Transmissible spongiform encephalopathies (TSE)
The appearance of a variant form of human Creutzfeldt-Jakob Disease (CJD) in the mid-1990s, as a result of the Bovine Spongiform Encephalopathy (BSE) epidemic in the United Kingdom, has increased the profile of transmissible spongiform encephalopathies as a risk to human health and has already affected public health policy worldwide. It is assumed that the variant CJD (vCJD) results from the consumption of meat products from cattle infected with BSE and that there is a relation of the incidence of vCJD to the incidence of BSE in the countries where the disease has occurred. Since 1996, over 140 cases of vCJD have occurred in UK, seven in France and one each in Ireland, Italy, USA and Canada.
Policies related to vCJD and the potential risk of human to human transmission are based on three main factors:
- an unknown number of individuals who might be infected with the BSE agent;
- presence of the pathological prion protein in many peripheral tissues from vCJD terminal patients and
- evidence of experimental transmission in animals from blood of rodents and sheep infected with vCJD and BSE respectively.
There is increasing concern about the troubling possibility that blood or blood products, vaccines and other pharmaceutical products could spread the agent of variant CJD (vCJD) worldwide, especially in countries where BSE has not yet been reported. Bovine derived materials involved in the production of vaccines and other pharmaceutical products could represent a way of potential transmission of the disease. Moreover, the possibility that human blood and plasma could be a vehicle for the transmission and spread of the disease have led to a number of donor deferral policies aimed at minimizing the risk of accepting a blood donor who might be incubating the human form of BSE. In addition, blood fractionated products such as albumin are used as stabilizers in the production of vaccines and recombinant pharmaceutical products. There is, therefore, a need to ensure that regulatory authorities with limited resources can have reliable information when making their risk assessment and evaluation of product safety to prevent the transmission of TSE to human via biological and pharmaceutical products.
A WHO Consultation was held in February 2003 to update the WHO Recommendations on Medicinal Products in relation to Human TSEs which were prepared in 1997, following a WHO Consultation on the same subject.
This Consultation complemented other important efforts of WHO in the follow up of the scientific and epidemiological developments in TSEs such as the Joint WHO/FAO/OIE Technical Consultation on BSE organized by the WHO Department of Communicable Disease Surveillance and Response (CSR) and the activities of the “Working Group on International Reference Materials for Diagnosis and Study of TSEs”, established in 1999 as a scientific forum to advance development of diagnostic tests based on available research methods and their application in health technology and pharmaceuticals.
The primary aim of this Consultation was to provide evidence-based information to medicines regulatory authorities of Member States, specially to those where BSE has not yet been reported, with regard to risk assessment, precautionary and control measures of medicinal products.
The Recommendations of the Consultation form the basis of the WHO Guidance Document to support regulatory decisions by National Regulatory Authorities in developing countries. Based on scientific information available, a tissue infectivity category was developed for the first time, that serves as a global basis for the development of risk assessment models for biological and pharmaceutical products derived from human or animal tissues or body fluids in relation to the transmission of TSE agents.
Creutzfeldt-Jakob Disease reagents
WHO Reference Reagents for In Vitro Assays of CJD Specimens. ECBS 2003. WHO/BS/03.1965 Rev.1
- Catalogue of WHO International Reference Materials (for CJD specimens see Miscellaneous)
- Distribution of WHO International Reference Materials
The characteristics of all reference preparations as well as the information regarding establishment can be found in the WHO Reference Material section.
WHO Guidelines on Tissue Infectivity Distribution in TSEs 2006
Report on International Reference Materials for Diagnosis and Study of Transmissible Spongiform Encephalopathies (TSEs). Working group fourth meeting, Geneva, Switzerland (April 2002)
Report on International Reference Materials for Diagnosis and Study of Transmissible Spongiform Encephalopathies (TSEs). Working group third meeting, Geneva, Switzerland (March 2001)
Report on International Reference Materials for Diagnosis and Study of Transmissible Spongiform Encephalopathies (TSEs). Working group second meeting, Geneva, Switzerland (May 2000)
Report on International Reference Materials for Diagnosis and Study of Transmissible Spongiform Encephalopathies (TSEs). Working group first meeting, Geneva, Switzerland (Sep 1999)
Report on WHO Consultation on Diagnostic Procedures for Transmissible Spongiform Encephalopathies (TSEs): Need for Reference Reagents and Reference Panels. Geneva, Switzerland (March 1999)