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From: TSS ()
Date: April 12, 2008 at 7:31 pm PST

In Reply to: Evidence of scrapie transmission via milk posted by TSS on April 9, 2008 at 2:42 pm:



a non-profit Swiss Foundation

(April 11, 2008)


With regards to:-

Konold et al.: Evidence of scrapie transmission via milk, BMC Veterinary
Research 2008, 4:14;
doi:10.1186/1746-6148-4-14; Published 8 April 2008; Available at:-

TAFS welcomes publication of these findings. They contribute to the
understanding of the
mechanisms of transmission of scrapie as a prion disease of sheep and goats
that has been known for
over 200 years.

Scrapie is not a highly contagious disease. It does not spread easily, but
it is difficult to eradicate. It is
known to spread between sheep, both from ewe to lamb and to other unrelated
sheep and goats. The
exact route of transmission has not been determined so far. There are
several possible routes, which
include contact with placenta of infected ewes, or possibly before birth
while the lamb is still in the
womb. Transmission via milk and/or uterine fluids after birth are additional
The study being reported attempted to assess the scope for transmission,
under a worst-case scenario,
by collecting milk from sheep of highly susceptible genetic makeup (high
risk group), at a time when
they were either about to die of scrapie, or when the first clinical signs
were seen. Their milk was
collected and fed to lambs that were born to uninfected mothers and kept in
isolation while they
received the milk. These lambs were also of the most susceptible genotype
The lambs have been shown to be infected by the testing of tissue samples
collected either while still
alive, by biopsy, or from some that had died of other diseases. None have
yet reached the point of
clinical disease themselves, and infectivity itself has not been
demonstrated. Tests have revealed the
presence of abnormal prion protein (PrPSc) that is normally recognised as a
marker for the presence of

The success of the study was dependent on having scrapie-free lambs to
receive the milk. Despite
having fully susceptible ewes and susceptible lambs, the ease with which the
lambs were infected is a
surprise. The experimental design anticipated transmission to smaller
numbers of lambs. For this
reason lambs received both milk and colostrum (the milk produced within the
first 24-48 hours after
lambing) from the same ewe in order to maximise the likelihood of
transmission. As a result, it is not
possible to conclude at this point whether transmission occurred via
colostrum, milk or both. The
study will therefore now be repeated, feeding lambs only on colostrum or

This is important for several reasons.

? Firstly, colostrum would not be used for human consumption.

? Secondly, colostrum is rich in protein and antibodies that help to protect
the lamb in the early
days of life before its own immune system is fully functional. For that
reason farmers
sometimes collect and freeze colostrum to feed to other lambs, sometimes
pooling it to feed to
several lambs. This practice could increase the potential for infection of
lambs at their most
vulnerable time of life.

Scrapie is not recognised as a risk to humans, ***although this cannot be
ruled out with certainty .The risk
to humans from scrapie, and the scientific uncertainties that underpin any
statement on risk, have been
discussed at length in the two EFSA Opinions cited below. Since there is no
established evidence to
date that scrapie poses a risk to human health, the finding that it is
transmissible from sheep to lambs
via milk does not give any reason to change our view that ovine and caprine
milk are safe for human

These results do not at the moment have any direct implications with respect
to the risk from BSE in
milk from cattle. Although an equivalent study has not been conducted in
cattle, other studies
attempting to find infectivity in bovine milk have not succeeded. Proving
the total absence of
infectivity is extremely difficult. The evidence for the absence of natural
spread of BSE between
cattle, from cow to calf or between unrelated cattle does however suggest
that even in natural
equivalent of this experiment, the feeding of calves on cows? milk,
transmission has not occurred, or
does so only rarely. Consequently, cows? milk is unlikely to carry BSE
infectivity that might put
consumers at risk. Furthermore, the control measures that have been put in
place to eradicate BSE, and
protect consumers in the interim, are succeeding in reducing numbers of
infected cattle year by year.
In conclusion, the study helps to better understand the epidemiology of
scrapie, and may provide an
impetus for additional measures to further strengthen animal or public
health protections in regard to
small ruminants TSEs. However, it does not put in question the safety of
products derived from bovine
milk destined for human consumption.


EFSA (2007). Opinion of the Scientific Panel on Biological Hazards on
certain aspects related to
the risk of Transmissible Spongiform Encephalopathies (TSEs) in ovine and
caprine animals. 8
March 2007. The EFSA Journal. 466:1-10. Available at:-
EFSA (2008). Scientific and technical clarification in the interpretation
and consideration of some
facets of the conclusions of its Opinion of 8 March 2007 on certain aspects
related to the risk of
Transmissible Spongiform Encephalopathies (TSEs) in ovine and caprine
animals. The EFSA
Journal. 626:1-11. Available at:-

1 TAFS is an international platform created by a group of scientists, food
industry experts, animal health regulators, epidemiologists,
diagnosticians, food producers, and consumers. Its purpose is to establish
and maintain lines of communication for the dissemination of
reliable information to the public that can maintain confidence in the
safety of food with regard to Transmissible Animal Diseases.

Saturday, April 12, 2008
Evidence of scrapie transmission via milk

Research articleS

Saturday, April 12, 2008

The sheep industry's scrapie eradication efforts. American Sheep
Nor98-Like Scrapie Found in the United States


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