[Handling of unconventional pathogens]

This article summarizes decontamination problems in handling transmissible spongiform encephalopathies (TSE) in the field of human pathology. The combination of chemical (i.e. 1 M NaOH, 1 h, room temperature) and physical (i.e. autoclaving for 30 min at 131 degrees C) decontamination methods was proven to be suitable for instruments and other materials. Als for the autopsy of suspected TSE patients, safety measures have to be taken. The brain preparation, in particular, represents a considerable risk which must be minimized by appropriate safety measures. Conventional formaldehyde fixation does not decontaminate tissues! Embedding, cutting, deparaffinization and processing or staining have to be done with cautions; members of staff must be aware of the danger. After the handling of suspect materials, the hands should be washed without brushing the skin. In the case of percutaneous inoculation the injury must be decontaminated immediately using iodine- or phenol-containing preparations, 0.5 M NaOH or 1:3000 potassium permanganate.

Bovine spongiform encephalopathy in the United Kingdom: memorandum from a WHO meeting

This Memorandum reviews the current state of research being carried out on transmissible spongiform encephalopathies (TSE) and examines the results of epidemiological studies conducted on bovine spongiform encephalopathy (BSE) and Creutzfeldt-Jakob disease (CJD) in the United Kingdom. It is concluded that the BSE epidemic is on the decline and the policies adopted in the United Kingdom are sufficient to minimize the risk of exposure to BSE of all species, including humans.

Beef and bovine spongiform encephalopathy: the risk persists

Bovine spongiform encephalopathy (BSE) is one of the transmissible spongiform encephalopathies (TSE) that are currently known to the authors to affect only mammals, including man. The diseases are progressive, fatal paralyses and dementias, for which there are no methods of certain diagnosis and no treatment. In this review the disease in cattle, the mode of transfer of these TSEs between animals by mouth, the possible presence of infective agents in the food that we eat, the resistance of BSE to cooking, and the likelihood that humans may become infected are discussed. The origins of BSE, whether from sheep, from cows, or as a mutation are considered. Whatever the origin of BSE, a substantial danger for man exists. Creutzfeld-Jakob disease (CJD), a TSE of man, may have been derived from eating infected animal tissue in the past. The possibility that this was of bovine origin and the implications that this would have for BSE infected meat in human food are discussed.

Inactivation of the unconventional agents of scrapie, bovine spongiform encephalopathy and Creutzfeldt-Jakob disease

Scrapie, bovine spongiform encephalopathy (BSE) and Creutzfeldt-Jakob disease (CJD) are the best known of the transmissible degenerative encephalopathies (TDE) that affect animals and man. Among the unusual properties of the unconventional causal agents is their relative resistance to standard decontamination procedures, and this has resulted in accidental transmission. Scrapie in sheep is the most common of these diseases and, through laboratory studies, is the best understood. As the model for the group, scrapie agent has been used in experiments to devise general standards for decontamination of the agents of the TDE.

Evaluation of NaOH treatment of human dura mater implants to obviate Creutzfeldt-Jakob disease transmission

One of the few disinfectants known to inactivate the causative agent of Creutzfeldt-Jakob Disease is NaOH. In this study, NaOH was evaluated as a possible routine treatment for human dura mater alloimplants. Use of high concentration NaOH (1 M) resulted in protein loss and macroscopic changes to the tissue. Lower concentrations (0.1 M), although exhibiting little direct detrimental effect, greatly increased the susceptibility of the tissue to collagenase digestion. The use of NaOH treated commercial or institutionally prepared human dura mater should be approached with caution.

Precautions prevent spread of Creutzfeldt-Jakob disease

Currently some experts are predicting the incidence of the rare yet rapidly fatal Creutzfeldt-Jakob disease (CJD) is on the rise. Worldwide, there is about one case per million people per year, but iatrogenic transmission is increasing. There have been documented cases of CJD transmission through corneal transplants, stereotactic equipment, human growth hormone and dura mater grafts. In addition, there are now three cases of laboratory workers with CJD from exposure in the workplace. No known treatment alters the relentless course of CJD and there is no vaccine. In every rapidly progressive unexplained dementia CJD must remain a diagnostic possibility. Because the etiologic agent is virulent, definition of necessary precautions for staff members associated with such patients is needed. Thus it is imperative medical personnel be well trained in the practice of universal precautions.

Combination ultrafiltration and 6 M urea treatment of human growth hormone effectively minimizes risk from potential Creutzfeldt-Jakob disease virus contamination

Although genetically engineered human growth hormone (hGH) is now commercially available, native pituitary-derived hGH is still used by physicians in many countries for the treatment of hormone deficiency states. We describe a method using ultrafiltration and 6 M urea that reduced infectivity in human pituitary tissue that had been deliberately contaminated with scrapie virus (an animal analogue of human Creutzfeldt-Jakob disease virus) from an initial level of 10(9.7) infectious units to just 5 infectious units. Based on estimates of the frequency of contamination and infectivity levels in batches of human pituitaries, the use of this protocol to prepare GH from cadaveric human glands yields a calculated probability of exposure to a contaminated vial of not greater than 1 in 3.2 million recipients; therefore, native hormone prepared by this method may be considered to be essentially risk-free. The same methodology may be useful in the preparation of other hormones, such as prolactin, for which no synthetic substitutes are currently available, as well as biological products derived from sheep or cattle, that may be infected with scrapie or bovine spongiform encephalopathy.

Can acquired immunodeficiency syndrome and Creutzfeldt-Jakob disease be transmitted via otologic homografts?

Materials commonly employed in the preparation of otologic homografts such as ethanol and formaldehyde are effective in vitro in inactivating human immunodeficiency virus (HIV). However, to our knowledge, the complete permeation of homograft materials with preservative has not been demonstrated. Ethanol and formaldehyde have not been shown to be effective in inactivating the Creutzfeldt-Jakob agent. The literature on sterilization procedures for these agents is reviewed. Standard procedures for preparation of otologic homografts are examined. It is recommended that donor HIV serologic status be determined when otologic homografts must be used. Further research is required to determine the efficacy of otologic homograft sterilization techniques against HIV and Creutzfeldt-Jakob disease.

Can potential hazard of Creutzfeldt-Jakob disease infectivity be reduced in the production of human growth hormone? Inactivation experiments with the 263K strain of scrapie. Rapid communication

Scrapie infectivity is reduced 5-6 logs following filtration through 100,000 MW cut-off filter plus overnight treatment with 6 M urea. These steps, applied to purified human Growth Hormone (hGH), increase the margin of safety of hGH.

Creutzfeldt-Jakob disease: implications for growth hormone deficient children

For over 25 years children with short stature due to growth hormone deficiency have been able to achieve normal height with the aid of human growth hormone (hGH) injections. Following reports of four deaths due to Creutzfeldt-Jakob disease (CJD) in young adults previously treated with hGH this treatment has ceased. There are major implications due to the potential risks of further cases of CJD and to the lack of a previously well-tried therapeutic substitute.

Precautions for Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD) is a rapidly progressive, fatal disease of the central nervous system. Premortem diagnosis may or may not be conclusive. Because the etiologic agent is virulent, definition of necessary precautions for medical staff associated with such patients is needed. Transmission of CJD in animals has been found to occur after inoculation with brain, spinal cord, liver, kidney, lung, and lymph node tissues in diminishing frequency. Effective methods of sterilization and disinfection for the etiologic agent are unknown. Thus, personnel associated with supposed-CJD patients should take precautions not unlike needle precautions for hepatitis B patients. A list of guidelines is given.

Nosocomial viral infections: III. Guidelines for prevention and control of exanthematous viruses, gastroenteritis viruses, picornaviruses, and uncommonly seen viruses

This communication is the third in a four-part series on nosocomial viral infections from the Strong Memorial Hospital. This third article discusses guidelines for prevention and control of exanthematous viruses, gastroenteritis, viruses, adenoviruses and the picornaviruses other than rhinoviruses. Several uncommonly seen viruses, such as the virus of Creutzfeldt-Jakob disease and Marburg, Ebola, and Lassa fever viruses, also are reviewed briefly.

Biohazards of investigations on the transmissible spongiform encephalopathies

There is considerable current interest in the agents that cause the spongiform encephalopathies: scrapie, transmissible mink encephalopathy, kuru, and Creutzfeldt-Jakob disease (CJD). The unusual properties of these agents, their elusiveness, and their pathogenicity for humans (in the cases of kuru and CJD) make these agents interesting subjects of investigation but also make imperative a consideration of their potential biohazards in the laboratory. In view of both the potential pathogenicity of these agents and the potential hazards of many laboratory procedures, a series of physical containment levels, each of which corresponds to a range of composite risk factors, are suggested. The estimated composite risk factor used is a function of the potential pathogenicity or relative risk factor of the agent and the potential hazard of a laboratory procedure. The lowest risk factors (1 to 2+) correspond to levels of containment similar to those recommended by the Center for Disease Control for class II microorganisms, while the highest risk factors (5 to 8+) correspond to levels similar to those for class III microorganisms. The use of such a biohazard ranking system aids in a rational approach to selection of equipment and procedures.

On the transmission of dementia: a personal view of the slow virus problem

I came across Creutzfeldt-Jakob disease within a few weeks of starting work in the neuropathological laboratories at the Maudsley Hospital. The time was the 1940's, and Alfred Meyer, who had known both Creutzfeldt and Jakob in Germany, had already published his study on the possible link between amyotrophic lateral sclerosis and Creutzfeldt-Jakob disease (or spastic pseudosclerosis of Jakob as it was then called). Meyer's interest in the condition was therefore well known to British psychiatrists and neurologists, and patients who were thought to be suffering from this illness were referred to him. Routine post-mortem examinations would be duly carried out, perhaps by the psychiatric staff, and the brain, sometimes with the spinal cord, would be hardened in formalin and sent in a parcel to the Maudsley laboratories.

Precautions in familial transmissible dementia: including familial Alzheimer's disease

Recent studies suggest that some cases of familial Alzheimer's disease may be associated with a transmissible dementia. Animal experiments show that presymptomatic carriers of "slow virus" agents can transmit disease. Because of these findings, we have extended the precautions previously delineated to include those at risk of acquiring transmissible dementia, specifically, to the descendants of those affected with familial Alzheimer's disease or familial Creutzfeldt-Jakob's disease. Blood donation from such persons may pose a danger, because transmissible spongioform encephalopathy has been passed from animal to animal by blood serum and by the WBC layer of frozen whole blood.

[Creutzfeldt Jakob disease. Recommended precautions for patient management and diagnostic procedures (author's transl)]

The virus of Creutzfeldt Jakob disease differs from conventional viruses in its extraordinary resistance to commonly used physical and chemical methods of decontamination. Autoclaving the virus for 1 hour at 121 degrees C and 2 atmospheres pressure is the most certain means for achieving total inactivation. Exposure to 5 p. 100 hypochlorite for several hours can also totally inactivate the virus, and exposure to phenol or potassium permanganate is probably effective, but as yet insufficiently tested.

Precautions in medical care of, and in handling materials from, patients with transmissible virus dementia (Creutzfeldt-Jakob disease)

We have formulated a series of precautions to be observed in caring for patients with Creutzfeldt-Jakob disease and in handling their tissues. The virus resists inactivation by simple boiling in water. Also ineffective are 10 per cent formalin, 70 per cent alcohol and ionizing and ultraviolet radiation. Autoclaving for one hour at 121 degrees C and 20 psi inactivates the agent completely. Five per cent hypochlorite, 0.03 per cent permanganate, phenolics and iodine solutions are adequate disinfectants inactivating large infective doses of the virus. Special isolation wards for afflicted patients seem unwarranted. Workers exposed to infected saliva, nasopharyngeal secretions, urine or feces need to and should wash thoroughly with ordinary soap. Needles and needle electrodes should be autoclaved or incinerated and discarded. Demented persons should not be used for donations of blood or other tissues. Although precautions are necessary, the epidemiologic evidence does not suggest an unusual risk of Creutzfeldt-Jakob disease for medical workers.

Precautions in conducting biopsies and autopsies on patients with presenile dementia. Technical note

✓Precautions are recommended for operating room and autopsy room procedures involving patients with presenile dementia. These patients may have Creutzfeldt-Jakob disease, a transmissible disease caused by a virus likely to be extremely resistant to inactivation.