Prion contamination in the emergency room

prion conversionHere is a follow-up to last week’s article that described a case of variant Creutzfeldt-Jacob disease in a Texas resident caused by ingestion of BSE-contaminated beef 14 years ago.

A 59 year old male patient was admitted to the trauma unit in Lancaster, PA with a self-inflicted gunshot wound to the head. There was substantial bleeding and brain tissue extrusion from the bullet exit wound. While the patient was intubated, examination of his electronic health records revealed a previous diagnosis of Creutzfeldt-Jacob disease (CJD). After discussion with his family, the breathing tube was removed and the patient expired.

After discovering that the patient had CJD, TSE (transmissible spongiform encephalopathy) decontamination protocols were initiated. Equipment and surfaces that had been exposed to highly infectious brain tissues were identified. Because prions are extremely difficult to destroy, it was decided to incinerate many pieces of equipment costing tens of thousands of dollars. This decision was taken to protect workers in the trauma unit and future hospital patients from hospital-acquired CJD.

The usual sterilization conditions (121 degrees Celsius for 20 minutes under high pressure) do not destroy prion protein infectivity. Consequently the World Health Organization recommends incineration of potentially contaminated materials. While environmental transmission of prion diseases has not been reported, WHO suggests rinsing surfaces with sodium hydroxide or sodium hypochlorite for 1 hour, followed by flooding with water, to remove prions.

This case illustrates the problems associated with an unusual infectious agent, the prion, that is difficult to inactivate. It also shows the value of electronic health records. Without such readily accessible information, the discovery that the patient had CJD would have been substantially delayed, leading to further contamination.

Creutzfeldt-Jacob associated deaths have increased slowly but steadily in the US since 1979. The number of cases will likely continue to increase until early diagnosis tests become routinely available, and drugs are developed that can cure the disease.

Virology lecture #24: Unusual infectious agents

Download: .wmv (350 MB) | .mp4 (96 MB)

Visit the virology W3310 home page for a complete list of course resources.

A case of Creutzfeldt-Jacob disease

histology_bseThe other day I learned that a friend’s relative had recently succumbed to Creutzfeldt-Jacob disease (CJD). He told me that he had been diagnosed with the ‘infectious’ form of the disease. What does this mean?

CJD is one of several neurological diseases known as transmissible spongiform encephalopathies (TSEs). These diseases are characterized by progressive mental and physical degeneration, and by the presence of microscopic holes in the cerebral cortex (hence ‘spongiform’). The disease was described in humans in the 1920s, but was not shown to be transmissible until Carleton Gajdusek‘s work on kuru in Papua New Guinea. The disease is caused by a novel infectious agent, called a prion by Stanley Prusiner. Prions do not contain nucleic acid; rather it is the misfolding of this protein that causes the disease. CJD is extremely rare, occuring in 1 per million humans per year.

There are three major kinds of CJD. In the sporadic form, which accounts for about 85% of all cases, a spontaneous mutations likely occurs in the prion gene. About 15% of the cases are caused by inherited autosomal dominant mutations; 30 different amino acid changes leading to the disease have been described to date. The remainder are transmitted iatrogenically: originating as a result of medical care. These include the use of contaminated growth hormone derived from human cadavers, implantation of contaminated dura mater grafts, using electroencephalographic electrodes, and surgery with contaminated instruments. Prions are probably not transmitted by aerosol or casual contact. However, they may be transmitted through contact with infected tissue or body fluids. A major problem is that prions are not inactivated by autoclaving or boiling.

Variant CJD (vCJD), first described in March 1996, affects younger patients (average age 29 years, versus 65 years for CJD), has a longer duration of illness (median of 14 months versus 4.5 months) and is linked to consumption of food from cattle with bovine spongiform encephalopathy (BSE), or mad cow disease. More than 184,000 cows with BSE, and over 162 causes of human vCJD have been identified in the United Kingdom.

My friend’s relative died of infectious CJD – but he had no history of a medical procedure or transplant consistent with transmission of the disease. He worked in a hospital in New York City – but as a physical therapist, and therefore would not have had direct contact with body fluids. His age – less than 50 – is the best evidence that he had vCJD. When and where he had eaten contaminated food will never be known – perhaps on a trip to Europe in the past 5 years. What we do know, however, is that cases of vCJD in the US are extremely rare – only three have ever been reported. Now there are four.