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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Virus and Prion Research » Research » Publications at this Location » Publication #135909


item Hamir, Amirali
item Miller, Janice

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/6/2002
Publication Date: 8/6/2002
Citation: N/A

Interpretive Summary:

Technical Abstract: At the National Animal Disease Center (NADC), Ames, Iowa, we have initiated studies on the experimental transmission of CWD agent to cattle, sheep, and raccoons. In all 3 experiments the inoculum used was of mule deer origin, and the route of administration was intracerebral. None of the experiments have as yet been completed. These investigations are of long-term duration; therefore, an interim progress report of the 3 studies is warranted. The cattle experiment was started in 1997 and in 2001 we published a preliminary report documenting TSE-like disease in 3 of the 13 inoculated cattle (J Vet Diagn Invest 13:91-96, 2001). Since then 2 other inoculated cattle have been euthanized. Neither of these cattle had lesions in their brains and both were negative for PrP by immunohistochemistry (IHC). At this time, approximately 5 years post inoculation (PI), all remaining cattle are apparently healthy. The sheep experiment was initiated in 1999 with 8 animals, including 4 of each 171 genotype (QQ or QR). Since the start of this experiment, 1 QQ sheep has been euthanized and the brain of this animal was negative for PrP by IHC. At this time, approximately 3 years PI, all remaining sheep are apparently healthy. The raccoon study was begun in 1999. In this investigation, 4 raccoon kits were inoculated. This experiment was part of a larger study to see if raccoons could be used as a model for differentiation of scrapie, TME, and CWD. At this time, 3+ years PI, all raccoons in the CWD-inoculated group are apparently healthy. In addition to the above mentioned CWD experiments, 6 Rocky Mountain elk (Cervus elaphus nelsoni) calves were inoculated intracerebrally with brain suspension from sheep naturally affected with scrapie. One elk developed a brain abscess and was euthanized at 7 weeks PI and 2 others died at 6 and 15 months PI because of coincidental physical injuries. At 25 and 35 months PI, 2 other elk died after brief terminal neurological episodes. Necropsy of these elk revealed moderate weight loss but no other gross lesions. Microscopically, characteristic lesions of spongiform encephalopathy were seen throughout the brains and spinal cords and in both cases these tissues were positive for PrPres by IHC and Western blot, and for scrapie-associated fibrils (SAF) by negative stain electron microscopy. PrPres and SAF were not detected in the 3 elk that died or were euthanized because of coincidental causes. Four years after initiation of this experiment, the 1 remaining inoculated elk and 2 uninoculated (control) elk are alive and apparently healthy. These findings demonstrate that: 1) sheep scrapie agent can be transmitted to elk by intracerebral inoculation; 2) the infection can result in severe, widely distributed spongiform change and accumulations of PrPres and SAF in the CNS; and 3) this condition cannot be distinguished from chronic wasting disease (CWD) with currently available diagnostic techniques.