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Question: I have been hearing a lot about CJD and its potential for spreading via surgical instruments. What is CJD, and how can it be spread by instruments that have been cleaned and sterilized?

Answer: The acronym CJD stands for Creutzfeldt-Jakob Disease, an infectious, degenerative, and fatal disease of the central nervous system.(1) Creutzfeldt-Jakob Disease is one of a group of encephalopathies known as transmissible spongiform encephalopathies (TSEs). Other human forms of TSEs are kuru, Gerstmann-Straussler-Sheinker syndrome, and familial insomnia syndrome. Recently, a fourth type of human TSE called variant CJD (vCJD) has been recognized.(2) Animal forms of TSEs are scrapie in sheep and goats; transmissible mink encephalopathy; exotic ungulate encephalopathy; chronic wasting disease of mule, deer, and elk; feline spongiform encephalopathy; and bovine spongiform encephalopathy (BSE), also known as Mad Cow Disease.

The pathogenic agent responsible for CJD is highly resistant to standard sterilization and disinfection methods. Unless special protocols are used, the CJD causative agent can survive routine sterilization and disinfection processes.

Creutzfeldt-Jakob Disease is considered a slow viral infection caused by an unconventional virus known as a prion.(3) Prions are a unique class of pathogen that have no detectable DNA or RNA. These small, proteinaceous agents are abnormal isoforms of normal cellular proteins. An isoform is a group of proteins that are produced by different genes and are specific to different tissues but have the same function.(4) The cause of this transformation is unknown; however, it is thought to be a mutation of the chromosome on which the protein resides.(5)

The incubation period for CJD can vary from months to years to decades. Symptoms include rapidly progressing dementia, psychiatric and behavioral abnormalities, and a distinctive electroencephalograph reading. Positive diagnosis can be made only by direct examination of affected brain tissue. Most cases occur in patients between 50 and 70 years of age. The duration of illness after patients become symptomatic is an average of six months, and the disease always ends in death.

In contrast, vCJD has an earlier onset (ie, between 16 and 48 years of age). Patients exhibit sensory and psychiatric symptoms differing from those of CJD, and the course of illness averages 14 months. Again, the disease is always fatal.(6) According to the Centers for Disease Control and Prevention, there is strong epidemiological and laboratory evidence of a causal association between vCJD and BSE.(7) As of September 2000, no cases of vCJD were reported in the United States.

Creutzfeldt-Jakob Disease can be familial (ie, inherited in the form of a mutant gene) or sporadic (ie, no family history and no known source of transmission). Approximately 90% of cases are sporadic. Approximately 1% of cases result from person-to-person transmission and are primarily the result of iatrogenic (ie, medically related) exposure. Exposures have occurred via transplantation of central nervous system tissue, such as dura mater or corneas; repeated injections of pituitary hormone extracts; and use of contaminated surgical instruments or stereotactic depth electrodes.(8)

Tissues vary in their degree of infectivity according to prion content as follows:

* high-infectivity tissue (eg, brain, dura mater, spinal cord, corneas);

* medium-infectivity tissue (eg, cerebrospinal fluid, liver, lymph nodes, lung, kidney, spleen); and

* low- or no-infectivity tissue (eg, heart, skeletal muscle, thyroid glands, adrenal glands, intestines, peripheral nerves, bone marrow, whole blood, leukocytes, serum, adipose tissue, prostate, testis, semen, placenta, vaginal secretions, milk, tears, gingiva, nasal mucus, saliva, sputum, urine, feces).

Creutzfeldt-Jakob Disease and other TSEs are unusually resistant to conventional chemical and physical decontamination methods. The causative prions are resistant to steam sterilization, dry heat, ethylene oxide gas, and chemical disinfection with either formaldehyde or glutaraldehyde, as normally used in the health care environment. Both formaldehyde and glutaraldehyde act as fixatives, causing the prions to become more stable and less susceptible to these normal sterilization and disinfection protocols. Special protocols for instrument care after exposure to prions should be followed.(9) Table 1 is a suggested protocol for caring for instruments exposed to the CJD prion.