Variant of mad cow disease may be transmitted by blood transfusions, according to animal study

August 28, 2008

Blood transfusions are a valuable treatment mechanism in modern medicine, but can come with the risk of donor disease transmission. Researchers are continually studying the biology of blood products to understand how certain diseases are transmitted in an effort to reduce this risk during blood transfusions. According to a study in sheep prepublished online in Blood, the official journal of the American Society of Hematology, the risk of transmitting bovine spongiform encephalopathy (BSE, commonly known as "mad cow disease") by blood transfusion is surprisingly high.

BSE is one of a group of rare neurodegenerative disorders called transmissible spongiform encephalopathies (TSEs), and there is no reliable non-invasive test for detecting infection before the onset of clinical disease. In addition to BSE, these diseases include scrapie, a closely related disease in sheep, and Creutzfeld-Jakob disease (CJD) in humans, which causes neurological symptoms such as unsteadiness and involuntary movements that develop as the illness progresses, rendering late-stage sufferers completely immobile at the time of death.

A new variant of CJD (termed vCJD) was recognized in the United Kingdom in the mid-1990s, apparently as a result of the transmission of BSE to humans. Because the symptoms of this disease can take many years to appear, it was not known how many people might have been infected, and without a reliable test for identifying these individuals, clinicians were very concerned that the infection could be transmitted between people by blood transfusion or contaminated surgical and dental instruments. As a result, costly control measures were introduced as a precautionary measure to reduce the risk of disease transmission, although at the time it was unclear whether there really was a significant risk or whether the control measures would be effective. This sheep study sought to better understand how readily TSEs could be transmitted by blood transfusion in order to help develop more targeted controls.

"It is vitally important that we better understand the mechanisms of disease transmission during blood transfusions so we can develop the most effective control measures and minimize human-to-human infections," said Dr. Fiona Houston, now a Faculty of Veterinary Medicine, University of Glasgow, UK, and lead author of the study.

The nine-year study conducted at the University of Edinburgh compared rates of disease transmission by examining blood transfusions from sheep infected with BSE or scrapie; the BSE donors were experimentally infected, while the scrapie donors had naturally acquired the disease. While scrapie is not thought to transmit to humans, it was included as an infection acquired under field conditions, which could possibly give different results than those obtained from experimentally infected animals. Because of the similarity in size of sheep and humans, the team was able to collect and transfuse volumes of blood equivalent to those taken from human blood donors.

The outcome of the experiment showed that both BSE and scrapie could be effectively transmitted between sheep by blood transfusion. Importantly, the team noted that transmission could occur when blood was collected from donors before they developed signs of disease, but was more likely when they were in the later stages of infection. Of the 22 sheep who received infected blood from the BSE donor group, five showed signs of TSEs and three others showed evidence of infection without clinical signs, yielding an overall transmission rate of 36 percent. Of the 21 infected scrapie recipients, nine developed clinical scrapie, yielding an overall transmission rate of 43 percent.

Investigators noted that the results were consistent with what is known about the four recorded cases of vCJD acquired by blood transfusion in humans. In addition to the stage of infection in the donor, factors such as genetic variation in disease susceptibility and the blood component transfused may influence the transmission rate by transfusion in both sheep and humans.

"The study shows that, for sheep infected with BSE or scrapie, transmission rates via blood transfusion can be high, particularly when donors are in the later stages of infection. This suggests that blood transfusion represents an efficient route of transmission for these diseases," said Dr. Houston. "Since the results are consistent with what we know about human transmission, the work helps justify the control measures put in place to safeguard human blood supplies. It also shows that blood from BSE- and scrapie-infected sheep could be used effectively in non-human experiments to answer important questions, such as which blood components are most heavily infected, and to develop much-needed diagnostic tests."

Source: American Society of Hematology

Explore further: How rogue immune cells cross the blood-brain barrier to cause multiple sclerosis

Related Stories

How rogue immune cells cross the blood-brain barrier to cause multiple sclerosis

November 21, 2017
Drug designers working on therapeutics against multiple sclerosis should focus on blocking two distinct ways rogue immune cells attack healthy neurons, according to a new study in the journal Cell Reports.

One health researchers identify hot spots of tick-borne diseases in Mongolia

November 16, 2017
Given the critical role livestock play in Mongolia, transmission of tick-borne diseases can have very real health and economic implications for livestock and the herders that tend to them. Dr. Michael von Fricken explored ...

ACP and CDC issue recommendations for hepatitis B screening, vaccination, and care

November 20, 2017
Reducing chronic hepatitis B infections by screening at-risk adults, increasing hepatitis B vaccination rates, and linking infected persons to care is a public health priority, the American College of Physicians (ACP) and ...

Research reveals biological mechanism of a leading cause of childhood blindness

November 16, 2017
Scientists at the Virginia Tech Carilion Research Institute (VTCRI) have revealed the pathology of cells and structures stricken by optic nerve hypoplasia, a leading cause of childhood blindness in developed nations.

New study finds extra bite of blood transforms invasive Asian tiger mosquito from poor to potent spreader of Zika virus

November 7, 2017
The invasive Asian tiger mosquito now rapidly spreading in parts of the United States and Europe may have been significantly underestimated as a potential source of Zika and dengue virus infections—and for one simple reason: ...

Comprehensive health study in India finds rise of non-communicable diseases

November 14, 2017
A new state-by-state health analysis in India finds that over two decades heart- and lung-related conditions, as well as other non-communicable diseases (NCDs), have surpassed infectious diseases, such as diarrhea and tuberculosis, ...

Recommended for you

Rainfall can indicate that mosquito-borne epidemics will occur weeks later

November 22, 2017
A new study demonstrates that outbreaks of mosquito-borne viruses Zika and Chikungunya generally occur about three weeks after heavy rainfall.Researchers also found that Chikungunya will predominate over Zika when both circulate ...

Alcohol consumption and metabolic factors act together to increase the risk of severe liver disease

November 22, 2017
A new study provides insights into the interaction between alcohol consumption and metabolic factors in predicting severe liver disease in the general population. The findings, which are published in Hepatology, indicate ...

Gastric acid suppressant lansoprazole may target tuberculosis

November 21, 2017
A cheap and widely used drug, used to treat conditions such as heartburn, gastritis and ulcers, could work against the bacteria that cause tuberculosis (TB), according to new research from UCL and the London School of Hygiene ...

Improving prediction accuracy of Crohn's disease based on repeated fecal sampling

November 21, 2017
Researchers at the University of California San Diego Center for Microbiome Innovation (CMI) have found that sampling the gut microbiome over time can provide insights that are not available with a single time point. The ...

Anti-malaria drug shows promise as Zika virus treatment

November 17, 2017
A new collaborative study led by researchers at Sanford Burnham Prebys Medical Discovery Institute (SBP) and UC San Diego School of Medicine has found that a medication used to prevent and treat malaria may also be effective ...

Decrease in sunshine, increase in Rickets

November 17, 2017
A University of Toronto student and professor have teamed up to discover that Britain's increasing cloudiness during the summer could be an important reason for the mysterious increase in Rickets among British children over ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

NewDimension
not rated yet Aug 30, 2008
I'am very shocked about the risk evolved with mad cow disease. Why are there not more protective measurements for the population like testing 100% of all meat before sale? Just that the mad cow disease in humans take many years to develop does not mean that there is nobody infected with. The situation reminds on the HIV problems where a few ill didn't trigger a large response.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.