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Subject: Experimental Second Passage of CWD (CWDmule deer) Agent to Cattle
Date: April 25, 2006 at 8:01 am PST

Experimental Second Passage of Chronic Wasting

Disease (CWDmule deer) Agent to Cattle


A. N. Hamir, R. A. Kunkle, J. M. Miller, J. J. Greenlee and J. A. Richt

Agricultural Research Service, United States Department of Agriculture, National Animal Disease Center, 2300 Dayton

Avenue, P.O. Box 70, Ames, IA 50010, USA

Summary

To compare clinicopathological findings in first and second passage chronic wasting disease (CWDmule deer)

in cattle, six calves were inoculated intracerebrally with brain tissue derived froma first-passageCWD-affected

calf in an earlier experiment. Two uninoculated calves served as controls. The inoculated animals began to

lose both appetite and weight 10–12 months later, and five subsequently developed clinical signs of central

nervous system (CNS) abnormality. By 16.5 months, all cattle had been subjected to euthanasia because of

poor prognosis. None of the animals showed microscopical lesions of spongiform encephalopathy (SE) but

PrPres was detected in their CNS tissues by immunohistochemistry (IHC) and rapid Western blot (WB)

techniques. Thus, intracerebrally inoculated cattle not only amplified CWD PrPres from mule deer but also

developed clinicalCNSsigns in the absence of SElesions.This situation has also been shown to occur in cattle

inoculated with the scrapie agent. The study confirmed that the diagnostic techniques currently used for

diagnosis of bovine spongiformencephalopathy (BSE) in theUS would detect CWDin cattle, should it occur

naturally. Furthermore, it raised the possibility of distinguishing CWDfromBSE in cattle, due to the absence

of neuropathological lesions and to a distinctive multifocal distribution of PrPres, as demonstrated by IHC

which, in this study, appeared to be more sensitive than the WB technique.



snip...



The present study and a previous experiment

(Hamir et al., 2005a) have established the biological

characteristics of the CWDmule deer agent in cattle.

However, isolates of CWD from other cervids (e.g.

CWDwhite-tailed and CWDelk) may differ. Transmission

experiments with different CWD isolates

are therefore needed to examine the possibility of

variation in the CWD agent in wild cervids. Such

experiments have recently been initiated at the

National Animal Disease Center (NADC).


Acknowledgments

We thank Dr Katherine I. O’Rourke for providing

the antibody for the IHC procedure. Martha

Church, Kevin Hassall, Dennis Orcutt, Jean

Donald, Sharla Van Roekel, and animal handlers

at the NADC provided expert technical assistance.

This study was carried out under the guidelines of

the institutional Animal Care and Use committee at

NADC. Mention of trade names or commercial

products in this article is solely for the purpose of

providing specific information and does not imply

recommendation or endorsement by the United

States Department of Agriculture.

References.......snip........end..............TSS
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