Vol. 5, Issue 6, Part A (2020)

Author(s): JB Kathiriya, NM Shah, SH Sindhi, BJ Trangadia, MM Tajapara, AA Vagh and KR Bhedi

Abstract: Transmissible spongiform encephalopathies (TSEs) or prion diseases are a group of fatal neurodegenerative diseases caused by prions (PrP^Sc). The Prion proteins are devoid of any nucleic acid and have molecular weight of approximately 30 kDa. These exist in two forms: a normal cellular prion protein (PrP^C) and a pathogenic misfolded conformer (PrP^sc). The disease affects a variety of animal species, including human. Prions derive from a conformational conversion of the normally folded prion protein (PrP^C) and acquire pathological and infectious features which is still not well understood. The infectious prion proteins cause mammalian TSEs including Scrapie (sheep), Chronic Wasting Disease (deer and elk), Bovine Spongiform Encephalopathy (BSE; cattle) and Creutzfeldt-Jakob Disease (CJD; human).The prion diseases are generally characterized by a long incubation period, usually in years, a relatively short clinical course and without exception, they cause dementia, loss of motor control, paralysis and ultimately death. The prion accesses the central nervous system (CNS) through autonomic nerves, directly after intracerebral inoculation, or via aerosols through immune-independent pathways. During the course, they first colonize and replicate in secondary lymphoid organs (SLOs). At present, a reliable diagnosis of prion disease is possible only through autopsy since all ante mortem tests are less sensitive. The commonly used diagnostic tests are ELISA, IHC and immunoblotting. A histopathological test is generally performed for confirmation. However, the final confirmation is obtained by a bioassay to assess the infectivity of the pathogen. This is the most sensitive test and infectivity in transgenic mouse to detect pathogenic PrP^d. The prevention and control measures adopted for the bovine spongiform encephalopathy are surveillance, culling of sick animals, banning specified risk materials or BSE supplement. The most stringent control measures include a UK program that excludes all animals more than 30 months of age from the human food and animal feed supplies. The program appears to be highly effective. Other control measures include banning the use of mechanically recovered meat from the vertebral column of cattle, sheep and goats for human food and BSE testing of all cattle more than 30 months of age destined for human consumption. All these strategies have worked successfully in controlling the BSE outbreaks in Europe and other part of world.