Submitted to: Veterinary Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/20/2007
Publication Date: 7/1/2007
Citation: Hamir, A.N., Miller, J.M., Kunkle, R.A., Hall, S.M., Richt, J.A. 2007. Susceptibility of cattle to first-passage intracerebral inoculation with chronic wasting disease agent from white-tailed deer. Veterinary Pathology. 44:487-493. Interpretive Summary: This study reports findings assessing susceptibility of cattle to infection following direct surgical inoculation of the transmissible spongiform encephalopathy (TSE), chronic wasting disease (CWD, from white tailed deer) into the brain of 14 cattle. Three-month-old calves were inoculated with the CWD agent from white tailed deer. Two non-inoculated calves served as controls. Within 26 months post inoculation, 12 inoculated animals had lost weight, revealed abnormal clinical signs, and were euthanatized. Laboratory tests revealed the presence of a unique pattern of the disease agent in tissues of these animals. These findings demonstrate that when CWD is directly inoculated into the brain of cattle, 86% of inoculated cattle develop clinical signs of the disease. The findings also indicate that diagnostic techniques currently used for detection of bovine spongiform encephalopathy (BSE) would detect CWD in cattle should it ever cross the species barrier. Moreover, these findings confirm our earlier findings with CWD from mule deer, thus demonstrating a unique pattern of the CWD disease agent from deer when experimentally inoculated into cattle, further validating our ability to distinguish this form of cross-species TSE transmission from BSE in cattle.
Technical Abstract: To compare clinicopathological findings of chronic wasting disease (CWD) from white-tailed deer (CWD**wtd) with other transmissible spongiform encephalopathies [transmissible spongiform encephalopathy (TSE), prion diseases) that have been shown to be experimentally transmissible to cattle [sheep scrapie, CWD of mule deer (CWD**md) and transmissible mink encephalopathy (TME)], 14 three-month-old calves were intracerebrally inoculated with the CWD**wtd agent. Two uninoculated calves served as controls. Within 26 months post inoculation (MPI), 12 inoculated animals had lost considerable weight and eventually became recumbent. Eleven of these had clinical signs of central nervous system (CNS) abnormality and all 12 were euthanized. Although microscopic lesions of spongiform encephalopathy (SE) were not seen in CNS tissues, PrP**res was detected by immunohistochemistry (IHC) and Western blot (WB). These findings demonstrate that when CWD**wtd is intracerebrally inoculated in cattle, 86% of inoculated cattle develop abnormal clinical signs and amplify PrP**res in their CNS tissues without evidence of morphologic lesions of SE. The latter has also been shown with other TSE agents (scrapie and CWD**md) similarly inoculated into cattle. These findings suggest that the diagnostic techniques currently used for confirmation of bovine spongiform encephalopathy (BSE) would detect CWD**wtd in cattle should it occur naturally. The absence of microscopic morphologic lesions and a unique IHC pattern of CWD**wtd in cattle, suggests that it should be possible to distinguish this form of cross-species transmission from BSE in cattle.