- Submitted to: European Society of Veterinary Pathology
Publication Type: Abstract Publication Acceptance Date: June 5, 2006 Publication
Date: August 31, 2006 Citation: Hamir, A., Kunkle, R., Cutlip, R., Miller,
J., Williams, E., Richt, J. 2006. Transmission of chronic wasting disease
agent of mule deer (CWD**md) to Suffolk sheep by intracerebral route
[abstract]. European Society of Veterinary Pathology 24th Annual Meeting.
Paper No. P63. p. 171-172.
- Technical Abstract: Chronic wasting disease (CWD) is
a transmissible spongiform encephalopathy (TSE) that has been identified
in captive and free-ranging cervids in the U.S. since 1967. To determine
the transmissibility of CWD to sheep, 8 Suffolk lambs [4 QQ and 4 QR at
codon 171 of prion protein (PRNP) gene] were inoculated intracerebrally
with a pooled brain suspension from 28 mule deer naturally affected with
CWD (CWD**md). Two other lambs (1 QQ and 1 QR at codon 171 of the PRNP
gene) were kept as non- inoculated controls. Within 36 months post inoculation
(MPI), 2 animals became sick and were euthanized. Only 1 sheep (euthanized
at 35 MPI) showed clinical signs that were consistent with those described
for scrapie. Microscopic lesions of spongiform encephalopathy (SE) were
only seen in the sheep with the clinical signs of TSE and its tissues
were positive for the abnormal prion protein (PrP**res) by immunohistochemistry
and Western blot. Between 36 and 60 MPI, 3 other sheep were euthanized
because of conditions unrelated to TSE. The remaining 3 sheep remained
non- clinical at the termination of the study (72 MPI) and were euthanized
at that time. One of the 3 animals revealed SE and its tissues were positive
for PrP**res. Both sheep positive for PrP**res were homozygous QQ at codon
171. Retrospective examination of the PRNP genotype of the 2 TSE-positive
animals revealed that the sheep with clinical prion disease (euthanized
at 35 MPI) was heterozygous (AV) and the sheep with the sub-clinical disease
(euthanized at 72 MPI) was homozygous (AA) at codon 136 of the PRNP.
These findings demonstrate that transmission of the CWD**md agent to sheep
via the intracerebral route is possible. Interestingly, the host genotype
may play a significant part in successful transmission and incubation
period of CWD**md.