by the feeding of BSE contaminated products to these species. There is also evidence that a new variant of Creutzfeldt-Jakob Disease, a human TSE was caused by the BSE agent. It has been postulated that scrapie started the above chain of events being the underlying cause of BSE. Although no case of BSE has been detected in the United States, trade has been impacted by the existence of scrapie, TME, and CWD which are cited as risk factors.
BSE strictly as a disease entity has been reported to have clinically affected less than 200,000 head of cattle worldwide in a 12-year period of time. The other diseases have been reported at even lower levels. These are relatively small in comparison to deaths and other losses from highly infectious, contagious diseases such as Foot and Mouth Disease (FMD). The primary impacts on the world animal health situation have been in the areas of a likely or speculated human health link, various regulatory controls, trade, consumption, public perception about animal health, research, and economics.
For diseases that have had little impact on actual animal health, millions of dollars have been lost by countries involved in the trade of animals and animal products (even those without BSE). These diseases have also caused the loss of consumer confidence in the food supply and governmental controls in a number of countries.