nvCJD reaches 81 in 3 countries
Finally...an unselected autopsy series
CJD girl's mother warns of `nightmare waiting to happen
BSE case raises new fears over transmission
Patient of Possible Mad Cow Disease Dies in Venezuela
EU adopts ban on BSE-risk cattle tissues
Four herds killed as France reports new BSE cases
Meat with scab, pus and tumors is OK, USDA say
Acquiring CJD from blood transfusions:a systematic review
10 July 00 webmaster UK Dept of Health Victim count updated to 31 July 00Statistics released last week by the UK Dept of Health for the first half of 2000 show 74 victims of nvCJD, including 4 new cases for the month of June. There are additionally 2 confirmed deaths in France and 1 in Ireland. The total includes 6 probable deaths from nvCJD where neuropathological confirmation will never be possible (lack of family permission) and 3 cases where the victim is still alive. The next table will be published on Monday 7 August 2000.
The improved reporting system (inclusion of still living/deceased but not autopsied cases) makes for comparion to the old system difficult and thus complicates trend analysis. This showed up in Mar 2000 statistics when 15 cases were released. These 15 cases were not back-assigned to the month they would have belonged to had the new system always been in effect, creating a hiccup in the tables. There have been 7 cases added in the 3 months since the new system started, annualizing to 28. But we won't have complete onset data for 2000 until July 2001.
Under their old system, some of these cases would never have been included (no autopsy), others would have been included only after autopsy (that is, detected 6 months after onset, 9 months to death 15 months after onset, 3 months to autopsy = 12 months later). Date of onset is the best tracking datum but it is not given for the new However, enough onset data has been released in various pubic forums for the webmaster to construct the graph below. Note that the onset data are far better fit by a second order curve than a straight line. It cannot be determined from this where the case load is headed long term; the fresh-tissue tonsil survey is a far better way to proceed.
The best system is simply to list by case number in reverse chronology by date of onset. This allows a consistent chart to be immediately drawn and any trend determined. Probably all of the 7 new cases in 2000 had date of onset in 1999 because the known onsets stopped in June 99 and there is 6 months on average from onset to detection.
1994 8 + 0 = 8 1995 10 + 0 = 10 1996 10 + 1 = 11 1997 13 + 0 = 13 1998 8 + 5 +1 = 14 1999 3 +6 +7+2 = 18 bringing total to 74 2000 first cases with onset in this year would be detectable in July. 20 cases might be expected with onset in 2000.
Prion protein immunoreactivity in brain samples from an unselected autopsy population: findings in 200 consecutive cases. Neuropathol Appl Neurobiol 2000 May;26(3):273-284 Esiri MM, Carter J, Ironside JW Radcliffe Infirmary, Oxford, UK and CJD Surveillance Centre, Western General Hospital, Edinburgh, UK.[Opinion (webmaster): This is quite an interesting study in various ways. There has been great reluctance in all countries to determine actual incidence of CJD through random autopsy series. CJD is different from other diseases in that it is dangerous even if it has not become a clinical problem at the time of death. It is possible that the normal aging human brain contains a small amount of infectious prion amyloid, just as it often contains Alzheimer amyloid.
Reading the abstract literally, that a case of nvCJD shows up as one of an "unselected group of 200 post-mortem cases" has alarming statistical implications. Puzzlingly, was this clinical diagnosed case not referred to the Surveillance Centre or was it and then got into the unselected group?
The thrust of the article is more to false positives, or rather that the antibody is detecting variable amounts of normal prion protein in non-cases, unlike in their 1998 paper (the only other place monoclonal KG9 appears) ]
"Immunostaining for prion protein (PrP) using the KG9 monoclonal antibody was undertaken on brain sections from an unselected group of 200 post-mortem cases. One case of clinically diagnosed nvCJD was confirmed and showed widespread abundant PrP immunostaining with KG9 and somewhat less abundant PrP with another monoclonal antibody, 3F4.
PrP immunostaining seen with KG9 was insensitive to proteinase K pretreatment in sections from this case of vCJD. Among the remaining 199 cases, sections from 84 (42%) showed small amounts of PrP immunoreactivity with the KG9 antibody, mainly localized to neurones, neural processes and argyrophilic plaques of the type seen in ageing and Alzheimer's disease. Purkinje cells, swollen (ischaemic) axons, macrophages and microglials cells were also occasionally labelled with this antibody in non-CJD cases. Pre-treatment of adjacent sections from non-CJD cases with positive KG9 staining abolished this staining, indicating that it represented the cellular form of PrP.
There were differences in age, sex and cause of death in non-CJD cases with some PrP immunostaining patterns compared with cases lacking any staining. Specifically, a younger mean age, more females and fewer cardiac deaths were found among those with neuronal PrP staining patterns. Staining of some features was also significantly associated. These findings need to be taken into account when PrP immunostaining is used to diagnose prion diseases. They may indicate that cellular PrP is increased in the human brain under some circumstances and provide insight into the handling of this protein by human brain cells."
Thromb Haemost 1998 Dec;80(6):909-11 Lee CA, Ironside JW, Bell JE, Giangrande P, Ludlam C, Esiri MM, McLaughlin JE" In 1996, the CJD surveillance unit in Edinburgh, UK described nvCJD which was thought to be the human equivalent of bovine spongiform encephalopathy (BSE). The identification of prion protein in the tonsil of an affected individual has raised the question of transmission of nvCJD via blood products. This study examines the post mortem brains of 33 patients who were treated with clotting factor concentrate of predominately UK donor source during the years 1962-1995.
The brains were examined by conventional histological methods and also for the prion protein using monoclonal antibodies KG9 and 3F4. No evidence of spongiform encephalopathy was found and the immunocytochemistry was negative for PrP in all cases. It is concluded that, at present, there is no evidence for the transmission of nvCJD via clotting factor concentrate to patients with haemophilia."
Fri, Jun 30, 2000 By Nick Allen, PA NewsThe mother of a schoolgirl who died from the human form of mad cow disease warned today that the condition was "a nightmare waiting to happen".
Claire McVey, 15, died on January 11 this year from variant Creutzfeldt-Jakob disease after months of illness. She is thought to be the youngest person to die from the disease which has so far claimed 52 lives in Britain.
A verdict of misadventure was recorded today at an inquest in Barnstaple, Devon. Following the inquest Claire's mother Annie McVey, of Kentisbury Ford, Devon, said: "This time last year I had everything. But I didn't spend Claire's 16th birthday going Formula One racing as we had planned or having sweet 16 parties, I spent it at her graveside. This time next year this could be you. It's a nightmare waiting to happen and until the next 20 or 30 years of incubation we won't know."
In a statement read to the inquest, Mrs McVey, a registered nurse, described how she spent up to 24 hours a day caring for her "amazing" daughter. Claire had danced with the English National Ballet and was a good netball player and swimmer, she said. She had set her sights on a career as a lawyer in the United Sates.
In March last year she became moody and depressed but initially her mother thought it was to do with two close relatives dying, and moving to a new house. Mrs McVey said: "The effects on our household were total chaos and increased instability. She was abusive at home and admitted feeling thick and out of control."
Claire began breaking things around the house and scratched a long mark in the coffee table. "She was unable to explain why but she looked panicked and anxious. A couple of outbursts in public shocked me. I couldn't understand how she could change so quickly," her mother said.
Claire asked her mother to write to her school, Ilfracombe Community College, so she could wear trainers instead of shoes because she felt unsteady on stairs. She was taken to her GP and in August was referred from North Devon District Hospital to Fenchay Hospital in Bristol, where doctors searched for a diagnosis.
Mrs McVey said: "My daughter was amazing. I think she was relieved when she found out something physical was wrong and it wasn't just her being weak-willed. Discussions about death and dying happened every day."
"On August 28 Claire made her will and funeral arrangements and discussed her fears about dying and death. She told me how she wanted us to die together. This was only 25 days after she saw a consultant at North Devon.
"She had walked into Frenchay two weeks earlier but she left in a wheelchair. The deterioration took my breath away and a year later I'm still reeling from the rapidity of her decline."
She spent the last two weeks of her life in the Littlebridge House hospice. "We were with her for her last breath," said Mrs McVey. Recording a verdict of misadventure, North Devon Coroner Richard van Oppen said she had died after a "random consumption" of a meat product contaminated with BSE.
Thu, Jun 29, 2000 By Rachael Crofts and Trevor Mason, PA NewsFears of a new food scare were being played down today after a cow born after the introduction of controls to eradicate BSE was found to be suffering from the disease.
The Government has ordered a special investigation into how the cow caught the disease amid fears it could have been passed on by the animal's mother - a method of transmission not previously proved. Ministers insisted there was no risk to food safety. But food safety experts said the case raised new concerns about the spread of the disease and called for a "transparent" investigation.
The Holstein cow, born on August 25 1996 and from the Dorset area, was confirmed as a BSE case on Tuesday, Agriculture Minister Nick Brown told MPs. The birth date is significant because it was after August 1 1996, when extra control measures on animal feed containing mammalian meat and bone meal were implemented.
Mr Brown said there was some evidence that the cow had caught the disease from its mother, but that did not rule out a rogue batch of contaminated feed as a possible route. Experts had predicted 19 cases of BSE in cattle born after August 1 1996 before the end of the year, yet this was the only one so far.
He stressed that because the animal was 44 months when it died, there was no possibility that it could have entered the food chain as anti-BSE regulations forbid the use of animals aged over 30 months in food production. He said: "The case does not change in any way our view that we have the toughest rules in place to protect public health and eradicate the disease."
Dr Tim Lobstein, co-director of the Food Commission said: "Until more is known, we do not know how this cow got the disease - but it raises alarming possibilities that new methods or forms of transmission have yet to be fully appreciated by Government scientists."
The Consumers' Association said: "There needs to be a thorough and transparent investigation as to how the cow became infected and any implications for public health.
"This again reinforces the fact that many uncertainties still remain regarding BSE. We need to ensure that vigorous and effective controls are in place."
Official said the mother of the cow had not been identified as a suspected BSE victim.
Wed, Jul 5, 2000 COMTEX NewswireCARACAS - A Venezuelan woman has died possible due the mad cow disease, a report from the Health Ministry said on Wednesday.
Gloria Coromoto Segovia, born May 25, 1951, died Tuesday at the Uyapar Hospital of Puerto Ordaz, Venezuela, possibly a victim of the Creutzfeldt-Jakob disease -- the mad cow disease.
She had been diagnosed as a carrier of this disease by three health centers of the country, the first confirmed case in Venezuela, according to the ministry's report.
Segovia suffered in January of 2000 insomnia, numbness of the tongue, involuntary twitching of her arms. She had been unconscious for the last days, with her eyeballs turned upward and with convulsions, completely indifferent to her surroundings.
[Opinion (webmaster): In all liklihood, the woman here was a victim of sporadic or familial CJD. There is no indication of exposure to BSE or reason to suspect nvCJD. This has become typical of news accounts worldwide -- mad cow disease, a better known term, has come to supplant Creutzfeldt-Jakob Disease as the name for this disorder, even for cases having nothing to do with cows. The public unfortunately often infers a connection to BSE. That being said, the ultimate cause of sporadic CJD is not known and might in fact be dietary, though not necessarily beef.]
Fri, Jun 30, 2000 Reuters World ReportThe European Commission said on Friday it had officially adopted new rules banning from the food chain cattle tissue thought to carry mad cow disease. The move, effective from October, outlaws the use of so-called Specified Risk Materials (SRMs), such as cattles' eyes, spinal cords and brain tissue, in food and animal feed.
A majority of EU farm ministers backed the decision at their meeting on June 19. There were insufficient votes at the time for the measure to be adopted immediately but enough for the Commission to take the decision itself.
Certain member states were unhappy with the proposal because it would add to costs at slaughterhouses. "The benefits in terms of food safety and public health in the longer run far outweigh the short-term economic cost," EU Health and Consumer Protection Commissioner David Byrne said.
Under the proposal, EU countries will be divided into hig-risk and low-risk. Countries such as Britain and Portugal, which are classed as having a high rate of mad cow disease, or bovine spongiform encephalopathy (BSE), would have a long list of SRMs to remove. Others would have a shorter list.
Some member states such as Britain already remove SRMs, but according to EU officials, the measure will mean extra controls in Sweden, Finland, Germany, Austria, Spain, Italy and Greece. BSE-infected meat products are believed to cause a new form of the deadly brain-wasting Creutzfeldt-Jakob disease in humans, which has so far killed more than 70 people in Britain.
Brussels, 30 June 2000 EU press releaseThe Commission has adopted a Decision requiring all Member States to remove animal tissues which could present a BSE risk from the feed and food chain as of October 1st. The final adoption of this key consumer health protection measure was made possible after a major breakthrough in the 19 June Agriculture Council where a majority of the Member States supported the measures. From October onwards all slaughterhouses, meat cutting and animal waste processing plants throughout the EU will have to work according to the new harmonized rules. Meat imports from third countries will be subject to similar requirements as of 1 April 2001, unless scientific assessment indicates such measures are not necessary.
"This Decision and the new requirements on BSE monitoring and testing are delivering the highest possible health protection standards to European citizens. The benefits in terms of food safety and public health in the longer run far outweigh the short-term economic cost. The necessary adaptations in the working practices in slaughterhouses to remove basic specific risk materials are already in place in several Member States," said Health and Consumer Protection Commissioner David Byrne. "My next aim is to see the essentials of this safeguard measure incorporated into the proposed Council and European Parliament Regulation for the prevention and control of certain transmissible encephalopathies this autumn. We also have to establish the situation for each individual third country wanting to import meat into the EU ensuring that the measures are based on solid scientific assessment, consistent and proportional to the BSE risk."
The Decision requires slaughterhouses and authorized meat cutting and animal waste processing plants in all Member States to discard the tissues most likely to present a BSE risk:
- the skull (including the brains and eyes), the tonsils, the spinal cord and the ileum of cattle above 12 months; - the skull (including the brains and eyes), the tonsils and the spinal cord of sheep and goat above 12 months; - the spleen of sheep and goat of all ages.In the UK and Portugal slaughterhouses and authorized meat cutting and animal waste processing plants are, given their higher BSE risk, in addition required to remove:
- the entire head (excluding the tongue and including the brains, eyes, trigeminal ganglia and tonsils), the thymus, the spleen, the intestines and the spinal cord of cattle above 6 months; - the vertebral column (including dorsal root ganglia) of cattle above 30 months.The Decision also prohibits the use of certain slaughtering techniques which entail a risk of contamination of animal blood by the release of BSE infected tissue into the bloodstream as of 31 December 2000....
Mon, Jul 3, 2000 Reuters World ReportFour herds of cattle were destroyed in France after the discovery of two new cases of mad cow disease, the Farm Ministry said on Monday. The discovery of two more afflicted animals brought to 23 the number of cases of the fatal, brain-wasting disease bovine spongiform encephalopathy (BSE) reported in France this year.
France now looks set to exceed the 30 cases that were discovered in 1999. One hundred and three cases of BSE have been reported in France since the epidemic was first detected in 1991.
The ministry said in a statement the infected animals were dairy cows born in October 1993 in the Ille-et-Villaine region and in August 1994 in the Vendee. Both animals were destroyed, in accordance with French law, as were four herds in which the cattle had lived. In all, 296 animals were slaughtered.
The ministry last month began testing 48,000 French cattle for BSE in a bid to measure the extent of the epidemic among its 21 million cattle. France remains locked in a legal battle with the European Commission over its refusal to lift a ban on imports of British beef because of fears it is not entirely free from BSE.
Britain has reported more than 176,800 cases of BSE, making the French epidemic look small by comparison. But while the number of BSE cases in Britain is falling, the French outbreak is widening despite measures introduced almost a decade ago to combat the spread of BSE through contaminated animal feed. [The English BSE epidemic today still dwarfs the situation in France by a factor of 100. There is no media coverage of each cow in England with BSE; only France gets this treatment. -- webmaster]
France introduced tougher controls on cattle feed in 1996 and originally predicted that BSE cases would taper off in 2001, given that the disease was thought to have a five-year incubation period.
The government has recently stopped forecasting when it expects the epidemic to die out. Many scientists believe BSE-infected meat products cause a new form of Creutzfeldt-Jakob disease, a similar fatal brain-wasting disease that has killed more than 50 people in Britain.
Sat, Jul 8, 2000 Reuters World ReportA new case of mad cow disease has been detected in Flachere, northern Isere, in the French Alps -- the first in that region, the government veterinary service said on Saturday. The herd of 63 cattle to which the infected animal belonged were slaughtered on Saturday morning, the authorities said.
The alarm was raised on June 19 and the sick animal was slaughtered two days later. The veterinary service said an autopsy confirmed the animal had mad cow disease (bovine spongiform encephalopathy or BSE) on July 4. A total of 23 cases of madcow disease have been recorded since the start of the year.
10 July 00 (Associated Press)Three new cases of mad cow disease have been discovered in three separate herds in France and a total of 432 cows were slaughtered, the Ministry of Agriculture said in a communique Monday.
The animals were found in herds in the departments of Maine-et-Loire and Finistere in western France and in the Isere region in the Alps, the ministry said. They were the 24th, 25th and 26th cases of the year.
In 1999, French authorities discovered 31 cases of mad cow disease, or bovine spongiform encephalopathy. Mad cow disease is believed to cause a similarly brain-wasting ailment in humans known as Creutzfeld-Jacob disease.
New cases of the disease are expected to break out in France until 2002, five years after authorities took rigorous measures to prevent more outbreaks. Mad cow disease has an average incubation period of five years. The French Agriculture Ministry has said it intends to start testing sick and dead cattle to find out how widespread the disease has become.
June 30, 2000 The Detroit Free Press by ELLIOT JASPIN[Opinion (webmaster): Reading this story, on has to wonder if the USDA would hold back a sheep carcass from the human food supply just because of a little scrapie.]
"In a long tale of horrors, this chapter was among the worst. A workman slips and falls into a huge vat of meat being rendered into lard at a packing plant. His bones are fished out, but his body dissolves and is eventually packaged into "Durham's Pure Leaf Lard" bound for America's kitchens. The scene from "The Jungle," Upton Sinclair's 1906 novel about conditions in Chicago's meat-packing industry, shocked the nation.
The U.S. Department of Agriculture launched an investigation to find whether such a thing had actually occurred (it had), and Congress called hearings to placate a public angry that it had practiced accidental cannibalism. The House Agriculture Committee, which convened on June 6, 1906, was soon embroiled in a debate on a bill to reform the meat industry. Everyone agreed that meat "unfit" for human consumption should be banned. But a dispute arose about how the bill should deal with something that might not hurt a person, but might be "offensive to his ideas as to what he will consume."
The bill said food should be "wholesome," a term meat industry executives tried but failed to have removed. Despite nearly a century of investigations, exposes, regulations and legislation, the debate that began that June day -- and culminated in the nation's first Meat Inspection Act, passed 94 years ago today --is still very much alive. While Congress was clear in 1906 that it was regulating both the safety and quality of meat, the USDA's new science-based inspection system may be tampering with that mandate.
Under the new inspection rules, which the government started enforcing in January 1998, traditional "poke and sniff" inspections were replaced by a series of tests intended to monitor critical points in meat processing. Now, under a set of new experimental rules, the same science-based inspection is being applied to inspections made at the time of slaughter.
While the new rules may protect consumers from food that will sicken or even kill them, the regulations against what was termed "loathsome food" in 1906 have been weakened. Under the traditional poultry inspection system, federal inspectors viewed each carcass and culled diseased birds. To make absolutely certain only healthy birds were used, samples were taken after the first round of inspections. If a single lesion was found on a sample, it immediately triggered additional testing. If more defective birds were discovered, the government clamped successively stricter controls on the plant.
By contrast, the experimental regulations say a certain percentage of birds can have defects such as sores and scabs and still be shipped to consumers. That is because the regulations distinguish between health hazards -- such as fecal contamination, which can be lethal -- and flaws such as sores, scabs, pus and tumors which, while repugnant, do not make the meat unsafe, according to the government.
Depending on the type of defect, the government may or may not take action. The new regulations say, for example, that 52 percent of the birds sampled can have sores. A matter of semantics It is clear that the people who framed the original laws governing meat and poultry were concerned not only with the safety but also the quality of food. USDA officials issued a report in 1906 that said their inspectors condemned cattle which, while not diseased, had "repugnant conditions." "Flesh showing any unusual condition is always a source of apprehension to the American public who do not care to eat meat...should it present an offensive appearance," the report declared.
At the USDA hearings, food industry executives were less squeamish. Thomas Wilson, a meat packing executive, tried unsuccessfully to weaken the language in the bill by replacing the words "unsound, unhealthful, or otherwise unfit for human food" with a simple admonition not to use carcasses "unfit for human food." The suggestion caused an uproar. One perplexed legislator told Wilson, "If it is unfit for human food, it should be condemned. If it is unsound and unhealthful, course it is unfit for human food. I do not see why you object to it."
Judge Samuel Cowan, representing Texas cattle ranchers, tried a slightly different tack. "Now the term 'wholesome' I would take out entirely," Cowan told the committee. "I would not have that in the bill, because a thing that is wholesome to you might not be wholesome to me." When the bill was debated on the House floor 13 days later, legislators paid little heed to the meat packers' objections. Words such as "wholesome" stayed in because outside the industry, one legislator noted, "no one objects to them."
Nearly a century later, USDA officials still say they are responsible for making sure that food that reaches the consumer is wholesome. But as recently as last February, whistle-blowers inside the USDA said the government was allowing diseased chickens to be turned into chicken nuggets at a Gold Kist Inc. poultry plant in Guntersville, Ala. Following the inspectors' disclosures, several school systems refused to use the chicken nuggets, and a debate ensued on what was meant by "wholesome." The inspectors at the Gold Kist plants readily acknowledged that the chicken nuggets would not hurt anyone, arguing instead that they were not wholesome.
Federal officials would not respond to repeated requests to explain what they meant by "wholesome," but their press releases emphasized that the Gold Kist products were safe. John Bekkers, Gold Kist president and chief >operating officer, said in a statement, "As we have assured our customers all along, Gold Kist Farms brand chicken products are safe, wholesome and good to eat." Purpose defeated The Gold Kist case shows that the definition of wholesomeness has become more flexible.
As part of its program to implement its science-based inspection methods, the USDA introduced its experimental inspection program last October at the Gold Kist plant. While the plant was supposedly chosen because it processed mostly young, healthy birds, farmers in the area said the flocks they were sending to the plant had been ravaged by disease for the past several years.
As one federal official later noted ruefully to investigators, "When the Guntersville plant receives birds free of disease," the experimental inspection program works well. But, he said, "When there is a high incidence of disease, complaints are raised." Because they are supposed to prod the company into policing itself, federal inspectors say, they were ordered not to take diseased chicken off the production line. That was the company's job, they were told. But the inspectors said that if the company didn't do its job, nothing much happened.
After the inspectors complained to Cox Newspapers in February about diseased poultry being sold to consumers, plant records owed a dramatic change. Just before news leaked out, the company condemned about 5 percent of its carcasses on any given day. Afterwards, the number skyrocketed to 33 percent.
Despite the testimony of its own inspectors as well as plant records, the USDA maintains that food leaving the Guntersville plant was and is "safe and wholesome." In press releases and public meetings, department officials went to great pains to point out that their new science-based inspection prevents anything harmful to humans from slipping through.
But as Nicols Fox, who has written extensively on the food industry, pointed out, "Unquestioned is whether science is even an appropriate standard for food. It is certainly not the way most people decide what to eat and what to avoid. Science might tell us that a cooked fly in our soup isn't dangerous or that sterilized manure is a safe protein ingredient in corn flakes, but neither would be acceptable to most of us."
BMJ 2000;321:17-19 ( 1 July 2000)free full text Kumanan Wilson, Catherine Code, Maura N RickettsObjective: To determine the strength of association between history of blood transfusion and development of Creutzfeldt-Jakob disease. Data sources: English and non-English language articles published from January 1966 to January 1999 were retrieved using a keyword search of Medline and Embase. These were supplemented by handsearching key journals and searching bibliographies of reviews.
Study selection: Two independent reviewers selected the relevant abstracts and articles. Articles were chosen that reported the results of case-control studies trying to identify rates of prior blood transfusion in patients with Creutzfeldt-Jakob disease and in controls. Data extraction: Odds ratios and information on study quality were extracted from the selected articles by two independent reviewers.
Data synthesis: Five studies containing data on 2479 patients were included. Three of the five studies used medical or neurological patients as controls, the other two used population controls. Odds ratios for developing Creutzfeldt-Jakob disease from blood transfusion ranged from 0.54 to 0.89. Four of the five studies had confidence intervals that crossed 1.0. The combined odds ratio was 0.70 (95% confidence interval 0.54 to 0.89).
Conclusions: Case-control studies do not suggest a risk of developing Creutzfeldt-Jakob disease from blood transfusion. Rather, a trend seems to exist towards a lower frequency of previous blood transfusion in patients with Creutzfeldt-Jakob disease than in controls. However, it is important to be aware of these studies' methodological limitations primarily the choice of control population and reliability of recall of transfusion status.
Opinion (webmaster): This was a worthwhile attempt to synthesize variously designed earlier studies; yet it is safe to say that if blood transfusions caused a few percent of sporadic CJD, as with scrapie-to-human, interview methods simply do not have the resolving power to find these cases in the sea of sporadic CJD from other causes. So inevitably there is a Scottish verdict of 'not proven' which is a very different thing from 'not guilty'.
Of course, given the incubation period and dates of the studies, these are really 20-40 year look-backs at strain types prevalent in the blood supply then, and have no relevence to, say, the risk of CWD transmission to human by hunter blood. Another concern, especially from frequent donors with extremely early onset (eg, Doug McEwen), is that a very rare or even unique strain of CJD will be catastrophically virulent (the hundred-year flood event).
Most articles of this type try to bridge the evidentiary gap with advocacy, whereas we would be better served if they simply stated the residual uncertainty in pragmatic units, eg, "we can say with 95% certainty that less than 5% of sporadic CJD arises from transfusions [resp. corneal transplants, total surgeries, eating sheep brain, etc.].
The problem here is that a conclusion even this strong probably cannot be drawn and even if it could, would cause a fair measure of anxiety in patients who then, the argument goes, would forgo some beneficial and lucrative procedure to their statistical detriment.
For every experimental paper that looks into the causes of sporadic CJD, there must be a hundred that interview friends or family of the deceased about long-forgotten meals and medical procedures. Very seldom is familial CJD ruled out -- even in the golden age of genomics with its $2 sequenator runs, no one has ever looked beyond the immediate coding sequence.
Very late onset, difficult diagnosis, and 1920's recognition of the disease mean that nothing is really known about the cause of death in parents, much less grandparents, of most CJD victims. Even in known familial CJD, the kindred is often too small. So searching for secondary genes, especially in the recessive case, is unfavorable though these have successfully been identified in Alzheimer and other amyloidoses.