WHO Tables on Tissue Infectivity Distribution in Transmissible Spongiform Encephalopathies

Overview

The data reported in the ‘‘WHO Tables on Tissue Infectivity Distribution in Transmissible Spongiform Encephalopathies’’ were originally assembled by an expert group appointed during a WHO Consultation held in 2003 and subsequently updated during a WHO Consultation held in 2005 (see References section). As new information became available,
the group updated the tables and they now reflect the current status of knowledge about infectivity in body tissues, secretions, and excretions of humans with sporadic or variant Creutzfeldt-Jakob disease (CJD); cattle with typical or atypical bovine spongiform encephalopathy (BSE); sheep with scrapie; and (for the first time), deer or elk with Chronic
Wasting Disease (CWD). It is not the purpose of this document to revise the current ‘‘WHO Guidelines on Tissue Infectivity Distribution in Transmissible Spongiform Encephalopathies’’ published in 2006, which remain valid, but the new information on tissue infectivity distribution reported here is important in the context of potential transmission of variant CJD through human blood and blood products, as well as through medicinal products prepared with bovine-derived materials, and may have implications for future recommendations.

Since the publication in 2006 of Annex 1 (Major Categories of Infectivity) in the ‘‘WHO Guidelines on Tissue Infectivity Distribution in Transmissible Spongiform Encephalopathies’’, some tissues (ovary, uterus, mammary glands/udder, skin, adipose tissue, and heart/pericardium) and body fluids (saliva, milk, urine, and feces) in which infectivity had not been detected, have since been found to contain infectivity or PrPTSE and therefore have there been moved from the category of ‘‘tissues with no detectable infectivity’’ ’’ to the category of ‘‘lower-infectivity tissues.’’