Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2000
Publication Date: N/A
Citation: Interpretive Summary: Since 1967, a fatal disease of brain called chronic wasting disease (CWD), has been identified in free ranging wild ruminant species in Colorado and Wyoming. CWD has been experimentally transmitted by intra-cranial and oral inoculations of brain tissue from affected animals into a variety of wild and laboratory animal species. Except for one intra-cranial transmission of infection to a goat, CWD agent has not been transmitted to other domestic animals. To test the transmissibility of CWD agent to cattle, 13 calves were inoculated intra-cranially with brain suspension from mule deer naturally infected with CWD. The primary objective of the experiment was to provide information about clinical course and lesions, and to determine the suitability of commonly used diagnostic procedures for diagnosis of CWD in cattle. Data presented here are preliminary observations after 3 years of observation. Between 22 and 27 months after inoculation, 3 animals were efound recumbent and were killed for examination. There was evidence of severe loss of body weight in 2 animals and a large abscess in the lungs was present in the third animal. Microscopic lesions in the brain were subtle in 2 and absent in the third case. However, all were positive for the presence of enzyme resistant prion protein, a specific marker of the disease. A non-inoculated control animal killed during the same time period did not have lesions or the disease marker was not present in its brain. All remaining inoculated cattle are alive and healthy. The impact of this study is that CWD can be transmitted to domestic cattle and that the surveillance methods currently used for diagnosis of CWD in cattle are valid.
Technical Abstract: To determine the clinical signs, nature of lesions, and comparison to natural bovine spongiform encephalopathy (BSE) and experimental scrapie in cattle, calves were inoculated intracerebrally with brain suspension from mule deer naturally affected with CWD. Between 24 and 27 months post inoculation, 3 animals became recumbent and were euthanized. Gross necropsies revealed emaciation in 2 animals and presence of a large chroni pulmonary abscess in the third. Brains were examined for protease-resistant prion protein (PrPres) by immunohistochemistry and Western blotting, and for scrapie associated fibrils (SAF) by negative stain electronmicroscopy. Microscopic lesions in the brain were subtle in 2 animals and absent in the third case. However, all 3 animals were positive for PrPres by immunohistochemistry and Western blot, and SAF were detected in 2 of the animals. A non-inoculated control animal euthanized during the same time- period did not have PrPres in its brain. These are preliminary observation from a currently in-progress experiment. Three years after the CWD challenge, the 10 remaining inoculated cattle are alive and apparently healthy. These preliminary findings demonstrate that diagnostic techniques currently used for BSE surveillance would also detect CWD in cattle should it occur naturally.