Foreword
The announcement, in March 1996, of 10 cases of a distinct variant form of Creutzfeldt-Jakob disease (nvCJD) in young patients renewed concerns about the possibility that the bovine spongiform encephalopathy (BSE) agent could cause human disease. Research findings which have emerged since have added strong support to this hypothesis and, although many unanswered questions remain, the Government’s independent Spongiform Encephalopathy Advisory Committee (SEAC) have concluded that the transmissible agent of BSE is the same as that which causes nvCJD. The Advisory Committee on Dangerous Pathogens (ACDP) embraced this conclusion, and have recommended that BSE is defined as a biological agent within the context of the Control of Substances Hazardous to Health Regulations (COSHH).
The emergence of nvCJD, and its link to BSE, emphasised the requirement to update the previous guidance for those who work with the agent and those who may come into contact with it. Consequently, the ACDP were tasked with reviewing and revising previous occupational guidance on transmissible spongiform encephalopathies (TSEs). A priority was to review the advice to those in industrial workplaces where there is contact with material that may contain, or be contaminated with, the BSE agent, for example, those involved in animal slaughter or carcase-dressing. In June 1996, the ACDP published general occupational guidance intended to help those responsible for health and safety in developing local codes of practice for safe working.
In the light of the emerging information about TSEs, it was considered appropriate also to review and update earlier advice about laboratory work, clinical care and animal handling. The present guidance is the result of this review. It updates the 1994 ACDP publication entitled “Precautions for work with human and animal transmissible spongiform encephalopathies” and replaces previous guidance from the Department of Health on the management of patients with CJD. It is aimed at those working with animal or human TSEs in the laboratory, and provides advice also to those involved in the management and care of patients; on the handling of deceased patients; and on the minimisation of risks to other patients and staff. Inevitably, in a rapidly evolving field such as this, there will be a need to review this guidance regularly as further information becomes available.
Although the scientific community has provided considerable insights into the nature of TSEs, there are many remaining uncertainties, for example about the routes of infection, infectious dose, and the potential number of people who may be incubating nvCJD. An important factor is that nvCJD is quite distinct from classical CJD. As well as differences in clinical presentation and pathology, particularly the microscopic appearance of lesions in the brain, early indications are that the pathogenesis of the new disease may be significantly different. For example, there may be more involvement of tissues outside the central nervous system with the possibility of infectivity in other tissues or body fluids. The full implications of the differences between the different forms of CJD will need to be assessed as more information becomes available.
The assessment of risks from TSEs embraced in this document reflects these uncertainties. Research is continuing, both under a Government sponsored programme and internationally, that is aimed at improving our understanding of these unusual diseases and the agents which cause them. The results from these studies will be incorporated in future assessments of the risks.
It is important that those concerned with, or responsible for, the well-being of workers who may be at risk of exposure to TSE infectivity (and especially their employers) should ensure that they keep abreast of further scientific developments and reflect them in working practices.
Readers are reminded that this is a guide, and new findings not covered by the guidance should always be taken into account in conducting risk assessments.
This guidance has been prepared by a joint working group of the ACDP and SEAC and has been endorsed by both Committees.
The Secretariat thanks the members of the joint working group, ACDP and SEAC for their expert advice, and all others involved, including the Microbiology Advisory Committee of the Medical Devices Agency who advised particularly on decontamination issues.
March 1998
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