Risk of Transmission of Prion Diseases by Blood Transfusion Upgraded
Scientists [now] say there is "an appreciable risk" of people [contracting]
the human form of BSE (bovine spongiform encephalopathy) through blood
transfusions, a significant upgrading of the threat posed by the inevitably
fatal disease [variant Creutzfeldt-Jakob disease, abbreviated as vCJD or CJD
(new var.) in ProMed-mail]. The results from tests on sheep suggest that the
danger is far more serious than first suspected. Previously the risk has
been described by the government as "theoretical".

One in six [of 24] animals given blood from infected sheep appear to have
[contracted]  disease so far [two of 6 sheep had received blood containing
BSE prions and 4 had received scrapie prions. - Mod.CP]. The experiments by
scientists at the Institute of Animal Health indicate that more blood
components than previously thought might carry the agents of BSE or vCJD,
and blood might be infective long before animals, and by extension humans,
show outward signs of the long-incubating diseases. The latest experiments
suggest that plasma and red cells might have significant infectivity.

So far there is no evidence that anyone infected with vCJD has passed it on
to others through transfusion; 22 people have received donations from 8
people who later went down with the disease, and although some of those have
died, vCJD was not considered a factor. At least 4 people with vCJD had
earlier had blood donations, but again transfusion has not been considered a

The scientists who made the transfusion of infected blood between sheep are
to report in [full in] the November issue [see below] of the Journal of
General Virology (JGV) . They say another sheep has gone down with BSE and 2
more are showing clinical signs of the disease. If those cases are
confirmed, one in 6 of the 24 sheep transfused with either whole blood or a
component will have succumbed through transfusion. [The numbers in this
report are at variance with the information in the abstract of the JGV paper
reproduced below. Previously transmission of BSE to a single sheep had been
reported, and now a second animal shows signs of disease. In addition
another 4 sheep appear to have contracted natural scrapie via blood
transfusion. - Mod.CP]

The findings, circulated to blood specialists, are regarded as enormously
significant. They have prompted urgent consideration of new measures to
protect the public and orders to hospitals to drastically reduce their use
of blood, including using technology that allows the recycling of patients'
own blood. But the Department of Health and blood transfusion services last
night appealed to the public to continue donating blood. The national blood
service, which has nearly 2 million donors in England and Wales, said: "We
still need to collect about 10 000 units a day because there are people in
hospital who rely on transfusions. We need to strike a balance between an
unknown risk and maintaining sufficient supplies."

So far 115 Britons have died and 9 others are thought to be dying from vCJD,
for which the prime culprit still appears to be contaminated meat eaten many
years ago. The government has introduced precautionary measures over blood
but it considered the risk theoretical even after autumn 2000, when
scientists in Edinburgh and Compton, Berkshire, revealed that the blood from
a sheep fed cattle brain infected with BSE had infected a previously healthy

All blood given to humans has the white cells removed because they are
regarded as potentially the most dangerous carriers of vCJD through
transfusion. Most plasma is imported because of risks to haemophiliacs who
have a constant need for the blood clotting factors.The government is
considering banning all people who have ever received transfusions from
donating blood, a decision that might remove one in 10 donors; importing
more plasma, particularly for transfusions in babies and young children; and
forcing the removal of blood platelets from plasma.

Expert advisers are expected to make recommendations within weeks, but
importing red blood cells, most widely used to replace blood lost in
surgery, would be impossible. They have a shelf life of 35 days and are in
short supply around the world.

The possibility of a blood test for vCJD next year, though essential for
public safety, might dissuade up to half Britain's donors from offering
blood, because people would have to face [the possibility of] being told
they have an incurable disease.


[The paper referred to above is entitled "Transmission of prion diseases by
blood transfusion", contributed by  Nora Hunter, James Foster, Angela Chong,
Sandra McCutcheon, David Parnham, Samantha Eaton, Calum MacKenzie & Fiona

The abstract of the paper reads as follows:
"Attempts to detect infectivity in the blood of humans and animals affected
with transmissible spongiform encephalopathies (TSEs or prion diseases) have
often been inconclusive because of the limitations of cross-species
bioassays and the small volumes of blood that can be injected by the
intracerebral route. A model has been developed for the experimental study
of TSE transmission by blood transfusion using sheep experimentally infected
with bovine spongiform encephalopathy (BSE) or natural scrapie as donors and
susceptible scrapie-free sheep as recipients. Donors and
recipients of the same species greatly increase the sensitivity of the
bioassay and in sheep large volumes of blood can be injected by the
intravenous (i.v.) route.

"Transmission of BSE to a single animal using this approach was reported
recently. This study confirms this result with a second transmission of BSE
and four new cases of transmission of natural scrapie. Positive
transmissions occurred with blood taken at pre-clinical and clinical stages
of infection. Initial studies indicate that following
such infection by the i.v. route, deposition of the abnormal prion protein
isoform, PrPSc, in peripheral tissues may be much more limited than is seen
following oral infection.

"These results confirm the risks of TSE infection via blood products and
suggest that the measures taken to restrict the use of blood in the UK have
been fully justified." - Mod.CP]

[I note that "Initial studies indicate that following such infection by the
i.v. route, deposition of the abnormal prion protein isoform, PrPSc, in
peripheral tissues may be much more limited than is seen following oral
infection."  This appears to suggest that while blood-borne transmission can
occur, it is less likely to cause disease than ingestion. - Mod.JW]

[see also:
CJD (new var.), blood donation recipients - UK 20020131.3450
CJD (new var.), blood donation restrictions - USA 20010911.2186
CJD (new var.), blood supply at risk - UK 20010707.1304
CJD (new var.), blood supply collaboration 20010706.1294
CJD (new var.), blood transfusion risk: update 20011217.3050
CJD (new var.), cluster - UK (Leicestershire) (05) 20010322.0568
CJD (new var.), contam blood prods exported - UK (02) 20010210.0278
CJD (new var.), contaminated blood prods exported - UK 20010209.0267
BSE, possibility of blood-borne transmission         20000915.1587
BSE, possibility of blood-borne transmission (02) 20000918.1604
BSE, possibility of blood-borne transmission (03) 20000919.1614
CJD (new var.), blood donation - Switzerland        20000229.0272
CJD (new var.), blood donation restrictions - Canada 20000901.1468]