What Is CJD?

'IN THIS TOGETHER'

TSE: the disease group

TSE is the abbreviation for a group of diseases called Transmissible Spongiform Encephalopathies. This rather complicated name expresses the fact that the diseases can be transmitted to experimental animals (or accidentally to humans) by inoculation or feeding of infected tissue, and that they produce myriads of tiny holes (vacuoles) in the brain, giving it a ‘spongy’ appearance under the microscope. They are thought to be caused by the proliferation within the brain of an abnormal form of protein called a ‘prion’ (shorthand for ‘proteinaceous infectious particle’), and are therefore also referred to as 'prion diseases'.

Different forms of the disease affect animals and humans. In sheep and goats, the disease is called scrapie; in mink, it is called transmissible mink encephalopathy (TME); in deer and elk, it is called chronic wasting disease (CWD), and in cattle it is called bovine spongiform encephalopathy (BSE).

TSEs affecting humans are most conveniently discussed in terms of sporadic, inherited, and environmentally acquired forms of disease. The most common form of disease is so-called 'sporadic' CJD, and was named after two German neurologists who are credited with its recognition in the early 1920’s, although it is likely that CJD had existed as an undefined cause of dementia for centuries. A familial form of CJD was discovered shortly after the first sporadic cases were reported, and subsequently other forms of familial disease were described and given different names: Gerstmann-Sträussler-Scheinker disease (GSS), and fatal familial insomnia (FFI). Kuru is the prototype human TSE, and was discovered in the 1950's among the Fore linguistic group in the interior of Papua New Guinea in the 1950's. It was spread by the practice of ritual cannibalism, and has now nearly disappeared.

The inter-relationships between these various human and animal TSEs are shown in the accompanying figure.

Figure Known and suspected inter-relationships between animal and human TSEs. TME = transmissible mink encephalopathy; BSE = bovine spongiform encephalopathy; CJD = Creutzfeldt-Jakob disease; GSS = Gerstmann-Sträussler-Scheinker disease; FFI = fatal familial insomnia.