1
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Patients with isolated REM-sleep behavior disorder have elevated levels of alpha-synuclein aggregates in stool. NPJ Parkinsons Dis 2023; 9:14. [PMID: 36732520 PMCID: PMC9895074 DOI: 10.1038/s41531-023-00458-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 01/16/2023] [Indexed: 02/04/2023] Open
Abstract
Misfolded and aggregated α-synuclein is a neuropathological hallmark of Parkinson's disease (PD). Thus, α-synuclein aggregates are regarded as a biomarker for the development of diagnostic assays. Quantification of α-synuclein aggregates in body fluids is challenging, and requires highly sensitive and specific assays. Recent studies suggest that α-synuclein aggregates may be shed into stool. We used surface-based fluorescence intensity distribution analysis (sFIDA) to detect and quantify single particles of α-synuclein aggregates in stool of 94 PD patients, 72 isolated rapid eye movement sleep behavior disorder (iRBD) patients, and 51 healthy controls. We measured significantly elevated concentrations of α-synuclein aggregates in stool of iRBD patients versus those of controls (p = 0.024) or PD patients (p < 0.001). Our results show that α-synuclein aggregates are excreted in stool and can be measured using the sFIDA assay, which could support the diagnosis of prodromal synucleinopathies.
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2
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Harm TA, Smith JD, Cassmann ED, Greenlee JJ. Combinatorial treatment of brain samples from sheep with scrapie using sodium percarbonate, sodium dodecyl sulfate, and proteinase K increases survival time in inoculated susceptible sheep. Res Vet Sci 2022; 152:497-503. [PMID: 36162234 DOI: 10.1016/j.rvsc.2022.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 08/11/2022] [Accepted: 09/02/2022] [Indexed: 10/14/2022]
Abstract
The agent of scrapie is resistant to most chemical and physical methods of inactivation. Prions bind to soils, metals, and various materials and persist in the environment confounding the control of prion diseases. Most methods of prion inactivation require severe conditions such as prolong exposure to sodium hypochlorite or autoclaving, which may not be suitable for field conditions. We evaluated the efficacy of a combinatorial approach to inactivation of US scrapie strain x124 under the mild conditions of treating scrapie-affected brain homogenate with sodium percarbonate (SPC), sodium dodecyl sulfate (SDS), or in combination followed by proteinase K (PK) digestion at room temperature. Western blot analysis of treated brain homogenate demonstrates partial reduction in PrPSc immunoreactivity. Genetically susceptible VRQ/ARQ Suffolk sheep were oronasally inoculated with 1 g of SPC (n = 1), SDS (n = 2), SDS + PK (n = 2), and SPC + SDS + PK (n = 4) treated brain homogenate. Sheep were assessed daily for clinical signs, euthanized at the development of clinical disease, and tissues were assessed for accumulation of PrPSc. Scrapie status in all sheep was determined by western blot, enzyme immunoassay, and immunohistochemistry. Mean incubation periods (IPs) for SPC (11.9 months, 0% survival), SDS (12.6 months, 0% survival), SDS + PK (14.0 months, 0% survival), and SPC + SDS + PK (12.5 months, 25% survival) were increased compared to positive control sheep (n = 2, 10.7 months, 0% survival) by 1.2, 1.9, 3.3, and 1.8 months, respectively. Treatment did not influence PrPSc accumulation and distribution at the clinical stage of disease. Differences in mean IPs and survival indicates partial but not complete reduction in scrapie infectivity.
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Affiliation(s)
- Tyler A Harm
- Virus and Prion Research Unit, National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, IA, United States of America
| | - Jodi D Smith
- Department of Veterinary Pathology, Iowa State University, Ames, IA, United States of America
| | - Eric D Cassmann
- Virus and Prion Research Unit, National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, IA, United States of America
| | - Justin J Greenlee
- Virus and Prion Research Unit, National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, IA, United States of America.
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3
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Gallardo MJ, Delgado FO. Animal prion diseases: A review of intraspecies transmission. Open Vet J 2021; 11:707-723. [PMID: 35070868 PMCID: PMC8770171 DOI: 10.5455/ovj.2021.v11.i4.23] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 11/16/2021] [Indexed: 11/13/2022] Open
Abstract
Animal prion diseases are a group of neurodegenerative, transmissible, and fatal disorders that affect several animal species. The causative agent, prion, is a misfolded isoform of normal cellular prion protein, which is found in cells with higher concentration in the central nervous system. This review explored the sources of infection and different natural transmission routes of animal prion diseases in susceptible populations. Chronic wasting disease in cervids and scrapie in small ruminants are prion diseases capable of maintaining themselves in susceptible populations through horizontal and vertical transmission. The other prion animal diseases can only be transmitted through food contaminated with prions. Bovine spongiform encephalopathy (BSE) is the only animal prion disease considered zoonotic. However, due to its inability to transmit within a population, it could be controlled. The emergence of atypical cases of scrapie and BSE, even the recent report of prion disease in camels, demonstrates the importance of understanding the transmission routes of prion diseases to take measures to control them and to assess the risks to human and animal health.
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Affiliation(s)
- Mauro Julián Gallardo
- Instituto de Patobiología Veterinaria, IPVet, UEDD INTA-CONICET, Hurlingham, Argentina
- Cátedra de Enfermedades Infecciosas, Facultad de Ciencias Veterinarias, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Fernando Oscar Delgado
- Instituto de Patobiología Veterinaria, IPVet, UEDD INTA-CONICET, Hurlingham, Argentina
- Facultad de Cs. Agrarias y Veterinarias, Universidad del Salvador, Pilar, Argentina
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4
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BSE can propagate in sheep co-infected or pre-infected with scrapie. Sci Rep 2021; 11:11931. [PMID: 34099797 PMCID: PMC8184847 DOI: 10.1038/s41598-021-91397-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 05/24/2021] [Indexed: 11/29/2022] Open
Abstract
To understand the possible role of mixed-prion infections in disease presentation, the current study reports the co-infection of sheep with bovine spongiform encephalopathy (BSE) and scrapie. The bovine BSE agent was inoculated subcutaneously into sheep with ARQ/ARQ or VRQ/ARQ PRNP genotypes either at the same time as subcutaneous challenge with scrapie, or three months later. In addition, VRQ/VRQ sheep naturally infected with scrapie after being born into a scrapie-affected flock were challenged subcutaneously with BSE at eight or twenty one months-of-age. Sheep were analysed by incubation period/attack rate, and western blot of brain tissue determined the presence of BSE or scrapie-like PrPSc. Serial protein misfolding cyclic amplification (sPMCA) that can detect very low levels of BSE in the presence of an excess of scrapie agent was also applied to brain and lymphoreticular tissue. For VRQ/ARQ sheep challenged with mixed infections, scrapie-like incubation periods were produced, and no BSE agent was detected. However, whilst ARQ/ARQ sheep developed disease with BSE-like incubation periods, some animals had a dominant scrapie western blot phenotype in brain, but BSE was detected in these sheep by sPMCA. In addition, VRQ/VRQ animals challenged with BSE after natural exposure to scrapie had scrapie-like incubation periods and dominant scrapie PrPSc in brain, but one sheep had BSE detectable by sPMCA in the brain. Overall, the study demonstrates for the first time that for scrapie/BSE mixed infections, VRQ/ARQ sheep with experimental scrapie did not propagate BSE but VRQ/VRQ sheep with natural scrapie could propagate low levels of BSE, and whilst BSE readily propagated in ARQ/ARQ sheep it was not always the dominant PrPSc strain in brain tissue. Indeed, for several animals, a dominant scrapie biochemical phenotype in brain did not preclude the presence of BSE prion.
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5
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Classical and Atypical Scrapie in Sheep and Goats. Review on the Etiology, Genetic Factors, Pathogenesis, Diagnosis, and Control Measures of Both Diseases. Animals (Basel) 2021; 11:ani11030691. [PMID: 33806658 PMCID: PMC7999988 DOI: 10.3390/ani11030691] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 02/23/2021] [Accepted: 02/25/2021] [Indexed: 12/31/2022] Open
Abstract
Prion diseases, such as scrapie, are neurodegenerative diseases with a fatal outcome, caused by a conformational change of the cellular prion protein (PrPC), originating with the pathogenic form (PrPSc). Classical scrapie in small ruminants is the paradigm of prion diseases, as it was the first transmissible spongiform encephalopathy (TSE) described and is the most studied. It is necessary to understand the etiological properties, the relevance of the transmission pathways, the infectivity of the tissues, and how we can improve the detection of the prion protein to encourage detection of the disease. The aim of this review is to perform an overview of classical and atypical scrapie disease in sheep and goats, detailing those special issues of the disease, such as genetic factors, diagnostic procedures, and surveillance approaches carried out in the European Union with the objective of controlling the dissemination of scrapie disease.
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6
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Abstract
In sheep, scrapie is a fatal neurologic disease that is caused by a misfolded protein called a prion (designated PrPSc). The normal cellular prion protein (PrPC) is encoded by an endogenous gene, PRNP, that is present in high concentrations within the CNS. Although a broad range of functions has been described for PrPC, its entire range of functions has yet to be fully elucidated. Accumulation of PrPSc results in neurodegeneration. The PRNP gene has several naturally occurring polymorphisms, and there is a strong correlation between scrapie susceptibility and PRNP genotype. The cornerstone of scrapie eradication programs is the selection of scrapie-resistant genotypes to eliminate classical scrapie. Transmission of classical scrapie in sheep occurs during the prenatal and periparturient periods when lambs are highly susceptible. Initially, the scrapie agent is disseminated throughout the lymphoid system and into the CNS. Shedding of the scrapie agent occurs before the onset of clinical signs. In contrast to classical scrapie, atypical scrapie is believed to be a spontaneous disease that occurs in isolated instances in older animals within a flock. The agent that causes atypical scrapie is not considered to be naturally transmissible. Transmission of the scrapie agent to species other than sheep, including deer, has been experimentally demonstrated as has the transmission of nonscrapie prion agents to sheep. The purpose of this review is to outline the current methods for diagnosing scrapie in sheep and the techniques used for studying the pathogenesis and host range of the scrapie agent. Also discussed is the US scrapie eradication program including recent updates.
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7
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Detection of Pathognomonic Biomarker PrP Sc and the Contribution of Cell Free-Amplification Techniques to the Diagnosis of Prion Diseases. Biomolecules 2020; 10:biom10030469. [PMID: 32204429 PMCID: PMC7175149 DOI: 10.3390/biom10030469] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 03/16/2020] [Accepted: 03/17/2020] [Indexed: 02/07/2023] Open
Abstract
Transmissible spongiform encephalopathies or prion diseases are rapidly progressive neurodegenerative diseases, the clinical manifestation of which can resemble other promptly evolving neurological maladies. Therefore, the unequivocal ante-mortem diagnosis is highly challenging and was only possible by histopathological and immunohistochemical analysis of the brain at necropsy. Although surrogate biomarkers of neurological damage have become invaluable to complement clinical data and provide more accurate diagnostics at early stages, other neurodegenerative diseases show similar alterations hindering the differential diagnosis. To solve that, the detection of the pathognomonic biomarker of disease, PrPSc, the aberrantly folded isoform of the prion protein, could be used. However, the amounts in easily accessible tissues or body fluids at pre-clinical or early clinical stages are extremely low for the standard detection methods. The solution comes from the recent development of in vitro prion propagation techniques, such as Protein Misfolding Cyclic Amplification (PMCA) and Real Time-Quaking Induced Conversion (RT-QuIC), which have been already applied to detect minute amounts of PrPSc in different matrixes and make early diagnosis of prion diseases feasible in a near future. Herein, the most relevant tissues and body fluids in which PrPSc has been detected in animals and humans are being reviewed, especially those in which cell-free prion propagation systems have been used with diagnostic purposes.
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8
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Tennant JM, Li M, Henderson DM, Tyer ML, Denkers ND, Haley NJ, Mathiason CK, Hoover EA. Shedding and stability of CWD prion seeding activity in cervid feces. PLoS One 2020; 15:e0227094. [PMID: 32126066 PMCID: PMC7053746 DOI: 10.1371/journal.pone.0227094] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Accepted: 12/12/2019] [Indexed: 01/12/2023] Open
Abstract
CWD is an emergent prion disease that now affects cervid species on three continents. CWD is efficiently spread in wild and captive populations, likely through both direct animal contact and environmental contamination. Here, by longitudinally assaying in feces of CWD-exposed white-tailed deer by RT-QuIC, we demonstrate fecal shedding of prion seeding activity months before onset of clinical symptoms and continuing throughout the disease course. We also examine the impact of simulated environmental conditions such as repeated freeze-thaw cycles and desiccation on fecal prion seeding activity. We found that while multiple (n = 7) freeze-thaw cycles substantially decreased fecal seeding activity, desiccation had little to no effect on seeding activity. Finally, we examined whether RT-QuIC testing of landscape fecal deposits could distinguish two premises with substantial known CWD prevalence from one in which no CWD-infected animals had been detected. In the above pilot study, this distinction was possible. We conclude that fecal shedding of CWD prions occurs over much of the disease course, that environmental factors influence prion seeding activity, and that it is feasible to detect fecal prion contamination using RT-QuIC.
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Affiliation(s)
- Joanne M. Tennant
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
| | - Manci Li
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
| | - Davin M. Henderson
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
| | - Margaret L. Tyer
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
| | - Nathaniel D. Denkers
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
| | - Nicholas J. Haley
- Midwestern University, College of Graduate Studies, Glendale, AZ, United States of America
| | - Candace K. Mathiason
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
| | - Edward A. Hoover
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
- * E-mail:
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9
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Haley N, Donner R, Henderson D, Tennant J, Hoover E, Manca M, Caughey B, Kondru N, Manne S, Kanthasamay A, Hannaoui S, Chang S, Gilch S, Smiley S, Mitchell G, Lehmkuhl A, Thomsen B. Cross-validation of the RT-QuIC assay for the antemortem detection of chronic wasting disease in elk. Prion 2020; 14:47-55. [PMID: 31973662 PMCID: PMC6984646 DOI: 10.1080/19336896.2020.1716657] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Chronic wasting disease is a progressively fatal, horizontally transmissible prion disease affecting several members of the cervid species. Conventional diagnosis relies on ELISA or IHC evaluation using tissues collected post-mortem; however, recent research has focused on newly developed amplification techniques using samples collected antemortem. The present study sought to cross-validate the real-time quaking-induced conversion assay (RT-QuIC) evaluation of rectal biopsies collected from an elk herd with endemic CWD, assessing both binary positive/negative test results as well as relative rates of amplification between laboratories. We found that results were correlative in both categories across all laboratories performing RT-QuIC, as well as to conventional IHC performed at a national reference laboratory. A significantly higher number of positive samples were identified using RT-QuIC, with results seemingly unhindered by low follicle counts. These findings support the continued development and implementation of amplification assays in the diagnosis of prion diseases of veterinary importance, targeting not just antemortem sampling strategies, but post-mortem testing approaches as well.
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Affiliation(s)
- N.J. Haley
- Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Glendale, AZ, USA,CONTACT N.J. Haley Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Glendale, AZ, USA
| | - R. Donner
- Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Glendale, AZ, USA
| | - D.M. Henderson
- Prion Research Center, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - J. Tennant
- Prion Research Center, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - E.A. Hoover
- Prion Research Center, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - M. Manca
- TSE/Prion Biochemistry Section, Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, Hamilton, MT, USA
| | - B. Caughey
- TSE/Prion Biochemistry Section, Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, Hamilton, MT, USA
| | - N. Kondru
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
| | - S. Manne
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
| | - A. Kanthasamay
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
| | - S. Hannaoui
- Calgary Prion Research Unit, University of Calgary, Calgary, Alberta, Canada,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada,Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada
| | - S.C. Chang
- Calgary Prion Research Unit, University of Calgary, Calgary, Alberta, Canada,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada,Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada
| | - S. Gilch
- Calgary Prion Research Unit, University of Calgary, Calgary, Alberta, Canada,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada,Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada
| | - S. Smiley
- National and OIE Reference Laboratory for Scrapie and CWD, Canadian Food Inspection, Agency, Ottawa Laboratory-Fallowfield, Ottawa, Ontario, Canada
| | - G. Mitchell
- National and OIE Reference Laboratory for Scrapie and CWD, Canadian Food Inspection, Agency, Ottawa Laboratory-Fallowfield, Ottawa, Ontario, Canada
| | - A.D. Lehmkuhl
- United States Department of Agriculture, APHIS, VS, National Veterinary Services Laboratories, Ames, IA, USA
| | - B.V. Thomsen
- United States Department of Agriculture, APHIS, VS, National Veterinary Services Laboratories, Ames, IA, USA,United States Department of Agriculture, APHIS, VS, Center for Veterinary Biologics, Ames, IA, USA
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10
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Gough KC, Baker CA, Hawkins S, Simmons H, Konold T, Maddison BC. Rapid recontamination of a farm building occurs after attempted prion removal. Vet Rec 2019; 184:97. [DOI: 10.1136/vr.105054] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 09/25/2018] [Accepted: 11/23/2018] [Indexed: 11/03/2022]
Affiliation(s)
| | - Claire Alison Baker
- ADAS, School of Veterinary Medicine and Science, The University of Nottingham; Loughborough UK
| | - Steve Hawkins
- Animal Sciences Unit, Pathology Department; Animal & Plant Health Agency Weybridge; New Haw, Addlestone Surrey UK
| | - Hugh Simmons
- Animal Sciences Unit, Pathology Department; Animal & Plant Health Agency Weybridge; New Haw, Addlestone Surrey UK
| | - Timm Konold
- Animal Sciences Unit, Pathology Department; Animal & Plant Health Agency Weybridge; New Haw, Addlestone Surrey UK
| | - Ben Charles Maddison
- ADAS, School of Veterinary Medicine and Science, The University of Nottingham; Loughborough UK
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11
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Plummer IH, Johnson CJ, Chesney AR, Pedersen JA, Samuel MD. Mineral licks as environmental reservoirs of chronic wasting disease prions. PLoS One 2018; 13:e0196745. [PMID: 29719000 PMCID: PMC5931637 DOI: 10.1371/journal.pone.0196745] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 04/18/2018] [Indexed: 12/26/2022] Open
Abstract
Chronic wasting disease (CWD) is a fatal neurodegenerative disease of deer, elk, moose, and reindeer (cervids) caused by misfolded prion proteins. The disease has been reported across North America and recently discovered in northern Europe. Transmission of CWD in wild cervid populations can occur through environmental routes, but limited ability to detect prions in environmental samples has prevented the identification of potential transmission "hot spots". We establish widespread CWD prion contamination of mineral licks used by free-ranging cervids in an enzootic area in Wisconsin, USA. We show mineral licks can serve as reservoirs of CWD prions and thus facilitate disease transmission. Furthermore, mineral licks attract livestock and other wildlife that also obtain mineral nutrients via soil and water consumption. Exposure to CWD prions at mineral licks provides potential for cross-species transmission to wildlife, domestic animals, and humans. Managing deer use of mineral licks warrants further consideration to help control outbreaks of CWD.
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Affiliation(s)
- Ian H. Plummer
- Department of Forest & Wildlife Ecology, University of Wisconsin – Madison, Madison, Wisconsin, United States of America
| | - Chad J. Johnson
- Departments of Soil Science, Chemistry, and Civil & Environmental Engineering, University of Wisconsin – Madison, Madison, Wisconsin, United States of America
| | - Alexandra R. Chesney
- Molecular and Environmental Toxicology Center, University of Wisconsin – Madison, Madison, Wisconsin, United States of America
| | - Joel A. Pedersen
- Departments of Soil Science, Chemistry, and Civil & Environmental Engineering, Molecular and Environmental Toxicology Center, University of Wisconsin – Madison, Madison, Wisconsin, United States of America
- * E-mail: (MDS); (JAP)
| | - Michael D. Samuel
- Department of Forest & Wildlife Ecology, University of Wisconsin – Madison, Madison, Wisconsin, United States of America
- * E-mail: (MDS); (JAP)
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12
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An in vitro model for assessing effective scrapie decontamination. Vet Microbiol 2017; 207:138-142. [DOI: 10.1016/j.vetmic.2017.05.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 05/10/2017] [Accepted: 05/20/2017] [Indexed: 11/17/2022]
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13
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Plummer IH, Wright SD, Johnson CJ, Pedersen JA, Samuel MD. Temporal patterns of chronic wasting disease prion excretion in three cervid species. J Gen Virol 2017; 98:1932-1942. [PMID: 28708047 DOI: 10.1099/jgv.0.000845] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Chronic wasting disease (CWD) is the only naturally occurring transmissible spongiform encephalopathy affecting free-ranging wildlife populations. Transmission of CWD occurs by direct contact or through contaminated environments; however, little is known about the temporal patterns of CWD prion excretion and shedding in wild cervids. We tested the urine and faeces of three species of captive cervids (elk, mule and white-tailed deer) at 6, 12, 18 and 24 months after oral inoculation to evaluate the temporal, species- and genotype-specific factors affecting the excretion of CWD prions. Although none of the animals exhibited clinical signs of CWD during the study, we determined that all three cervid species were excreting CWD prions by 6 months post-inoculation. Faecal samples were consistently positive for CWD prions for all three cervid species (88 %), and were more likely to be positive than urine samples (28 %). Cervids with genotypes encoding for the prion protein (PRNP) that were considered to be more susceptible to CWD were more likely to excrete CWD prions (94 %) than cervids with genotypes considered to be less susceptible (64 %). All cervids with CWD prions in their urine also had positive faeces (n=5), but the converse was not true. Our study is the first to demonstrate CWD prion excretion in urine by asymptomatic elk and mule deer. Our results indicate that the excretion of CWD prions in faeces and, to a lesser extent, urine may provide an important avenue for depositing prions in the environment.
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Affiliation(s)
- Ian H Plummer
- Department of Forest and Wildlife Ecology, University of Wisconsin - Madison, 1630 Linden Drive, Madison, WI 53706, USA
| | - Scott D Wright
- US Geological Survey, National Wildlife Health Center, 6006 Schroeder Road, Madison, Wisconsin 53711, USA.,Present address: 4730 Toepfer Road, Middleton, Wisconsin 53562, USA
| | - Chad J Johnson
- Departments of Soil Science, Civil and Environmental Engineering, and Chemistry, University of Wisconsin - Madison, 1525 Observatory Drive, Madison, Wisconsin 53706, USA
| | - Joel A Pedersen
- Departments of Soil Science, Civil and Environmental Engineering, and Chemistry, University of Wisconsin - Madison, 1525 Observatory Drive, Madison, Wisconsin 53706, USA
| | - Michael D Samuel
- Retired, US Geological Survey, Wisconsin Cooperative Wildlife Research Unit, University of Wisconsin - Madison, 204 Russell Labs, 1630 Linden Drive, Madison, WI 53706, USA
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14
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Infectious Prions in the Pregnancy Microenvironment of Chronic Wasting Disease-Infected Reeves' Muntjac Deer. J Virol 2017; 91:JVI.00501-17. [PMID: 28539446 DOI: 10.1128/jvi.00501-17] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 05/05/2017] [Indexed: 11/20/2022] Open
Abstract
Ample evidence exists for the presence of infectious agents at the maternal-fetal interface, often with grave outcomes to the developing fetus (i.e., Zika virus, brucella, cytomegalovirus, and toxoplasma). While less studied, pregnancy-related transmissible spongiform encephalopathies (TSEs) have been implicated in several species, including humans. Our previous work has shown that prions can be transferred from mother to offspring, resulting in the development of clinical TSE disease in offspring born to muntjac dams infected with chronic wasting disease (CWD) (1). We further demonstrated protein misfolding cyclic amplification (PMCA)-competent prions within the female reproductive tract and in fetal tissues harvested from CWD experimentally and naturally exposed cervids (1, 2). To assess whether the PMCA-competent prions residing at the maternal-fetal interface were infectious and to determine if the real-time quaking-induced conversion (RT-QuIC) methodology may enhance our ability to detect amyloid fibrils within the pregnancy microenvironment, we employed a mouse bioassay and RT-QuIC. In this study, we have demonstrated RT-QuIC seeding activity in uterus, placentome, ovary, and amniotic fluid but not in allantoic fluids harvested from CWD-infected Reeves' muntjac dams showing clinical signs of infection (clinically CWD-infected) and in some placentomes from pre-clinically CWD-infected dams. Prion infectivity was confirmed within the uterus, amniotic fluid, and the placentome, the semipermeable interface that sustains the developing fetus, of CWD-infected dams. This is the first report of prion infectivity within the cervid pregnancy microenvironment, revealing a source of fetal CWD exposure prior to the birthing process, maternal grooming, or encounters with contaminated environments.IMPORTANCE The facile dissemination of chronic wasting disease within captive and free-range cervid populations has led to questions regarding the transmission dynamics of this disease. Direct contact with infected animals and indirect contact with infectious prions in bodily fluids and contaminated environments are suspected to explain the majority of this transmission. A third mode of transmission, from mother to offspring, may be underappreciated. The presence of pregnancy-related prion infectivity within the uterus, amniotic fluid, and the placental structure reveals that the developing fetus is exposed to a source of prions long before exposure to the infectious agent during and after the birthing process or via contact with contaminated environments. These findings have impact on our current concept of CWD disease transmission.
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15
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Adams DB. Prenatal transmission of scrapie in sheep and goats: A case study for veterinary public health. Open Vet J 2016; 6:194-214. [PMID: 27928518 PMCID: PMC5133396 DOI: 10.4314/ovj.v6i3.8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 10/26/2016] [Indexed: 01/11/2023] Open
Abstract
Unsettled knowledge as to whether scrapie transmits prenatally in sheep and goats and transmits by semen and preimplantation embryos has a potential to compromise measures for controlling, preventing and eliminating the disease. The remedy may be analysis according to a systematic review, allowing comprehensive and accessible treatment of evidence and reasoning, clarifying the issue and specifying the uncertainties. Systematic reviews have clearly formulated questions, can identify relevant studies and appraise their quality and can summarise evidence and reasoning with an explicit methodology. The present venture lays a foundation for a possible systematic review and applies three lines of evidence and reasoning to two questions. The first question is whether scrapie transmits prenatally in sheep and goats. It leads to the second question, which concerns the sanitary safety of artificial breeding technologies, and is whether scrapie transmits in sheep and goats by means of semen and washed or unwashed in vivo derived embryos. The three lines of evidence derive from epidemiological, field and clinical studies, experimentation, and causal reasoning, where inferences are made from the body of scientific knowledge and an understanding of animal structure and function. Evidence from epidemiological studies allow a conclusion that scrapie transmits prenatally and that semen and embryos are presumptive hazards for the transmission of scrapie. Evidence from experimentation confirms that semen and washed or unwashed in vivo derived embryos are hazards for the transmission of scrapie. Evidence from causal reasoning, including experience from other prion diseases, shows that mechanisms exist for prenatal transmission and transmission by semen and embryos in both sheep and goats.
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Affiliation(s)
- D B Adams
- 24 Noala Street, Aranda, ACT 2614, Australia
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16
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Cheng YC, Hannaoui S, John TR, Dudas S, Czub S, Gilch S. Early and Non-Invasive Detection of Chronic Wasting Disease Prions in Elk Feces by Real-Time Quaking Induced Conversion. PLoS One 2016; 11:e0166187. [PMID: 27829062 PMCID: PMC5102397 DOI: 10.1371/journal.pone.0166187] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 10/24/2016] [Indexed: 01/08/2023] Open
Abstract
Chronic wasting disease (CWD) is a fatal prion disease of wild and captive cervids in North America. Prions are infectious agents composed of a misfolded version of a host-encoded protein, termed PrPSc. Infected cervids excrete and secrete prions, contributing to lateral transmission. Geographical distribution is expanding and case numbers in wild cervids are increasing. Recently, the first European cases of CWD have been reported in a wild reindeer and two moose from Norway. Therefore, methods to detect the infection early in the incubation time using easily available samples are desirable to facilitate effective disease management. We have adapted the real-time quaking induced conversion (RT-QuIC) assay, a sensitive in vitro prion amplification method, for pre-clinical detection of prion seeding activity in elk feces. Testing fecal samples from orally inoculated elk taken at various time points post infection revealed early shedding and detectable prion seeding activity throughout the disease course. Early shedding was also found in two elk encoding a PrP genotype associated with reduced susceptibility for CWD. In summary, we suggest that detection of CWD prions in feces by RT-QuIC may become a useful tool to support CWD surveillance in wild and captive cervids. The finding of early shedding independent of the elk’s prion protein genotype raises the question whether prolonged survival is beneficial, considering accumulation of environmental prions and its contribution to CWD transmission upon extended duration of shedding.
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Affiliation(s)
- Yo Ching Cheng
- Dept. of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada
| | - Samia Hannaoui
- Dept. of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada
| | - Theodore R. John
- Dept. of Molecular Biology, University of Wyoming, Laramie, United States of America
| | - Sandor Dudas
- Canadian Food Inspection Agency, Lethbridge Laboratories, Lethbridge, Canada
| | - Stefanie Czub
- Canadian Food Inspection Agency, Lethbridge Laboratories, Lethbridge, Canada
| | - Sabine Gilch
- Dept. of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada
- * E-mail:
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17
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Niedermeyer S, Eiden M, Toumazos P, Papasavva-Stylianou P, Ioannou I, Sklaviadis T, Panagiotidis C, Langeveld J, Bossers A, Kuczius T, Kaatz M, Groschup MH, Fast C. Genetic, histochemical and biochemical studies on goat TSE cases from Cyprus. Vet Res 2016; 47:99. [PMID: 27716411 PMCID: PMC5053211 DOI: 10.1186/s13567-016-0379-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 08/24/2016] [Indexed: 11/12/2022] Open
Abstract
Scrapie and bovine spongiform encephalopathy (BSE) are transmissible spongiform encephalopathies (TSE’s) affecting sheep and goats. Susceptibility of goats to scrapie is influenced by polymorphisms of the prion protein gene (PRNP) of the host. Five polymorphisms are associated with reduced susceptibility to TSE’s. In the study presented here caprine samples from a scrapie eradication program on Cyprus were genotyped and further characterized using BioRad TeSeE rapid test, histological, immunohistochemical and biochemical methods. In total 42 goats from 20 flocks were necropsied from which 25 goats showed a positive result in the rapid test, a spongiform encephalopathy and an accumulation of pathological prion protein (PrPSc) in the obex. PrPSc deposits were demonstrated in the placenta, peripheral nervous and lymphoreticular system. Two animals showed PrPSc-accumulations in peripheral tissues only. By discriminatory immunoblots a scrapie infection could be confirmed for all cases. Nevertheless, slight deviations in the glycosylation pattern might indicate the presence of different scrapie strains. Furthermore scrapie samples from goats in the current study demonstrated less long term resistance to proteinase K than ovine or caprine BSE control samples. Reduced scrapie susceptibility according to the PRNP genotype was demonstrated (Fishers Exact test, p < 0.05) for the goats with at least one polymorphism (p = 0.023) at the six codons examined and in particular for those with polymorphisms at codon 146 (p = 0.016). This work characterizes scrapie in goats having implications for breeding and surveillance strategies.
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Affiliation(s)
- Susanne Niedermeyer
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institute, Südufer 10, 17493, Greifswald-Isle of Riems, Germany
| | - Martin Eiden
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institute, Südufer 10, 17493, Greifswald-Isle of Riems, Germany
| | - Pavlos Toumazos
- Veterinary Services, Ministry of Agriculture, Rural Development and Environment, 1417, Nicosia, Cyprus
| | | | - Ioannis Ioannou
- Veterinary Services, Ministry of Agriculture, Rural Development and Environment, 1417, Nicosia, Cyprus
| | - Theodoros Sklaviadis
- Laboratory of Pharmacology, School of Pharmacy, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Cynthia Panagiotidis
- Laboratory of Pharmacology, School of Pharmacy, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Jan Langeveld
- Department of Infection Biology, Central Veterinary Institute of Wageningen UR, Lelystad, The Netherlands
| | - Alex Bossers
- Department of Infection Biology, Central Veterinary Institute of Wageningen UR, Lelystad, The Netherlands
| | - Thorsten Kuczius
- Institute for Hygiene, Westfälische Wilhelms-University and University Hospital Münster, Robert Koch-Strasse 41, 48149, Münster, Germany
| | - Martin Kaatz
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institute, Südufer 10, 17493, Greifswald-Isle of Riems, Germany
| | - Martin H Groschup
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institute, Südufer 10, 17493, Greifswald-Isle of Riems, Germany
| | - Christine Fast
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institute, Südufer 10, 17493, Greifswald-Isle of Riems, Germany.
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18
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Requena JR, Kristensson K, Korth C, Zurzolo C, Simmons M, Aguilar-Calvo P, Aguzzi A, Andreoletti O, Benestad SL, Böhm R, Brown K, Calgua B, del Río JA, Espinosa JC, Girones R, Godsave S, Hoelzle LE, Knittler MR, Kuhn F, Legname G, Laeven P, Mabbott N, Mitrova E, Müller-Schiffmann A, Nuvolone M, Peters PJ, Raeber A, Roth K, Schmitz M, Schroeder B, Sonati T, Stitz L, Taraboulos A, Torres JM, Yan ZX, Zerr I. The Priority position paper: Protecting Europe's food chain from prions. Prion 2016; 10:165-81. [PMID: 27220820 PMCID: PMC4981192 DOI: 10.1080/19336896.2016.1175801] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 03/28/2016] [Accepted: 04/01/2016] [Indexed: 01/09/2023] Open
Abstract
Bovine spongiform encephalopathy (BSE) created a global European crisis in the 1980s and 90s, with very serious health and economic implications. Classical BSE now appears to be under control, to a great extent as a result of a global research effort that identified the sources of prions in meat and bone meal (MBM) and developed new animal-testing tools that guided policy. Priority ( www.prionpriority.eu ) was a European Union (EU) Framework Program 7 (FP7)-funded project through which 21 European research institutions and small and medium enterprises (SMEs) joined efforts between 2009 and 2014, to conduct coordinated basic and applied research on prions and prion diseases. At the end of the project, the Priority consortium drafted a position paper ( www.prionpriority.eu/Priority position paper) with its main conclusions. In the present opinion paper, we summarize these conclusions. With respect to the issue of re-introducing ruminant protein into the feed-chain, our opinion is that sustaining an absolute ban on feeding ruminant protein to ruminants is essential. In particular, the spread and impact of non-classical forms of scrapie and BSE in ruminants is not fully understood and the risks cannot be estimated. Atypical prion agents will probably continue to represent the dominant form of prion diseases in the near future in Europe. Atypical L-type BSE has clear zoonotic potential, as demonstrated in experimental models. Similarly, there are now data indicating that the atypical scrapie agent can cross various species barriers. More epidemiological data from large cohorts are necessary to reach any conclusion on the impact of its transmissibility on public health. Re-evaluations of safety precautions may become necessary depending on the outcome of these studies. Intensified searching for molecular determinants of the species barrier is recommended, since this barrier is key for important policy areas and risk assessment. Understanding the structural basis for strains and the basis for adaptation of a strain to a new host will require continued fundamental research, also needed to understand mechanisms of prion transmission, replication and how they cause nervous system dysfunction and death. Early detection of prion infection, ideally at a preclinical stage, also remains crucial for development of effective treatment strategies.
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Affiliation(s)
- Jesús R. Requena
- CIMUS Biomedical Research Institute, University of Santiago de Compostela, Santiago de Compostela, Spain
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Sue Godsave
- Netherlands Cancer Institute, Amsterdam, The Netherlands
| | | | | | | | | | - Paul Laeven
- University of Maastricht, Maastricht, The Netherlands
| | | | - Eva Mitrova
- Medical University of Slovakia, Bratislava, Slovakia
| | | | | | - Peter J. Peters
- The Maastricht Multimodal Molecular Imaging Institute, University of Maastricht, Maastricht, The Netherlands
| | | | | | | | | | | | - Lothar Stitz
- Friedrich Löffler Institut, Insel Reims, Germany
| | | | | | | | - Inga Zerr
- Universitätmedizin Göttingen, Göttingen, Germany
- German Center for Neurodegenerative Diseases (DZNE), Göttingen, Germany
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19
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Pan SY, Gao SH, Lin RC, Zhou SF, Dong HG, Tang MK, Yu ZL, Ko KM. New perspectives on dietary-derived treatments and food safety-antinomy in a new era. Crit Rev Food Sci Nutr 2016; 55:1836-59. [PMID: 24915382 DOI: 10.1080/10408398.2011.654286] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Despite the advances in science and technology and wide use of chemical drugs, dietary intervention (or food therapy) remains useful in preventing or treating many human diseases. A huge body of evidence shows that the dietary pattern or habit is also an important contributing factor to the development of chronic diseases such as hypertension, type 2 diabetes, hyperlipidemia, and cancers. In recent years, over-the-counter health foods, nutraceuticals, and plant-derived medicinal products have been gaining popularity all over the world, particularly in developed countries. Unfortunately, owing to the contamination with various harmful substances in foods and the presence of toxic food components, food-borne diseases have also become increasingly problematic. Incidents of food poisonings or tainted food have been increasing worldwide, particularly in China and other developing countries. Therefore, the government should put in a greater effort in enforcing food safety by improving the surveillance mechanism and exerting highest standards of quality control for foods.
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Affiliation(s)
- Si-Yuan Pan
- a Beijing University of Chinese Medicine , Beijing , China
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20
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Konold T, Hawkins SAC, Thurston LC, Maddison BC, Gough KC, Duarte A, Simmons HA. Objects in Contact with Classical Scrapie Sheep Act as a Reservoir for Scrapie Transmission. Front Vet Sci 2015; 2:32. [PMID: 26664961 PMCID: PMC4672192 DOI: 10.3389/fvets.2015.00032] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 08/24/2015] [Indexed: 11/13/2022] Open
Abstract
Classical scrapie is an environmentally transmissible prion disease of sheep and goats. Prions can persist and remain potentially infectious in the environment for many years and thus pose a risk of infecting animals after re-stocking. In vitro studies using serial protein misfolding cyclic amplification (sPMCA) have suggested that objects on a scrapie-affected sheep farm could contribute to disease transmission. This in vivo study aimed to determine the role of field furniture (water troughs, feeding troughs, fencing, and other objects that sheep may rub against) used by a scrapie-infected sheep flock as a vector for disease transmission to scrapie-free lambs with the prion protein genotype VRQ/VRQ, which is associated with high susceptibility to classical scrapie. When the field furniture was placed in clean accommodation, sheep became infected when exposed to either a water trough (four out of five) or to objects used for rubbing (four out of seven). This field furniture had been used by the scrapie-infected flock 8 weeks earlier and had previously been shown to harbor scrapie prions by sPMCA. Sheep also became infected (20 out of 23) through exposure to contaminated field furniture placed within pasture not used by scrapie-infected sheep for 40 months, even though swabs from this furniture tested negative by PMCA. This infection rate decreased (1 out of 12) on the same paddock after replacement with clean field furniture. Twelve grazing sheep exposed to field furniture not in contact with scrapie-infected sheep for 18 months remained scrapie free. The findings of this study highlight the role of field furniture used by scrapie-infected sheep to act as a reservoir for disease re-introduction although infectivity declines considerably if the field furniture has not been in contact with scrapie-infected sheep for several months. PMCA may not be as sensitive as VRQ/VRQ sheep to test for environmental contamination.
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Affiliation(s)
- Timm Konold
- Animal Sciences Unit, Animal and Plant Health Agency Weybridge , Addlestone , UK
| | - Stephen A C Hawkins
- Pathology Department, Animal and Plant Health Agency Weybridge , Addlestone , UK
| | - Lisa C Thurston
- Surveillance and Laboratory Services, Animal and Plant Health Agency Penrith , Penrith , UK
| | - Ben C Maddison
- ADAS UK, School of Veterinary Medicine and Science, University of Nottingham , Sutton Bonington , UK
| | - Kevin C Gough
- School of Veterinary Medicine and Science, University of Nottingham , Sutton Bonington , UK
| | - Anthony Duarte
- Animal Sciences Unit, Animal and Plant Health Agency Weybridge , Addlestone , UK
| | - Hugh A Simmons
- Animal Sciences Unit, Animal and Plant Health Agency Weybridge , Addlestone , UK
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21
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Longitudinal Detection of Prion Shedding in Saliva and Urine by Chronic Wasting Disease-Infected Deer by Real-Time Quaking-Induced Conversion. J Virol 2015; 89:9338-47. [PMID: 26136567 DOI: 10.1128/jvi.01118-15] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 06/23/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Chronic wasting disease (CWD) is an emergent, rapidly spreading prion disease of cervids. Shedding of infectious prions in saliva and urine is thought to be an important factor in CWD transmission. To help to elucidate this issue, we applied an in vitro amplification assay to determine the onset, duration, and magnitude of prion shedding in longitudinally collected saliva and urine samples from CWD-exposed white-tailed deer. We detected prion shedding as early as 3 months after CWD exposure and sustained shedding throughout the disease course. We estimated that the 50% lethal dose (LD50) for cervidized transgenic mice would be contained in 1 ml of infected deer saliva or 10 ml of urine. Given the average course of infection and daily production of these body fluids, an infected deer would shed thousands of prion infectious doses over the course of CWD infection. The direct and indirect environmental impacts of this magnitude of prion shedding on cervid and noncervid species are surely significant. IMPORTANCE Chronic wasting disease (CWD) is an emerging and uniformly fatal prion disease affecting free-ranging deer and elk and is now recognized in 22 U.S. states and 2 Canadian provinces. It is unique among prion diseases in that it is transmitted naturally through wild populations. A major hypothesis to explain CWD's florid spread is that prions are shed in excreta and transmitted via direct or indirect environmental contact. Here we use a rapid in vitro assay to show that infectious doses of CWD prions are in fact shed throughout the multiyear disease course in deer. This finding is an important advance in assessing the risks posed by shed CWD prions to animals as well as humans.
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Pritzkow S, Morales R, Moda F, Khan U, Telling GC, Hoover E, Soto C. Grass plants bind, retain, uptake, and transport infectious prions. Cell Rep 2015; 11:1168-75. [PMID: 25981035 DOI: 10.1016/j.celrep.2015.04.036] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 02/04/2015] [Accepted: 04/15/2015] [Indexed: 01/07/2023] Open
Abstract
Prions are the protein-based infectious agents responsible for prion diseases. Environmental prion contamination has been implicated in disease transmission. Here, we analyzed the binding and retention of infectious prion protein (PrP(Sc)) to plants. Small quantities of PrP(Sc) contained in diluted brain homogenate or in excretory materials (urine and feces) can bind to wheat grass roots and leaves. Wild-type hamsters were efficiently infected by ingestion of prion-contaminated plants. The prion-plant interaction occurs with prions from diverse origins, including chronic wasting disease. Furthermore, leaves contaminated by spraying with a prion-containing preparation retained PrP(Sc) for several weeks in the living plant. Finally, plants can uptake prions from contaminated soil and transport them to aerial parts of the plant (stem and leaves). These findings demonstrate that plants can efficiently bind infectious prions and act as carriers of infectivity, suggesting a possible role of environmental prion contamination in the horizontal transmission of the disease.
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Affiliation(s)
- Sandra Pritzkow
- Mitchell Center for Alzheimer's Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, 6431 Fannin Street, Houston, TX 77030, USA
| | - Rodrigo Morales
- Mitchell Center for Alzheimer's Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, 6431 Fannin Street, Houston, TX 77030, USA
| | - Fabio Moda
- Mitchell Center for Alzheimer's Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, 6431 Fannin Street, Houston, TX 77030, USA
| | - Uffaf Khan
- Mitchell Center for Alzheimer's Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, 6431 Fannin Street, Houston, TX 77030, USA
| | - Glenn C Telling
- Prion Research Center, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Edward Hoover
- Prion Research Center, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Claudio Soto
- Mitchell Center for Alzheimer's Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, 6431 Fannin Street, Houston, TX 77030, USA.
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Gough KC, Baker CA, Simmons HA, Hawkins SA, Maddison BC. Circulation of prions within dust on a scrapie affected farm. Vet Res 2015; 46:40. [PMID: 25889731 PMCID: PMC4397813 DOI: 10.1186/s13567-015-0176-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 03/30/2015] [Indexed: 11/14/2022] Open
Abstract
Prion diseases are fatal neurological disorders that affect humans and animals. Scrapie of sheep/goats and Chronic Wasting Disease (CWD) of deer/elk are contagious prion diseases where environmental reservoirs have a direct link to the transmission of disease. Using protein misfolding cyclic amplification we demonstrate that scrapie PrPSc can be detected within circulating dusts that are present on a farm that is naturally contaminated with sheep scrapie. The presence of infectious scrapie within airborne dusts may represent a possible route of infection and illustrates the difficulties that may be associated with the effective decontamination of such scrapie affected premises.
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Affiliation(s)
- Kevin C Gough
- School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington, Loughborough, Leicestershire, LE12 5RD, UK.
| | - Claire A Baker
- ADAS UK, School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington, Loughborough, Leicestershire, LE12 5RD, UK.
| | - Hugh A Simmons
- Animal and Plant Health Agency, Woodham Lane, New Haw, Addlestone, Surrey, KT15 3NB, UK.
| | - Steve A Hawkins
- Animal and Plant Health Agency, Woodham Lane, New Haw, Addlestone, Surrey, KT15 3NB, UK.
| | - Ben C Maddison
- ADAS UK, School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington, Loughborough, Leicestershire, LE12 5RD, UK.
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Hawkins SAC, Simmons HA, Gough KC, Maddison BC. Persistence of ovine scrapie infectivity in a farm environment following cleaning and decontamination. Vet Rec 2014; 176:99. [PMID: 25362003 DOI: 10.1136/vr.102743] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Scrapie of sheep/goats and chronic wasting disease of deer/elk are contagious prion diseases where environmental reservoirs are directly implicated in the transmission of disease. In this study, the effectiveness of recommended scrapie farm decontamination regimens was evaluated by a sheep bioassay using buildings naturally contaminated with scrapie. Pens within a farm building were treated with either 20,000 parts per million free chorine solution for one hour or were treated with the same but were followed by painting and full re-galvanisation or replacement of metalwork within the pen. Scrapie susceptible lambs of the PRNP genotype VRQ/VRQ were reared within these pens and their scrapie status was monitored by recto-anal mucosa-associated lymphoid tissue. All animals became infected over an 18-month period, even in the pen that had been subject to the most stringent decontamination process. These data suggest that recommended current guidelines for the decontamination of farm buildings following outbreaks of scrapie do little to reduce the titre of infectious scrapie material and that environmental recontamination could also be an issue associated with these premises.
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Affiliation(s)
- Steve A C Hawkins
- Animal and Plant Health Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - Hugh A Simmons
- Animal and Plant Health Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - Kevin C Gough
- School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington, Loughborough, Leicestershire LE12 5RD, UK
| | - Ben C Maddison
- ADAS UK, School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington, Loughborough, Leicestershire LE12 5RD, UK
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25
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Balcomb C, Foster D. Update on the Use of Blood and Blood Products in Ruminants. Vet Clin North Am Food Anim Pract 2014; 30:455-74, vii. [DOI: 10.1016/j.cvfa.2014.04.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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26
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Small-molecule theranostic probes: a promising future in neurodegenerative diseases. Int J Cell Biol 2013; 2013:150952. [PMID: 24324497 PMCID: PMC3845517 DOI: 10.1155/2013/150952] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 09/03/2013] [Indexed: 12/15/2022] Open
Abstract
Prion diseases are fatal neurodegenerative illnesses, which include Creutzfeldt-Jakob disease in humans and scrapie, chronic wasting disease, and bovine spongiform encephalopathy in animals. They are caused by unconventional infectious agents consisting primarily of misfolded, aggregated, β -sheet-rich isoforms, denoted prions, of the physiological cellular prion protein (PrP(C)). Many lines of evidence suggest that prions (PrP(Sc)) act both as a template for this conversion and as a neurotoxic agent causing neuronal dysfunction and cell death. As such, PrP(Sc) may be considered as both a neuropathological hallmark of the disease and a therapeutic target. Several diagnostic imaging probes have been developed to monitor cerebral amyloid lesions in patients with neurodegenerative disorders (such as Alzheimer's disease, Parkinson's disease, and prion disease). Examples of these probes are Congo red, thioflavin T, and their derivatives. We synthesized a series of styryl derivatives, denoted theranostics, and studied their therapeutic and/or diagnostic potentials. Here we review the salient traits of these small molecules that are able to detect and modulate aggregated forms of several proteins involved in protein misfolding diseases. We then highlight the importance of further studies for their practical implications in therapy and diagnostics.
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Goss MJ, Tubeileh A, Goorahoo D. A Review of the Use of Organic Amendments and the Risk to Human Health. ADVANCES IN AGRONOMY 2013; 120. [PMCID: PMC7173535 DOI: 10.1016/b978-0-12-407686-0.00005-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Historically, organic amendments—organic wastes—have been the main source of plant nutrients, especially N. Their use allows better management of often-finite resources to counter changes in soils that result from essential practices for crop production. Organic amendments provide macro- and micronutrients, including carbon for the restoration of soil physical and chemical properties. Challenges from the use of organic amendments arise from the presence of heavy metals and the inability to control the transformations required to convert the organic forms of N and P into the minerals available to crops, and particularly to minimize the losses of these nutrients in forms that may present a threat to human health. Animal manure and sewage biosolids, the organic amendments in greatest abundance, contain components that can be hazardous to human health, other animals and plants. Pathogens pose an immediate threat. Antibiotics, other pharmaceuticals and naturally produced hormones may pose a threat if they increase the number of zoonotic disease organisms that are resistant to multiple antimicrobial drugs or interfere with reproductive processes. Some approaches aimed at limiting N losses (e.g. covered liquid or slurry storage, rapid incorporation into the soil, timing applications to minimize delay before plant uptake) also tend to favor survival of pathogens. Risks to human health, through the food chain and drinking water, from the pathogens, antibiotics and hormonal substances that may be present in organic amendments can be reduced by treatment before land application, such as in the case of sewage biosolids. Other sources, such as livestock and poultry manures, are largely managed by ensuring that they are applied at the rate, time and place most appropriate to the crops and soils. A more holistic approach to management is required as intensification of agriculture increases.
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Affiliation(s)
- Michael J. Goss
- University of Guelph, Kemptville Campus, Kemptville, ON, Canada
- Corresponding author: E-mail:
| | - Ashraf Tubeileh
- University of Guelph, Kemptville Campus, Kemptville, ON, Canada
| | - Dave Goorahoo
- Plant Science Department, California State University, Fresno, CA, USA
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Taema MM, Maddison BC, Thorne L, Bishop K, Owen J, Hunter N, Baker CA, Terry LA, Gough KC. Differentiating ovine BSE from CH1641 scrapie by serial protein misfolding cyclic amplification. Mol Biotechnol 2012; 51:233-9. [PMID: 21987099 DOI: 10.1007/s12033-011-9460-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Whilst ovine BSE displays distinct pathological characteristics to ovine CH1641-like scrapie upon passage in rodents, they have very similar molecular phenotypes. As such, the in vitro differentiation of these strains in routine surveillance programmes presents a significant diagnostic challenge. In this study, using serial protein-misfolding cyclic amplification (sPMCA), ovine BSE was readily amplified in vitro in brain substrates from sheep with V₁₃₆R₁₅₄Q₁₇₁/V₁₃₆R₁₅₄Q₁₇₁ or AHQ/AHQ PRNP genotypes. In contrast, the CH1641 strain was refractory to such amplification. This method allowed for complete and unequivocal differentiation of experimental BSE from CH1641 prion strains within an ovine host.
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Affiliation(s)
- Maged M Taema
- School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington Campus, College Road, Sutton Bonington, Leicestershire LE12 5RD, UK
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Thorne L, Holder T, Ramsay A, Edwards J, Taema MM, Windl O, Maddison BC, Gough KC, Terry LA. In vitro amplification of ovine prions from scrapie-infected sheep from Great Britain reveals distinct patterns of propagation. BMC Vet Res 2012; 8:223. [PMID: 23153009 PMCID: PMC3559253 DOI: 10.1186/1746-6148-8-223] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 10/30/2012] [Indexed: 11/12/2022] Open
Abstract
Background Protein misfolding cyclic amplification (PMCA) is a method that facilitates the detection of prions from many sources of transmissible spongiform encephalopathy (TSE). Sheep scrapie represents a unique diversity of prion disease agents in a range of susceptible PRNP genotypes. In this study PMCA was assessed on a range of Great Britain (GB) sheep scrapie isolates to determine the applicability to veterinary diagnosis of ovine TSE. Results PrPSc amplification by protein misfolding cyclic amplification (PMCA) was assessed as a diagnostic tool for field cases of scrapie. The technique was initially applied to thirty-seven isolates of scrapie from diverse geographical locations around GB, and involved sheep of various breeds and PRNP genotypes. All samples were amplified in either VRQ and/or ARQ PrPC substrate. For PrPSc from sheep with at least one VRQ allele, all samples amplified efficiently in VRQ PrPC but only PrPSc from ARH/VRQ sheep amplified in both substrates. PrPSc from ARQ/ARQ sheep displayed two amplification patterns, one that amplified in both substrates and one that only amplified in ARQ PrPC. These amplification patterns were consistent for a further 14/15 flock/farm mates of these sheep. Furthermore experimental scrapie strains SSBP1, Dawson, CH1641 and MRI were analysed. SSBP1 and Dawson (from VRQ/VRQ sheep) amplified in VRQ but not ARQ substrate. MRI scrapie (from ARQ/ARQ sheep) nor CH1641 did not amplify in ARQ or VRQ substrate; these strains required an enhanced PMCA method incorporating polyadenylic acid (poly(A)) to achieve amplification. Conclusions PrPsc from 52 classical scrapie GB field isolates amplified in VRQ or ARQ or both substrates and supports the use of PMCA as a rapid assay for the detection of a wide range of ovine classical scrapie infections involving multiple PRNP genotypes and scrapie strains.
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Affiliation(s)
- Leigh Thorne
- Animal Health Veterinary Laboratories Agency (AHVLA), New Haw, Addlestone, Surrey, UK
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Maluquer de Motes C, Espinosa JC, Esteban A, Calvo M, Girones R, Torres JM. Persistence of the bovine spongiform encephalopathy infectious agent in sewage. ENVIRONMENTAL RESEARCH 2012; 117:1-7. [PMID: 22776326 DOI: 10.1016/j.envres.2012.06.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 05/28/2012] [Accepted: 06/18/2012] [Indexed: 06/01/2023]
Abstract
Horizontal transmission of prion diseases through the environment represents a considerable concern. Prions are extremely resistant to inactivation and are thought to enter the environment after burial of animal mortalities or through biosolids from wastewater treatment plants. In addition, deposition of prions in the environment through biological fluids and/or faeces has been proved in the last years. Little is known about the behaviour of prion infectivity in the environment. In this study, the persistence of BSE infectious agent in sewage has been assessed by both PrP(Res) immunoblotting and mouse bioassay in a long-term incubation study. Results indicated that no PrP(Res) was detected after 150 day of incubation and consistent with this, a statistical regression model estimated 2-logs decay in 151 day. In contrast, no reduction in infectivity was observed during this period. Similarly, BSE infectivity remained unaltered after incubation in PBS for 265 day, whereas PrP(Res) levels dropped progressively over the length of the study. These results indicate that in sewage and PBS, prion infectivity persists longer and with different dynamics than its commonly used marker PrP(Res). Thus, mathematical models computed on the basis of PrP(Res) detection were unable to predict inactivation of prion infectivity. It is also reasonable to assume that conventional wastewater treatments with low retention times could have a very limited impact on prion infectivity. This data is essential for the development of accurate risk assessment analysis for BSE and other prion diseases in the environment.
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Maddison BC, Owen JP, Taema MM, Shaw G, Gough KC. Temperature influences the interaction of ruminant PrP (TSE) with soil. Prion 2012; 6:302-8. [PMID: 22561162 DOI: 10.4161/pri.20025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Ovine scrapie and cervid chronic wasting disease can be transmitted in the absence of animal-to-animal contact, and environmental reservoirs of infectivity have been implicated in their spread and persistence. Investigating environmental factors that influence the interaction of disease-associated PrP with soils is imperative to understanding what is likely to be the complex role of soil in disease transmission. Here, we describe the effects of soil temperature on the binding/desorption and persistence of both ovine scrapie- and bovine BSE-PrP (TSE) . Binding of PrP (TSE) to a sandy loam soil at temperatures of 4°C, 8-12°C and 25-30°C demonstrated that an increase in temperature resulted in (1) a decrease in the amount of PrP (TSE) recovered after 24 h of interaction with soil, (2) an increase in the amount of N-terminal cleavage of the prion protein over 11 d and (3) a decrease in the persistence of PrP (TSE) on soil over an 18 mo period.
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Affiliation(s)
- Ben C Maddison
- ADAS UK, School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington, Leicestershire, UK.
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Madsen-Bouterse SA, Zhuang D, O'Rourke KI, Schneider DA. Differential immunoreactivity of goat derived scrapie following in vitro misfolding versus mouse bioassay. Biochem Biophys Res Commun 2012; 423:770-4. [PMID: 22713450 DOI: 10.1016/j.bbrc.2012.06.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 06/11/2012] [Indexed: 02/01/2023]
Abstract
The protein misfolding cyclic amplification (PMCA) assay allows for detection of prion protein misfolding activity in tissues and fluids from sheep with scrapie where it was previously undetected by conventional western blot and immunohistochemistry assays. Studies of goats with scrapie have yet to take advantage of PMCA, which could aid in discerning the risk of transmission between goats and goats to sheep. The aim of the current study was to adapt PMCA for evaluation of scrapie derived from goats. Diluted brain homogenate from scrapie-infected goats (i.e., the scrapie seed, PrP(Sc)) was subjected to PMCA using normal brain homogenate from ovinized transgenic mice (tg338) as the source of normal cellular prion protein (the substrate, PrP(C)). The assay end-point was detection of the proteinase K-resistant misfolded prion protein core (PrP(res)) by western blot. Protein misfolding activity was consistently observed in caprine brain homogenate diluted 10,000-fold after 5 PMCA rounds. Epitope mapping by western blot analyses demonstrated that PrP(res) post-PMCA was readily detected with an N-terminus anti-PrP monoclonal antibody (P4), similar to scrapie inoculum from goats. This was in contrast to limited detection of PrP(res) with P4 following mouse bioassay. The inverse was observed with a monoclonal antibody to the C-terminus (F99/97.6.1). Thus, brain homogenate prepared from uninoculated tg338 served as an appropriate substrate for serial PMCA of PrP(Sc) derived from goats. These observations suggest that concurrent PMCA and bioassay with tg338 could improve characterization of goat derived scrapie.
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Affiliation(s)
- Sally A Madsen-Bouterse
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, USA.
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Böhnlein C, Groschup MH, Maertlbauer E, Pichner R, Gareis M. Stability of bovine spongiform encephalopathy prions: absence of prion protein degradation by bovine gut microbiota. Zoonoses Public Health 2012; 59:251-5. [PMID: 22353543 DOI: 10.1111/j.1863-2378.2012.01455.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Bovine spongiform encephalopathy (BSE) is transmitted by the oral route. However, the impacts of anaerobic fermentation processes in cattle on the stability of BSE-associated prion protein (PrP(Sc)) are still unresolved. In this study, experiments were designed to assess the ability of complex ruminal and colonic contents of bovines to degrade BSE-derived PrP(Sc). No significant decrease in PrP(Sc) levels in BSE brain homogenates was detected by Western blotting after up to 66 h of co-incubation with intestinal fluids. These results indicate that BSE-associated PrP(Sc) survive gastrointestinal digestion processes in cattle and might be excreted via faeces.
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Affiliation(s)
- C Böhnlein
- Institute for Microbiology and Biotechnology, Max-Rubner-Institute, Federal Research Institute for Nutrition and Food, Kulmbach, Germany.
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The oral secretion of infectious scrapie prions occurs in preclinical sheep with a range of PRNP genotypes. J Virol 2011; 86:566-71. [PMID: 22013047 DOI: 10.1128/jvi.05579-11] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Preclinical sheep with the highly scrapie-susceptible VRQ/VRQ PRNP genotype secrete prions from the oral cavity. In order to further understand the significance of orally available prions, buccal swabs were taken from sheep with a range of PRNP genotypes and analyzed by serial protein misfolding cyclic amplification (sPMCA). Prions were detected in buccal swabs from scrapie-exposed sheep of genotypes linked to high (VRQ/VRQ and ARQ/VRQ) and low (ARR/VRQ and AHQ/VRQ) lymphoreticular system involvement in scrapie pathogenesis. For both groups, the level of prion detection was significantly higher than that for scrapie-resistant ARR/ARR sheep which were kept in the same farm environment and acted as sentinel controls for prions derived from the environment which might contaminate the oral cavity. In addition, sheep with no exposure to the scrapie agent did not contain any measurable prions within the oral cavity. Furthermore, prions were detected in sheep over a wide age range representing various stages of preclinical disease. These data demonstrate that orally available scrapie prions may be a common feature in sheep incubating scrapie, regardless of the PRNP genotype and any associated high-level accumulation of PrP(Sc) within lymphoreticular tissues. PrP(Sc) was present in buccal swabs from a large proportion of sheep with PRNP genotypes associated with relatively low disease penetrance, indicating that subclinical scrapie infection is likely to be a common occurrence. The significance of positive sPMCA reactions was confirmed by the transmission of infectivity in buccal swab extracts to Tg338 mice, illustrating the likely importance of orally available prions in the horizontal transmission of scrapie.
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