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From: TSS ()
Subject: Evidence of scrapie transmission via milk
Date: April 9, 2008 at 2:42 pm PST

Research article
Evidence of scrapie transmission via milk
Timm Konold , S JO Moore , Susan J Bellworthy and Hugh A Simmons

BMC Veterinary Research 2008, 4:14doi:10.1186/1746-6148-4-14


Published: 8 April 2008

Abstract (provisional)
Background
The risk of scrapie infection increases with increased duration and
proximity of contact between sheep at lambing. Scrapie infectivity has not
been detected in milk but cellular prion protein, the precursor of
disease-associated prion protein PrPd, has been found in milk from
ruminants. To determine whether milk is able to transmit scrapie, 18 lambs
with a prion protein genotype associated with high susceptibility to scrapie
(VRQ/VRQ) were fed milk from twelve scrapie-affected ewes of the same
genotype, and 15 VRQ/VRQ sheep reared on scrapie-free dams served as
controls.

Results
Three lambs fed milk from scrapie-affected ewes were culled due to
intercurrent diseases at 43, 44 and 105 days of age respectively, and PrPd
was detected in the distal ileum of the first two lambs, whilst PrPd was not
found in lymphoreticular tissues in the third lamb. A control lamb, housed
in a separate pen and culled at 38 days of age, was also negative for PrPd
in a range of tissues. Samples of recto-anal mucosa associated lymphoid
tissue collected from the remaining 15 live lambs at seven months of age
(between five to seven months after mixing) were positive for PrPd in the
scrapie milk recipients, whereas PrPd was not detected in the remaining 14
controls at that time. A subsequent sample collected from control lambs
revealed PrPd accumulation in two of five lambs eight months after mixing
with scrapie milk recipients suggestive of an early stage of infection via
lateral transmission. By contrast, the control sheep housed in the same
building but not mixed with the scrapie milk recipients were still negative
for PrPd.

Conclusions
The presence of PrPd in distal ileum and rectal mucosa indicates
transmission of scrapie from ewe to lamb via milk (or colostrum) although it
is not yet clear if such cases would go on to develop clinical disease. The
high level of infection in scrapie-milk recipients revealed by rectal
mucosal testing at approximately seven months of age may be enhanced or
supplemented by intra-recipient infection as these lambs were mixed together
after feeding with milk from scrapie-affected ewes and we also observed
lateral transmission from these animals to lambs weaned from scrapie-free
ewes.

http://www.biomedcentral.com/1746-6148/4/14/abstract

full text ;

http://www.biomedcentral.com/content/pdf/1746-6148-4-14.pdf


TSS




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