Identifying CJD prions and carriers

by Nathan L. Belkin, Ph.D.

First identified in the 1920s, Creutzfeldt-Jakob disease (CJD) is a fatal degenerative disease of the central nervous system that is believed to be caused by a prion, an infectious particle smaller than a virus. It is not accompanied by an inflammatory reaction even after it finds an innocent host. The CJD prion can lay dormant for decades before any of its symptoms manifest themselves.

The methodology for identifying a carrier during this incubation period has not been available. Because of its rarity in humans, i.e., literally one in a million, the prion has never reached a point critical enough to warrant the development of a method that would make it identifiable. 

What is known to this point is that the highest concentrations of the infectious agent are found in the brain, the spinal cord and the eye. Historically, the disease has been transmitted by contaminated neurosurgery instruments, transplants (e.g., cornea transplants. and by the injection of tissue extracts (e.g., growth hormone). It is not yet known whether CJD can be transmitted by blood.

Since the agent had been found to be completely resistant to many disinfectants/sterilants, surgical instruments used on known or prospective carriers have commonly been discarded in biohazardous trash destined for incineration.1-3

Case study helps point the way

One such instance was recently reported in scientific literature and that story led to the development of a management solution regarding CJD. In it, a 43-year-old female patient who had previously undergone surgery for a herniated disc had been scheduled for repeat lumbar laminectomy. Her family history of CJD together with mutation tests identified her to be a carrier. The $5,900 set of surgical instruments originally used and described as being “near the end of their useful life” were ultimately discarded. However, since the distinct possibility exists that this patient might require laminectomies in years to come, the used instruments with high-risk tissue contact were set aside and reserved for future use for this patient only.4

Two reports of patient exposure

Historically, several reports of CJD transmission during surgery have underscored the ethical, legal and financial challenges raised by the prospect of an outbreak of this extremely serious disease. In each of the cases, neurosurgery had been performed on patients who had not been identified as carriers of the disease. Following their death, it was only a postmortem brain biopsy which first made that fact known. It is important to note that in each of these instances, the same set of neurosurgical instruments that had been used on the original patient were washed and steam sterilized after each use.5

Within the past two years, the Joint Commission on Accreditation of Healthcare Organizations. has received reports of two separate incidents at accredited hospitals where as many as 14 patients may have been exposed to Creutzfeldt-Jakob disease through instruments used during brain surgeries.6

In one particular situation, a patient who had not presented any CJD symptoms had undergone a brain biopsy to rule out vasculitis. Three weeks following the surgery, a pathology report confirmed the patient as a carrier of CJD. In the meantime, six patients had undergone brain biopsies in which the same instruments were used. Thanks to a manual tracking system that traced those specific instruments, the hospital was able to identify the patients on which these instruments had been subsequently used. This enabled the hospital authorities to take what is generally considered the ethical and right path. It informed the six patients about their possible exposure to CJD.

From its root cause analysis, the hospital came away with three important lessons they could share with other healthcare providers:

  • A CJD or prion disease patient does not always present with symptoms of CJD.
  • The time lapse between biopsy and a pathology report should be monitored and reviewed to assure shortest time from biopsy to results.
  • Instruments used in brain biopsy procedures should not be reused when a patient’s diagnosis is uncertain at the time of the procedure.

Following this incident, the hospital revised its policies and procedures as follows:

  • Follow-up on pathology reports within one week.
  • Quarantine instruments used in neurosurgery — including brain biopsies — with unknown diagnoses or uncertain diagnoses until a confirmation can be determined.

A new variant emerges

Coincidently, during this same period CJD made its presence felt in England, which triggered an enormous wave of global media attention. Although labeled as “mad cow disease,” CJD is more accurately a variant of a neurological disorder that has plagued humans for three-fourths of a century.

Since scientists were unable to determine which animals were infected with the fatal disease, British health authorities had no choice than to order all cattle destroyed. Even so, there now is concern of a human epidemic since some 900,000 cattle were eaten during the disease’s incubation period, a fact that may have exposed literally millions of people to it. Furthermore, because of the prolonged incubation period, it is possible that the true extent of the exposure to this horrible disease may not be known for as long as 10 to 20 years.7

Scientific community struggles with the challenge

At this point, it appeared that the entire infection control, microbiological and surgical communities were confronted with the challenge of staving off possible outbreaks of the disease. These relatively small numbers of occurrences, of course, still carried the potential of reaching epidemic proportions, a scenario that was naturally both unwanted and unacceptable. Thus the situation required the development of three new techniques:

  • A methodology for effectively disinfecting instruments that had been used on known carriers of CJD.
  • A way of validating the efficacy of the disinfecting process. 
  • A test that would identify a CJD carrier prior to undergoing surgery.

Disinfection and sterilization

Since conventional disinfecting/sterilization techniques have long been known to be ineffective against CJD, the community was faced with the costly possibility of having no choice other than to do away with every piece of the instruments used in neurological surgery. With the need for the development of a methodology that would eliminate such a drastic and expensive measure, the World Health Organization responded with a new set of guidelines for rendering the instruments suitable for use.8

The WHO recommendations called for the instruments to be immersed in a solution of sodium hydroxide that would be heated for 30 minutes in a gravity displacement sterilizer. The recommendations called for this disinfection process to be followed by the instruments being cleaned, rinsed in water and then subjected to routine sterilization. However, because of the hazards and problems associated with the use of sodium hydroxide (i.e., human exposure and possible damage to both instruments and sterilizer), the group also suggested two other alternate methods that use sodium hypochlorite.

Verifying the cleaning process

To assess the effectiveness of the disinfection methodology, one must consider the inactivation and removal factor — that is, the reduction of infectious units during the disinfection process. Therefore, the probability of an instrument or device remaining capable of transmitting disease would depend on the initial degree of contamination and the effectiveness of the decontamination procedure.9

A search of the scientific literature indicates that a study has been done by a group of English anesthesiologists, Miller, et al. on how to make such a determination.10

Having taken note that tonsils are known to be a storage site for the prion proteins implicated in the spread of CJD, the anesthesiologists reasoned that if the laryngeal mask airway devices used in these procedures were not satisfactorily clear of proteins before being reused, these instruments would carry a risk of CJD transmission. Thus the goal of their study was to find out whether the reusable airway devices were clear of protein material after passing through the routine cleaning efforts in their hospital (which consisted of the devices being scrubbed with a commercial detergent — containing chlorhexidine — under running tap water, drying and collective autoclaving.

Using a dye that turns red as it adheres to the bacterial protein remaining on teeth after cleaning, they found staining on each of the 20 previously used devices: 90 percent on the outer surface, 45 percent on the inner surface and 70 percent on the edges; 82 percent of the laryngoscope blades were stained and 11 percent heavily so. Staining was detected on each of the other instruments they examined including four of the five bougie tips and three of the five Magill forceps. Although not as yet validated, based on their experiences, the team concluded that “erythrosine B dye is a cheap and easy method for detecting contaminants on airway equipment and suggest that other departments use it to assess and compare the effectiveness of their cleaning methods.”

Identifying a carrier, presenting a possible solution

The ramifications of the current state-of-affairs are infinite. This is further compounded when one considers that the same disinfecting, cleaning and sterilization techniques are being recommended for use not only on devices and instruments used on known carriers, but those suspect of being carriers as well. Up until this point in time, a carrier can only be identified by either a surgical brain biopsy or an autopsy after death. Not to be overlooked is the possibility that one may be a carrier of a dormant prion(s) and therefore not even be aware of the existence of an infection. 

Researchers at the Hadassah University Hospital in Jerusalem, Israel, however, found that a precipitable and protease-resistant form of prion protein could be detected in dialyzed urine. Their experiments further suggest that the protease-resistant prion protein isoform could be excreted in urine in parallel to its accumulation in the brain. They concluded that urine testing for protease-resistant protein prion could be used not only to diagnose prion diseases in animals and humans at terminal stages of the disease but also in the subclinical stages of the infection.11,12

Based on the favorable results of initial trials by Dr. Gabizon’s research group, arrangements have been made for the manufacture of diagnostic test kits for humans and animals that will be used to confirm the efficacy of the methodology. (Personal communication: Dr. Ari Tzurket, DMD, director of research and development, Hadassah Medical Organization, Jerusalem, Israel, Aug. 11, 2002).

Pending the outcome of additional in vivo trials, the universal use of this urine test could potentially identify every carrier of this fatal disease — be they human or animal.

Nathan L. Belkin, Ph.D., a frequent contributor to HPN and other publications, is retired and living in Clearwater, FL.

REFERENCES

1. Steelman, V M, Creutzfeld-Jakob disease: Recommendations for Infection Control, American Journal of Infection Control, October 1994, Vol. 22, pp. 312-318 

2. Steelman, V M, Creutzfeldt-Jakob disease: Decontamination Issues, Infection Control and Sterilization Technology, September 1996, pp. 32-39. 

3. Steelman, V M, Prion Diseases — An Evidence-based Protocol for Infection Control, Association of Operating Room Journal, May 1999, Vol. 69, No. 5, pp. 946-967.

4. Fishman, M, Fort, GG, Mikolich, DJ, Handling of Surgical Instruments in a Presymptomatic Familiar Carrier of Creutzfeldt-Jakob disease, American Journal of Infection Control, August 2002, Vol. 30, No. 5, pp. 303-306.

5. Muscarella, LF, Assessing the Risk of Creutzfeldt-Jakob disease, Infection Control Today, August 2001, Vol. 7, No. 8, pp. 28-30. 

6. Exposure to Creutzfeldt-Jakob disease, Sentinel Event Alert, Joint Commission of Accreditation of Healthcare Organizations, Issue 20, June 2001

7. Mad cows and Englishmen: Variant CJD emerges in UK, Hospital Infection Control, September 2001, Vol. 28, No. 9, pp. 120-122

8. World Health Organization Department of Communicable Disease Surveillance and Response, WHO Infection Control Guidelines for Transmissible Spongiform Encephalopathies: Report of a WHO Consultation, Geneva, 1999

9. Rutala, WA and Weber, DJ, Creutzfeldt-Jakob disease, Recommendations for Disinfection and Sterilization, Healthcare Epidemiology, May 2001, Vol. 32, pp. 1348-1356

10. Miller, DM, Roukhana, I, Karunarathe, WU and Pearce, A, Presence of protein deposits on ‘cleaned’ reusable anesthetic equipment, Anaesthesia, 2001, Vol. 56, pp. 1069-1072

11. Shaked, GM, Shaked, Y, Kariv-Inbal Z, Halimi, M, Avraham, I and Gabizon, R, A Protease-resistant Prion Protein Isoform Is Present in Urine of Animals and Humans Affected with Prion Disease, Journal of Biological Chemistry, August 24, 2001, Vol. 34, pp. 31479-31482

12. Shaked, Y, Engelstein, R and Gabizon, R, The binding of prion proteins to serum components is affected by detergent extraction conditions, Journal of Neurochemistry, July 2002, Vol. 1, No. 1, pp. 1-5.

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February