Greenlee Justin J, Nicholson Eric M, Smith Jodi D, Kunkle Robert A, Hamir Amir N
Virus and Prion Research Unit, National Animal Disease Center, U.S. Department of Agriculture, Agricultural Research Service, Ames, IA, USA.
J Vet Diagn Invest. 2012 Nov;24(6):1087-93. doi: 10.1177/1040638712461249. Epub 2012 Sep 18.
Cattle could be exposed to the agent of chronic wasting disease (CWD) through contact with infected farmed or free-ranging cervids or exposure to contaminated premises. The purpose of the current study was to assess the potential for CWD derived from elk to transmit to cattle after intracranial inoculation. Calves (n = 14) were inoculated with brain homogenate derived from elk with CWD to determine the potential for transmission and to define the clinicopathologic features of disease. Cattle were necropsied if clinical signs occurred or at the end of the study (49 months postinoculation; MPI). Clinical signs of poor appetite, weight loss, circling, and bruxism occurred in 2 cattle (14%) at 16 and 17 MPI, respectively. Accumulation of abnormal prion protein (PrP(Sc)) occurred in only the 2 clinically affected cattle and was confined to the central nervous system, with the most prominent immunoreactivity in midbrain, brainstem, and hippocampus with lesser immunoreactivity in the cervical spinal cord. The rate of transmission was lower than in cattle inoculated with CWD derived from mule deer (38%) or white-tailed deer (86%). Additional studies are required to fully assess the potential for cattle to develop CWD through a more natural route of exposure, but a low rate of transmission after intracranial inoculation suggests that risk of transmission through other routes is low. A critical finding is that if CWD did transmit to exposed cattle, currently used diagnostic techniques would detect and differentiate it from other prion diseases in cattle based on absence of spongiform change, distinct pattern of PrP(Sc) deposition, and unique molecular profile.
牛可能通过接触感染的养殖或自由放养的鹿科动物或暴露于受污染的场所而接触慢性消耗性疾病（CWD）病原体。本研究的目的是评估颅内接种后源自麋鹿的CWD传播给牛的可能性。给14头犊牛接种来自患有CWD的麋鹿的脑匀浆，以确定传播的可能性并确定疾病的临床病理特征。如果出现临床症状或在研究结束时（接种后49个月；MPI）对牛进行尸检。分别在16和17 MPI时，2头牛（14%）出现食欲减退、体重减轻、转圈和磨牙等临床症状。仅在2头临床受影响的牛中出现异常朊病毒蛋白（PrP(Sc)）积累，并局限于中枢神经系统，中脑、脑干和海马体的免疫反应最为明显，颈脊髓的免疫反应较弱。传播率低于接种来自骡鹿（38%）或白尾鹿（86%）的CWD的牛。需要进一步研究以全面评估牛通过更自然的暴露途径感染CWD的可能性，但颅内接种后的低传播率表明通过其他途径传播的风险较低。一个关键发现是，如果CWD确实传播给了暴露的牛，目前使用的诊断技术将基于不存在海绵状变化、PrP(Sc)沉积的独特模式和独特的分子谱检测并将其与牛的其他朊病毒疾病区分开来。
