No risk has been detected linking neurological surgical instruments with the transmission of Creutzfeldt-Jakob Disease, but a British doctor recommends a better safe than sorry policy.
Transmissible spongiform enceph-alopathies are a challenge for public health because the agents causing these brain-destroying diseases are nearly indestructible, Dr. Robert Will of Western General Hospital in Edinburgh said in Calgary Feb. 19 during the PrioNet annual meeting.
International scientists met to discuss the pathology and social impacts of prion related diseases such as CJD, BSE and chronic wasting disease.
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The agents, which are also known as prions, appear resistant to sterilization so there is concern the infection could persist on surgical instruments, blood products and organ transplants.
“This is a challenge for all of us trying to deal with CJD,” said Will, who talked about how risk is managed to control the human form of transmissible spongiform enceph-alopathy in Great Britain.
He said scientists know there are diverse types of the disease that can be transmitted, inherited or occur sporadically. The disease is named after two German scientists who first described it in the 1920s.
Classical CJD is of short duration, and scientists have been able to separate several types of the disease based on molecular features rather than clinical symptoms.
Canada reports 35 to 40 cases of the classical form of the disease a year.
Variant CJD is found in the tonsils, spleen, lymph nodes and brain and has been linked to eating BSE-contaminated beef.
About 165 people have died of this strain. Most were in Great Britain.
No new cases of variant CJD have been diagnosed in anyone born after 1989.
No cases of maternal transmission have occurred, but scientists are curious about surgical transmission, blood transfusions and organ transplants.
A blood transfusion study was conducted in 1996.
Scientists suspected three or four cases of the disease were linked to blood transfusions when donations came from people who later developed vCJD. In some cases people died from other causes after receiving the transfusions. Scientists do not believe these medical practices could affect many people.
Plasma appeared to present a greater risk so Britain has not produced plasma products since 1999. Instead, the products are imported from the United States.
Some people have been advised not to donate blood and the country’s medical community launched an education campaign on the use of blood and tissues in medical procedures.
The disease has not been detected on surgical instruments but scientists believe there could be a risk on those used in neurology. They advise destroying them as a precautionary measure.
Besides assessing risk factors, scientists want to compile a detailed and reliable classification system for prion diseases to reduce the chance of misdiagnosis, identify new forms and provide better surveillance of cases.
The system should also identify atypical forms of the diseases, said Pierluigi Gambetti of the National Prion Disease Pathology Surveillance Center in the United States.
The centre has looked at a number of these diseases, including transmitted forms such as variant CJD, kuru, which is caused by cannibalism, and sporadic and inherited forms of the disease.
Research is also looking at zoonotic possibilities such as chronic wasting disease to see if there is a human health connection. It appears to be spreading among farmed and wild deer and elk and no one is sure how it happens.
Studies were done among deer and elk hunters who developed CJD. All cases were the classical type with no evidence of it crossing the species barrier.
Work on mice expressing elk prion protein contracted CWD but the humanized mice did not develop it.
“We could not find any typical case or shift that point to the presence of a case or the potential for transmission of chronic wasting disease to humans to occur,” Gambetti said.
“That does not mean transmission will never occur.”
The centre is also seeing a new human prion disease that appears to affect the frontal lobe, leading to dementia. CJD is usually found in the cortex of the brain. The vacuoles found in brain tissue appear larger than classical CJD.
