From: Terry S. Singeltary Sr. (
Subject: Transmission of BSE by blood transfusion in sheep...
Date: September 15, 2000 at 9:29 am PST

Subject: Transmission of BSE by blood transfusion in sheep...
Date: Thu, 14 Sep 2000 18:19:06 -0700
From: "Terry S. Singeltary Sr."
Reply-To: Bovine Spongiform Encephalopathy

######### Bovine Spongiform Encephalopathy #########

Greetings List Members,

More Dredful news, but predictable...

kind regards,
Terry S. Singeltary Sr., Bacliff, Texas USA

It is possible to transmit BSE to a sheep
by transfusion with whole blood taken from
another sheep during the symptom-free phase
of an experimental BSE infection'

It is well known that variant Creutzfeldt-Jakob
disease (vCJD) is caused by the same strain of
agent that causes bovine spongiform encephalopathy
(BSE) in cattle. F Houston and colleagues
report the preliminary findings of transfusing
blood from 19 UK Cheviot sheep fed with 5 g
BSE-affected cattle brain into Cheviot sheep from
scrapie-free flock of New Zealand-derived
animals. The investigators found BSE clinical
signs and pathology in one recipient of blood taken
from a BSE infected animal. Immunocytochemistry on
tissues taken from the transfused sheep
showed widespread PrPSC deposition throughout the
brain and the periphery. This finding
suggests that blood donated by symptom-free
vCJD-infected human beings could transmit
infection to recipients of blood transfusions.
In a Commentary, Paul Brown states that these
observations are consistent with previous reports
in experimentally infected rodents.


Research letters
Volume 356, Number 9234 16 September 2000

Transmission of BSE by blood transfusion
in sheep

Lancet 2000; 356: 999 - 1000
Download PDF (1 Mb)

F Houston, J D Foster, Angela Chong, N Hunter, C J Bostock

See Commentary

We have shown that it is possible to transmit
bovine spongiform encephalopathy (BSE)
to a sheep by transfusion with whole blood
taken from another sheep during the
symptom-free phase of an experimental BSE
infection. BSE and variant
Creutzfeldt-Jakob disease (vCJD) in human
beings are caused by the same infectious
agent, and the sheep-BSE experimental model
has a similar pathogenesis to that of
human vCJD. Although UK blood transfusions
are leucodepleted--a possible protective
measure against any risk from blood
transmission--this report suggests that blood
donated by symptom-free vCJD-infected human
beings may represent a risk of spread
of vCJD infection among the human population
of the UK.

The demonstration that the new variant of
Creutzfeldt-Jakob disease (vCJD) is caused by the
same agent that causes bovine spongiform
encephalopathy (BSE) in cattle1 has raised concerns
that blood from human beings in the symptom-free
stages of vCJD could transmit infection to
recipients of blood transfusions. There is no
evidence that iatrogenic CJD has ever occurred as a
result of the use of blood or blood products,
but vCJD has a different pathogenesis and could
present different risks. CJD is one of the
transmissible spongiform encephalopathies (TSEs)
characterised by the deposition of an abnormal
form of a host protein, PrPSc; the normal
isoform (PrPC) is expressed in many body tissues.
Available evidence, based on detection of
infectivity in blood in rodent models, and absence
of infectivity in naturally occurring TSEs, adds
to the uncertainty in risk assessments of the
safety of human blood. PrPSc has been reported in
blood taken from preclinical TSE-infected sheep,2
but it does not follow that blood is infectious.
Bioassays of human blood can only be carried out
in non-human species, limiting the sensitivity
of the test. One way of avoiding such a species
barrier is to transfer blood by transfusion in an
appropriate animal TSE model. BSE-infected sheep
harbour infection in peripheral tissues3 and
are thus similar to humans infected with vCJD.4
BSE infectivity in cattle does not have
widespread tissue distribution.

We report preliminary data from a study
involving blood taken from UK Cheviot sheep
challenged orally with 5 g BSE-affected cattle
brain and transfused into Cheviot sheep from a
scrapie-free flock of New Zealand-derived animals
(MAFF/SF flock). MAFF/SF sheep do not
develop spontaneous TSE and the transfused
animals are housed separately from other sheep.
All sheep in the study have the PrP genotype
AA136QQ171 which has the shortest incubation
period of experimental BSE in sheep.5 19 transfusions from
BSE-challenged sheep have been
done, mostly with whole blood. Sheep have
complex blood groups and only simple
cross-matching can be done by mixing recipient
serum and donor erythrocytes and vice versa.
Therefore single transfusions only were made
between sedated cross-matched animals to
minimise the risk of severe reactions. Negative
controls were MAFF/SF sheep transfused with
blood from uninfected UK Cheviot sheep. As a
positive control, MAFF/SF sheep were
intravenously injected with homogenised BSE-affected
cattle brain.

We have seen BSE clinical signs and pathological
changes in one recipient of blood from a
BSE-infected animal, and we regard this finding
as sufficiently important to report now rather
than after the study is completed, several years
hence. The blood donation resulting in
transmission of BSE to the recipient was 400 mL
of whole blood taken from a healthy sheep
318 days after oral challenge with BSE. BSE subsequently
developed in this donor animal 629
days after challenge, indicating that blood was taken
roughly half way through the incubation
period. 610 days after transfusion, the transfused
sheep (D505) itself developed typical TSE
signs: weight loss, moderate pruritus, trembling
and licking of the lips, hind-limb ataxia, and
proprioceptive abnormalities. This is the first
experimental transmission of BSE from sheep to
sheep and so we have nothing with which to compare
this incubation period directly. In
cross-species transmissions, bovine BSE injected
intracerebrally gives incubation periods of
about 450 days in these sheep,5 and the donor animal
had an oral BSE incubation period of 629
days (see above). There are no similar data
available on other infection routes.
Immunocytochemistry with the antibody BG4 on tissues
taken from sheep D505 showed
widespread PrPSc deposition throughout the brain and
periphery. Western blot analysis of brain
tissue with the antibody 6H4 showed that the PrPSc
protein had a glycoform pattern similar to
that of experimental BSE in sheep and unlike that
of UK natural scrapie (figure), indicating that
the TSE signs resulted from transmission
of the BSE agent. All other recipients of transfusions
and positive and negative controls are
alive and healthy. The positive controls, which involve a
species barrier, are expected to have
lengthy incubation periods. With one exception, all
transfused animals are at earlier stages
post-transfusion than was D505. The exception is a
sheep which is healthy 635 days after transfusion
with BSE-blood donated at less than 30% of
the BSE incubation period of the donor sheep.

PrPSc (proteinase K treated) analysed by SDS-PAGE,
immunoblotted with 6H4, and
visualised with a chemiluminescent substrate

All lanes are from the same gel with different
exposure times. Size markers are to the left of
lane 1. Lane1: natural scrapie sheep brain,
3 min exposure. Lane 2: as lane 1, 10 min exposure.
Lane 3: sheep D505, blood-transfusion
recipient, 10 min exposure. Lane 4: experimental
BSE-affected sheep brain, 30 s exposure.
Lane 5: as lane 4, 10 min exposure. Each lane
loaded with amount of protein extracted from
0·1 g wet weight of brain, except lane 3 which
was extracted from 0·2 g brain.

Although this result was in only one animal, it
indicates that BSE can be transmitted between
individuals of the same species by whole-blood
transfusion. We have no data on blood fractions
or on levels of infectivity in blood of preclinical
vCJD cases, but whole blood is not now used in
UK transfusions. The presence of BSE infectivity
in sheep blood at an early stage in the
incubation period suggests that it should be
possible to identify which cells are infected, to test
the effectiveness of leucodepletion, and to
develop a diagnostic test based on a blood sample.

We thank Karen Brown, Moira Bruce, Calum
McKenzie, David Parnham, Diane Ritchie, and
the Scottish Blood Transfusion Service. The
project is funded by the Department of Health.

1 Bruce ME, Will RG, Ironside JW, et al.
Transmissions to mice indicate that 'new variant' CJD
is caused by the BSE agent. Nature 1997;
389: 488-501 [PubMed].

2 Schmerr MJ, Jenny A, Cutlip RC. Use of
capillary sodium dodecyl sulfate gel electrophoresis
to detect the prion protein extracted from
scrapie-infected sheep. J Chromatogr B Biomed
Appl 1997; 697: 223-29 [PubMed].

3 Foster JD, Bruce M, McConnell I, Chree A,
Fraser H. Detection of BSE infectivity in brain
and spleen of experimentally infected sheep.
Vet Rec 1996; 138: 546-48 [PubMed].

4 Hill AF, Zeidler M, Ironside J, Collinge J.
Diagnosis of new variant Creutzfeldt-Jakob disease
by tonsil biopsy. Lancet 1997; 349: 99-100.

5 Goldmann W, Hunter N, Smith G, Foster J,
Hope J. PrP genotype and agent effects in
scrapie: change in allelic interaction with
different isolates of agent in sheep, a natural host of
scrapie. J Gen Virol 1994; 75: 989-95 [PubMed].

Institute for Animal Health, Compton, Newbury,
UK (F Houston PhD, CJ Bostock
PhD); and Institute for Animal Health, Neuropathogenesis Unit,
Edinburgh, EH9
3JF, UK (N Hunter PhD, JD Foster BSc, Angela Chong BSc)

Correspondence to: Dr N Hunter


Volume 356, Number 9234 16 September 2000




BSE and transmission through blood

Lancet 2000; 356: 955 - 956
Download PDF (55 Kb)
Wether the outbreak of variant Creutzfeldt-Jakob disease
(vCJD) in the UK will ultimately
affect hundreds, or tens of thousands of people,
cannot yet be predicted.1 If large numbers of
apparently healthy people are now silently incubating
infections with bovine spongiform
encephalopathy (BSE), the implications for public
health include the possiblity that blood from
such individuals may be infectious. Established facts
about infectivity in the blood of human
beings and animals with transmissible spongiform
encephalopathies (TSEs) are as follows:2-4

Blood, especially the buffy-coat component,
from animals experimentally infected with
scrapie or CJD and from either a clinical or
preclinical incubation phase, is consistently infectious
when bioassayed by intracerebral or intraperitoneal
inoculation into the same species;

In naturally infected animals (sheep and goats
with scrapie, mink with transmissible mink
encephalopathy, and cows with BSE), all attempts
to transmit disease through the inoculation of
blood have failed;

Blood from four of 37 human beings with
clinically evident sporadic CJD has been reported
to transmit the disease after intracerebral inoculation into guineapigs,
mice, or hamsters. But each
success has been questioned on technical grounds
and has not been reproducible; and

Epidemiological data have not revealed a
single case of CJD that could be attributed to the
administration of blood or blood products among
patients with CJD, or among patients with
haemophilia and other congenital clotting or
immune deficiencies who receive repeated doses of
plasma concentrates.

No comparable information about vCJD is available.
However, since lymphoreticular organs,
such as tonsils have been shown to contain the
prion protein (which is an excellent index of
infectivity), whereas it is not detectable in
patients with sporadic CJD, there is some reason to
worry that blood from individuals incubating
vCJD might be infectious.5 Data from studies into
the ability of blood from experimentally infected
rodents and primates with vCJD to transmit the
disease will not be available for months or years.

In this issue of The Lancet, F Houston and co-workers
report convincing evidence that blood
from a seemingly healthy sheep incubating BSE
(infected by the oral route with brain from a
diseased cow) was able to cause the disease when
transfused into another sheep. This
observation is entirely consistent with past
experience in experimentally infected rodents. It
extends current knowledge about blood infectivity
in experimental models to a host/TSE strain
pair that is closer to the human vCJD situation
than the earlier rodent studies. It is also the first
successful transfusion of BSE from blood taken
during the all-important incubation period of
infection. This result is part of a larger study
(n=19) that includes both positive and negative
control animals, all still healthy and in various
early stages of the incubation period.

Is it appropriate to publish an experimental
result from a single animal in a study that is not far
enough along even to have validated its positive
controls? Especially a result that does not in any
fundamental way change our current thinking about
BSE and vCJD and which would not seem
to have any practical consequences for public
health? The UK National Blood Transfusion
Service has already implemented leucodepletion
of donated blood, and imports all plasma and
plasma derivatives from BSE-free countries. No
further measures would seem possible--short
of a draconian decision to shut down the whole
UK blood-donor system. What, therefore, is the
rationale for this publishing urgency? The
answer, evidently, is a perceived need to "defuse", by
an immediate and accurate scientific report,
public reaction to possibly inaccurate media
accounts. The full study, when it appears, will
be an important addition to our knowledge of
TSEs, but science should not be driven to what
in certain medical quarters might be termed a
premature emission through fear of media misrepresentation.

Paul Brown

Laboratory of Central Nervous System Studies,
National Institutes of Health, Bethesda,
MD 20892, USA

1 Ghani AC, Ferguson NM, Donnelly CA, Anderson RM.
Predicted vCJD mortality in Great
Britain. Nature 2000; 406: 583-84 [PubMed].

2 Brown P. Can Creutzfeldt-Jakob disease be
transmitted by transfusion? Curr Opin Hematol
1995; 2: 472-77 [PubMed].

3 Brown P, Cervenáková L, McShane LM, Barber P,
Rubenstein R, Drohan WN. Further
studies of blood infectivity in an experimental
model of transmissible spongiform encephalopathy,
with an explanation of why blood components do not transmit
Creutzfeldt-Jakob disease in
humans. Transfusion 1999; 39: 1169-78 [PubMed].

4 Rohwer RG. Titer, distribution, and transmissibility
of blood-borne TSE infectivity. Presented
at Cambridge Healthtech Institute 6th Annual Meeting
"Blood Product Safety: TSE, Perception
versus Reality", MacLean, VA, USA, Feb 13-15, 2000.

5 Hill AF, Butterworth RJ, Joiner S, et al. Investigation
of variant Creutzfeldt-Jakob disease and
other human prion diseases with tonsil biopsy samples. Lancet 1999; 353: