[show abstract][hide abstract] ABSTRACT: Avian scavengers, such as American crows (Corvus brachyrhynchos), have potential to translocate infectious agents (prions) of transmissible spongiform encephalopathy (TSE) diseases including chronic wasting disease, scrapie, and bovine spongiform encephalopathy. We inoculated mice with fecal extracts obtained from 20 American crows that were force-fed material infected with RML-strain scrapie prions. These mice all evinced severe neurological dysfunction 196-231 d postinoculation ([Formula: see text] = 198; 95% CI: 210-216) and tested positive for prion disease. Our results suggest a large proportion of crows that consume prion-positive tissue are capable of passing infectious prions in their feces ([Formula: see text] = 1.0; 95% CI: 0.8-1.0). Therefore, this common, migratory North American scavenger could play a role in the geographic spread of TSE diseases.
PLoS ONE 01/2012; 7(10):e45774. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Two serine protease enzymes, subtilisin 309 and subtilisin 309-v, were used to digest brain homogenates containing high levels of prion infectivity using mildly alkaline conditions to investigate prion decontamination methods. To establish that PrPres infectivity was eliminated, we utilized the Rocky Mountain Laboratory (RML) mouse-adapted scrapie model system for bioassay. Only one digestion condition (subtilisin 309 at 138 mAU/ml, 55 °C and 14 h digestion time pH 7.9) was considered to be highly relevant statistically (P < 0.001) compared to control, with 52% of challenged mice surviving until the end of the study period. In contrast, treatment of PrPres by autoclaving at 134 °C or treatment with hypochlorite at a concentration of 20,000 ppm completely protected mice from prionosis. Further, in vitro assays suggest that potential proteolytic based PrPres decontamination methods must use high enzyme concentration, pH values >9.0, and elevated temperatures to be a safely efficacious, thereby limiting applicability on delicate surgical instruments and use in the environment.
[show abstract][hide abstract] ABSTRACT: Prion diseases such as bovine spongiform encephalopathy, chronic wasting disease, and scrapie pose serious risks to human and animal health due to a host of disease-specific factors, including the resistance of infectious prions (PrP(Sc)) to natural degradation and to most commercial inactivation procedures. In an attempt to address this concern, a mouse model was used to compare the efficacy of an alkaline hydrolysis process with a simulated continuous-flow rendering treatment for disposal of PrP(Sc)-infected biological material. Female C57/BL6 mice (N = 120) were randomly divided into 4 treatment groups (n = 30), and each mouse was injected intraperitoneally with their designated treatment inoculum. Treatment groups 1 and 2 served as the positive and negative controls, respectively. Group 3 was inoculated with rendered scrapie-positive mouse brain material to investigate the effectiveness of simulated continuous-flow rendering practices to reduce or eliminate PrP(Sc). Group 4 was inoculated with hydrolyzed scrapie-positive mouse brain material to determine the sterilizing effect of alkaline hydrolysis on PrP(Sc). Mice were monitored for overt signs of disease, and those showing clinical signs were killed to prevent undue suffering. Brains were obtained from all mice that died (or were killed) and analyzed with an ELISA for the presence of PrP(Sc). Results indicated that the simulated continuous-flow rendering treatment used for preparing the rendering treatment group inoculum failed to completely eliminate PrP(Sc). Rendering delayed, but did not stop, clinical mouse-adapted scrapie transmission. Compared with positive controls, the rendering treatment group experienced an approximate 45-d average delay in days to death (250 vs. 205 d for positive controls; P < 0.0001) and a death loss of 73.9% (P = 0.0094). Positive controls suffered 100% death loss. The results validated the efficacy of the alkaline hydrolysis treatment to inactivate all PrP(Sc) because no alkaline hydrolysis treatment group mice succumbed to the disease (P < 0.0001). Based on our results, alkaline hydrolysis should be considered by the animal rendering and beef packing industries as an alternative to incineration, landfill burial, and rendering for disposing of biological material potentially infected or contaminated with prion disease.
Journal of Animal Science 12/2008; 87(5):1787-93. · 2.09 Impact Factor