Bovine spongiform encephalopathy (BSE), popularized in the recent press coverage of the European epidemic as "mad cow disease," belongs to a group of progressively degenerative neurological diseases, collectively known as transmissible spongiform encephalopathies (TSE’s)(See Table 1.) TSE’s are characterized by long incubation periods, short clinical course, 100% fatality, and no known course of treatment. The causative agent has not been fully characterized; however, resistance to physical and chemical agents that destroy nucleic acids essentially rules out conventional microbial and viral agents. The scientific community is increasingly referring to the "prion" theory as the most likely source of infection. The infection seems to be dependent on the infected animal’s own proteins, while the lack of foreign proteins allows the infectivity to remain invisible to the host’s immune system. This "invisibility" fails to provoke an antibody response, which. causes the development of typical vaccines and simple detection techniques to likely be improbable. The current test, other than post-mortem histopathology, involves the isolation of the appropriate suspected infected tissue (brain and other nervous tissue being best), injecting it into mice and waiting about 700 days for any symptoms to develop. The peculiar nature, invisibility, of the disease explains the possibility of spontaneous mutation as well as the spread from exposure, as this disease has the peculiarity of being both an acquired infection and a Mendelian inherited disease, generally considered inconsistent with an infectious agent. Additionally, the vulnerability of one species versus another varies considerably. A number of domestic cats (>86) in Great Britain have contracted encephalopathy; however, not a single dog, pig or horse have, despite exposure to the same agents thought to have transmitted the disease to the cats.
That's almost 2 years; do mice really live that long?