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McIntyre KM, del Rio Vilas VJ, Gubbins S. No temporal trends in the prevalence of atypical scrapie in British sheep, 2002-2006. BMC Vet Res 2008; 4:13. [PMID: 18384678 PMCID: PMC2397389 DOI: 10.1186/1746-6148-4-13] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Accepted: 04/02/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND So-called atypical scrapie was first identified in Great Britain (GB) in 2002 following the introduction of wide-scale scrapie surveillance. In particular, abattoir and fallen stock surveys have been carried out in GB since 2002, with a total of 147 atypical positives identified by the end of 2006. The results of these surveys provide data with which to assess temporal trends in the prevalence of atypical scrapie in sheep in Great Britain between 2002 and 2006. RESULTS Using the results of abattoir and fallen stock surveys, the prevalence of atypical scrapie (percentage of samples positive) was estimated. The prevalence in the abattoir and fallen stock surveys, for all years combined, was 0.09% (95% confidence interval (CI): 0.08%-0.11%) and 0.07% (95% CI: 0.05%-0.11%), respectively. There were no significant temporal trends in either survey. Comparing the surveys' results, there were no significant differences in annual prevalence or the prevalence within PrP genotypes. For the abattoir survey, the PrP genotype with the highest prevalence was AHQ/AHQ, which was significantly higher than all other genotypes, except ARR/AHQ, AHQ/ARH and ARH/ARQ. CONCLUSION The estimated prevalence of atypical scrapie was similar in both the abattoir and fallen stock surveys. Our results indicate there was no significant temporal trend in prevalence, adding to evidence that this atypical form of scrapie may be a sporadic condition or, if it is infectious, that the force of infection is very low.
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Affiliation(s)
- K Marie McIntyre
- Institute for Animal Health, Pirbright Laboratory, Ash Road, Pirbright, Surrey GU24 0NF, UK.
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Böhning D, Rio Vilas VJ. Estimating the hidden number of scrapie affected holdings in Great Britain using a simple, truncated count model allowing for heterogeneity. JOURNAL OF AGRICULTURAL BIOLOGICAL AND ENVIRONMENTAL STATISTICS 2008. [DOI: 10.1198/108571108x277904] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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54
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Dawson M, Moore RC, Bishop SC. Progress and limits of PrP gene selection policy. Vet Res 2008; 39:25. [PMID: 18258168 DOI: 10.1051/vetres:2007064] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Accepted: 11/13/2007] [Indexed: 12/22/2022] Open
Abstract
Classical scrapie has proved to be a notoriously difficult disease to control due to a poor understanding of its natural history. The recognition of disease risk linkage to PrP genotype has offered the prospect of a disease control strategy, viz. genotyping and selective breeding, novel to veterinary medicine when first considered in the 1990s. The UK Spongiform Encephalopathy Advisory Committee recommended the exploitation of this approach in a voluntary, national programme to control classical scrapie and protect the public against food-borne exposure to bovine spongiform encephalopathy, should the national flock have been exposed via contaminated feed. The National Scrapie Plan for Great Britain was launched in 2001 and uptake has been widespread throughout the purebreeding sector of the sheep industry, with membership peaking at over 12 000 flocks in 2006. A total of 700 000 rams from 90 breeds have been genotyped. A comparison of ram lambs born in 2002 with those in 2006 shows evident changes in PrP genotype frequencies which are predicted to be associated with a reduction in disease risk. Various concerns have been raised regarding possible unintended consequences of widespread selection on PrP genotype, including impacts on other performance traits and possible effects on inbreeding and genetic diversity. To date, these concerns appear to be unfounded, as no consistent associations have been found with performance traits, nor are there likely to be any detectable impacts on inbreeding in mainstream breeds. Currently, semen banks have been implemented in Great Britain to store samples from animals of all common PrP genotypes, should these genotypes be required in the future. Various strategies to minimise future disease risks are discussed in the paper.
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Affiliation(s)
- Michael Dawson
- National Scrapie Plan Administration Centre, Animal Health, Worcester, WR5 2SU, UK.
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55
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Green DM, del Rio Vilas VJ, Birch CPD, Johnson J, Kiss IZ, McCarthy ND, Kao RR. Demographic risk factors for classical and atypical scrapie in Great Britain. J Gen Virol 2008; 88:3486-3492. [PMID: 18024920 PMCID: PMC2884981 DOI: 10.1099/vir.0.83225-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Following the bovine spongiform encephalopathy (BSE) crisis, the European Union has introduced policies for eradicating transmissible spongiform encephalopathies (TSEs), including scrapie, from large ruminants. However, recent European Union surveillance has identified a novel prion disease, ‘atypical’ scrapie, substantially different from classical scrapie. It is unknown whether atypical scrapie is naturally transmissible or zoonotic, like BSE. Furthermore, cases have occurred in scrapie-resistant genotypes that are targets for selection in legislated selective breeding programmes. Here, the first epidemiological study of British cases of atypical scrapie is described, focusing on the demographics and trading patterns of farms and using databases of recorded livestock movements. Triplet comparisons found that farms with atypical scrapie stock more sheep than those of the general, non-affected population. They also move larger numbers of animals than control farms, but similar numbers to farms reporting classical scrapie. Whilst there is weak evidence of association through sheep trading of farms reporting classical scrapie, atypical scrapie shows no such evidence, being well-distributed across regions of Great Britain and through the sheep-trading network. Thus, although cases are few in number so far, our study suggests that, should natural transmission of atypical scrapie be occurring at all, it is doing so slowly.
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Affiliation(s)
- Darren M. Green
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
| | | | - Colin P. D. Birch
- Veterinary Laboratories Agency, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - Jethro Johnson
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand
| | - Istvan Z. Kiss
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
| | - Noel D. McCarthy
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
| | - Rowland R. Kao
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
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56
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Benestad SL, Arsac JN, Goldmann W, Nöremark M. Atypical/Nor98 scrapie: properties of the agent, genetics, and epidemiology. Vet Res 2008; 39:19. [PMID: 18187032 DOI: 10.1051/vetres:2007056] [Citation(s) in RCA: 172] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Accepted: 10/23/2007] [Indexed: 11/14/2022] Open
Abstract
Atypical/Nor98 scrapie cases in sheep were diagnosed for the first time in Norway in 1998. They are now identified in small ruminants in most European countries and represent an increasingly large proportion of the scrapie cases diagnosed in Europe. Atypical/Nor98 scrapie isolates have shown to be experimentally transmissible into transgenic mice and sheep but the properties of the TSE agent involved, like its biological and biochemical features, are so clearly distinct from the agent involved in classical scrapie that they have provided a challenging diagnostic for many years. No strain diversity has yet been identified among the atypical/Nor98 scrapie sample cases. The genetic predisposition of the sheep affected by atypical/Nor98 scrapie is almost inverted compared to classical scrapie, and the exact origin of this sporadic TSE strain is still speculative, but a spontaneous, non-contagious origin, like sporadic Creutzfeldt-Jakob disease in humans, can not be excluded. Further transmission and epidemiological studies are needed to better address this hypothesis.
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57
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Fryer HR, Baylis M, Sivam K, McLean AR. Quantifying the risk from ovine BSE and the impact of control strategies. Proc Biol Sci 2008; 274:1497-503. [PMID: 17412681 PMCID: PMC2176166 DOI: 10.1098/rspb.2007.0353] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Although no naturally infected sheep with bovine spongiform encephalopathy (BSE) has ever been discovered, it remains possible that BSE once infected the UK sheep population, has been transmitted between sheep, and is still present today. We constructed a mathematical model to assess the current maximum theoretical exposure to consumers from BSE-infected ovine material and to estimate the risk reduction that could be achieved by abattoir-based control options if BSE-infected sheep were ever found in the national flock. We predict that, if present, the exposure to consumers from a single BSE-infected sheep would be high: one sheep, close to the end of its incubation period, is likely to contribute 10-1000 times more infectious material than a fully infectious cow. Furthermore, 30% of this exposure comes from infectivity residing in lymphatic and peripheral tissue that cannot be completely removed from a carcass. We are 95% confident that throughout Great Britain, no more than four sheep flocks currently harbour an ongoing BSE epidemic. However, since the exposure from a single infected sheep is high, the annual human exposure from four 'typical' BSE-infected flocks could be considerable. Small reductions in exposure could be achieved by strategies based on tissue testing, a 12-month age restriction or expanded definitions of high-risk tissues. A six-month age restriction is likely to be more effective and genotype-based strategies the most effective.
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Affiliation(s)
- Helen R Fryer
- Institute for Emergent Infections of Humans, James Martin 21st Century School, Department of Zoology, Oxford University, South Parks Road, Oxford OX1 3PS, UK.
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58
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Seuberlich T, Botteron C, Benestad SL, Brünisholz H, Wyss R, Kihm U, Schwermer H, Friess M, Nicolier A, Heim D, Zurbriggen A. Atypical scrapie in a Swiss goat and implications for transmissible spongiform encephalopathy surveillance. J Vet Diagn Invest 2007; 19:2-8. [PMID: 17459826 DOI: 10.1177/104063870701900102] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Different types of transmissible spongiform encephalopathies (TSEs) affect sheep and goats. In addition to the classical form of scrapie, both species are susceptible to experimental infections with the bovine spongiform encephalopathy (BSE) agent, and in recent years atypical scrapie cases have been reported in sheep from different European countries. Atypical scrapie in sheep is characterized by distinct histopathologic lesions and molecular characteristics of the abnormal scrapie prion protein (PrP(sc)). Characteristics of atypical scrapie have not yet been described in detail in goats. A goat presenting features of atypical scrapie was identified in Switzerland. Although there was no difference between the molecular characteristics of PrP(sc) in this animal and those of atypical scrapie in sheep, differences in the distribution of histopathologic lesions and PrP(sc) deposition were observed. In particular the cerebellar cortex, a major site of PrP(sc) deposition in atypical scrapie in sheep, was found to be virtually unaffected in this goat. In contrast, severe lesions and PrP(sc) deposition were detected in more rostral brain structures, such as thalamus and midbrain. Two TSE screening tests and PrP(sc) immunohistochemistry were either negative or barely positive when applied to cerebellum and obex tissues, the target samples for TSE surveillance in sheep and goats. These findings suggest that such cases may have been missed in the past and could be overlooked in the future if sampling and testing procedures are not adapted. The epidemiological and veterinary public health implications of these atypical cases, however, are not yet known.
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Affiliation(s)
- Torsten Seuberlich
- NeuroCenter, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, Bremgartenstrasse 109a, CH-3001 Berne, Switzerland.
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59
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Simmons MM, Konold T, Simmons HA, Spencer YI, Lockey R, Spiropoulos J, Everitt S, Clifford D. Experimental transmission of atypical scrapie to sheep. BMC Vet Res 2007; 3:20. [PMID: 17725818 PMCID: PMC2025597 DOI: 10.1186/1746-6148-3-20] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Accepted: 08/28/2007] [Indexed: 12/04/2022] Open
Abstract
Background Active surveillance for transmissible spongiform encephalopathies in small ruminants has been an EU regulatory requirement since 2002. A number of European countries have subsequently reported cases of atypical scrapie, similar to previously published cases from Norway, which have pathological and molecular features distinct from classical scrapie. Most cases have occurred singly in flocks, associated with genotypes considered to be more resistant to classical disease. Experimental transmissibility of such isolates has been reported in certain ovinised transgenic mice, but has not previously been reported in the natural host. Information on the transmissibility of this agent is vital to ensuring that disease control measures are effective and proportionate. Results This report presents the successful experimental transmission, in 378 days, of atypical scrapie to a recipient sheep of homologous genotype with preservation of the pathological and molecular characteristics of the donor. This isolate also transmitted to ovinised transgenic mice (Tg338) with a murine phenotype indistinguishable from that of Nor 98. Conclusion This result strengthens the opinion that these cases result from a distinct strain of scrapie agent, which is potentially transmissible in the natural host under field conditions.
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Affiliation(s)
- Marion M Simmons
- Department of Pathology, Veterinary Laboratories Agency – Weybridge, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - Timm Konold
- Department of Pathology, Veterinary Laboratories Agency – Weybridge, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - Hugh A Simmons
- Animal Services Unit, Veterinary Laboratories Agency – Weybridge, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - Yvonne I Spencer
- Department of Pathology, Veterinary Laboratories Agency – Weybridge, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - Richard Lockey
- Department of Pathology, Veterinary Laboratories Agency – Weybridge, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - John Spiropoulos
- Department of Pathology, Veterinary Laboratories Agency – Weybridge, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - Sharon Everitt
- Department of Molecular Pathogenesis and Genetics, Veterinary Laboratories Agency – Weybridge, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - Derek Clifford
- Animal Services Unit, Veterinary Laboratories Agency – Weybridge, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK
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60
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Jeffrey M, González L. Classical sheep transmissible spongiform encephalopathies: pathogenesis, pathological phenotypes and clinical disease. Neuropathol Appl Neurobiol 2007; 33:373-94. [PMID: 17617870 DOI: 10.1111/j.1365-2990.2007.00868.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Scrapie is a prion disease or transmissible spongiform encephalopathy (TSE) of sheep, goats and moufflon. As with its human counterparts, pathology consists of vacuolation, gliosis and accumulations of abnormal forms of a host prion protein (PrPd) in the brain of affected individuals. Immunohistochemical methods can be used to identify both the intracellular truncation sites of PrPd in different cell types (PrPd epitope mapping) and the different morphological patterns of accumulation (PrPd profiling). Differences in the inferred truncation sites of PrPd are found for different strains of sheep TSEs and for different infected cell types within individual strains. Immunochemical methods of characterizing strains broadly correspond to PrPd mapping discriminatory results, but distinct PrPd profiles, which provide strain- and source-specific information on both the cell types which sustain infection (cellular tropisms) and the cellular processing of PrPd, have no immunoblotting counterparts. The cause of neurological dysfunction in human is commonly considered to be neuronal loss secondary to a direct or indirect effect of the accumulation of PrPd. However, in sheep scrapie there is no significant neuronal loss, and relationships between different magnitudes, topographical and cytological forms of PrPd accumulation and clinical signs are not evident. PrPd accumulation also occurs in lymphoid tissues, for which there is indirect evidence of a pathological effect, in the peripheral nervous system and in other tissues. It is generally assumed that neuroinvasion results from infection of the enteric nervous system neurones subsequent to amplification of infectivity in lymphoid tissues and later spread via sympathetic and parasympathetic pathways. The evidence for this is, however, circumstantial. Accumulation of PrPd and presence of infectivity in tissues other than the nervous and lymphoreticular systems gives insights on the ways of transmission of infection and on food safety.
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Affiliation(s)
- M Jeffrey
- Veterinary Laboratory Agency, Lasswade Laboratory, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, Scotland, UK.
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61
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Owen JP, Rees HC, Maddison BC, Terry LA, Thorne L, Jackman R, Whitelam GC, Gough KC. Molecular profiling of ovine prion diseases by using thermolysin-resistant PrPSc and endogenous C2 PrP fragments. J Virol 2007; 81:10532-9. [PMID: 17652380 PMCID: PMC2045483 DOI: 10.1128/jvi.00640-07] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Disease-associated PrP fragments produced upon in vitro or in vivo proteolysis can provide significant insight into the causal strain of prion disease. Here we describe a novel molecular strain typing assay that used thermolysin digestion of caudal medulla samples to produce PrPres signatures on Western blots that readily distinguished experimental sheep bovine spongiform encephalopathy (BSE) from classical scrapie. Furthermore, the accumulation of such PrPres species within the cerebellum also appeared to be dependent upon the transmissible spongiform encephalopathy (TSE) strain, allowing discrimination between two experimental strains of scrapie and grouping of natural scrapie isolates into two profiles. The occurrence of endogenously produced PrP fragments, namely, glycosylated and unglycosylated C2, within different central nervous system (CNS) regions is also described; this is the first detailed description of such scrapie-associated fragments within a natural host. The advent of C2 fragments within defined CNS regions, compared between BSE and scrapie cases and also between two experimental scrapie strains, appeared to be largely dependent upon the TSE strain. The combined analyses of C2 fragments and thermolysin-resistant PrP species within caudal medulla, cerebellum, and spinal cord samples allowed natural scrapie isolates to be separated into four distinct molecular profiles: most isolates produced C2 and PrPres in all CNS regions, a second group lacked detectable cerebellar C2 fragments, one isolate lacked both cerebellar PrPres and C2, and a further isolate lacked detectable C2 within all three CNS regions and also lacked cerebellar PrPres. This CNS region-specific deposition of disease-associated PrP species may reflect the natural heterogeneity of scrapie strains in the sheep population in the United Kingdom.
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Affiliation(s)
- Jonathan P Owen
- ADAS UK, Department of Biology, Adrian Building, University of Leicester, University Road, Leicester LE1 7RH, Leicestershire, United Kingdom
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62
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Tongue SC, Wilesmith JW, Nash J, Kossaibati M, Ryan J. The importance of the PrP genotype in active surveillance for ovine scrapie. Epidemiol Infect 2007; 136:703-12. [PMID: 17588284 PMCID: PMC2870848 DOI: 10.1017/s0950268807008928] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Surveillance activities for ovine scrapie have expanded in the 21st century, following concerns about the potential for a hidden epidemic of bovine spongiform encephalopathy in European sheep populations. Large-scale surveys have been used to estimate the prevalence of scrapie infection. In this study we analyse data from the surveys in Great Britain between 2002 and 2004. When we estimate genotype-specific prevalences for each of the two screening tests used a difference is observed. One test underestimates the number of positive cases in genotypes classically considered to be at a low relative risk of developing clinical disease (ARR- and AHQ-containing genotypes). By comparison, the other test underestimates the number of positive cases in genotypes classically considered to be at an increased relative risk of developing clinical disease (VRQ-containing genotypes). These findings have implications for surveillance, disease control, and diagnostic test evaluation.
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Affiliation(s)
- S C Tongue
- Centre for Epidemiology and Risk Analysis, Veterinary Laboratories Agency, Weybridge, Surrey, UK.
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63
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Hunter N. Scrapie: uncertainties, biology and molecular approaches. Biochim Biophys Acta Mol Basis Dis 2007; 1772:619-28. [PMID: 17560089 DOI: 10.1016/j.bbadis.2007.04.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Revised: 04/23/2007] [Accepted: 04/26/2007] [Indexed: 10/23/2022]
Abstract
The study of the biology of scrapie in sheep is irretrievably associated with the genetics of the PrP gene in sheep. Control of susceptibility and resistance is so closely linked to certain alleles of the sheep PrP gene that no review on scrapie can avoid PrP genetics. Before the importance of PrP protein was discovered and before the influence of the gene itself on disease incidence was understood, it was clear there were some sheep which were more susceptible to natural scrapie than others and that this feature was heritable. These early observations have led to the development and use of PrP genotyping in sheep in what is probably the biggest genetic selection process ever attempted. The accompanying increase in surveillance has also discovered a novel type of scrapie, the subject of much speculation about its origin.
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Affiliation(s)
- Nora Hunter
- Neuropathogenesis Unit, Roslin Institute, West Mains Road, Edinburgh, Scotland, UK.
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64
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Arsac JN, Andreoletti O, Bilheude JM, Lacroux C, Benestad SL, Baron T. Similar biochemical signatures and prion protein genotypes in atypical scrapie and Nor98 cases, France and Norway. Emerg Infect Dis 2007; 13:58-65. [PMID: 17370516 PMCID: PMC2725815 DOI: 10.3201/eid1301.060393] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Similarities raise questions regarding the origin of these recently described cases. Isolates of atypical scrapie recently identified in sheep and goats in France were compared with Nor98 isolates reported in Norway. Western blot methods for characterization of the protease-resistant prion protein showed that all these isolates shared a unique biochemical signature: 5 groups of bands, including a characteristic band of apparent low molecular weight (11 kDa). This pattern could originate from the presence of 3 different protease cleavage products, including the 11 kDa most likely cleaved at both N- and C-sides of the protein. Genetic data, which strongly suggested the higher susceptibility of AHQ and AF141RQ animals in French cases, resembled earlier data from Nor98 scrapie.
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Affiliation(s)
- Jean-Noël Arsac
- Agence Française de Sécurité Sanitaire des Aliments, Lyon, France
| | | | | | | | | | - Thierry Baron
- Agence Française de Sécurité Sanitaire des Aliments, Lyon, France
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65
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Moreno CR, Moazami-Goudarzi K, Laurent P, Cazeau G, Andreoletti O, Chadi S, Elsen JM, Calavas D. Which PrP haplotypes in a French sheep population are the most susceptible to atypical scrapie? Arch Virol 2007; 152:1229-32. [PMID: 17426916 DOI: 10.1007/s00705-007-0956-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Accepted: 02/07/2007] [Indexed: 10/23/2022]
Abstract
A French sheep case control study has been organised to estimate the effects of the PrP haplotypes on resistance to atypical scrapie. The ALHQ and AFRQ haplotypes are significantly more susceptible than the others.
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Affiliation(s)
- C R Moreno
- INRA - Institut National Recherche Agronomique, Stadion d'Amelioration Genetique des Animaux, Castanet-Tolosan, France.
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66
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Opinion of the Scientific Panel on biological hazards (BIOHAZ) on certain aspects related to the risk of Transmissible Spongiform Encephalopathies (TSEs) in ovine and caprine animals. EFSA J 2007. [DOI: 10.2903/j.efsa.2007.466] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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67
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Konold T, Davis A, Bone G, Bracegirdle J, Everitt S, Chaplin M, Saunders GC, Cawthraw S, Simmons MM. Clinical findings in two cases of atypical scrapie in sheep: a case report. BMC Vet Res 2007; 3:2. [PMID: 17298670 PMCID: PMC1810526 DOI: 10.1186/1746-6148-3-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2006] [Accepted: 02/13/2007] [Indexed: 12/03/2022] Open
Abstract
Background Atypical scrapie is a recently recognised form of transmissible spongiform encephalopathy of sheep that differs from classical scrapie in its neuropathological and biochemical features. Most cases are detected in apparently healthy sheep and information on the clinical presentation is limited. Case presentation This report describes the clinical findings in two sheep notified as scrapie suspects and confirmed as atypical scrapie cases by immunohistochemistry and Western immunoblotting. Although both sheep displayed signs suggestive of a cerebellar dysfunction there was considerable variation in the individual clinical signs, which were similar to classical scrapie. Conclusion Any sheep presenting with neurological gait deficits should be assessed more closely for other behavioural, neurological and physical signs associated with scrapie and their presence should lead to the suspicion of scrapie.
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Affiliation(s)
- Timm Konold
- Neuropathology, Veterinary Laboratories Agency Weybridge, New Haw, Addlestone, UK
- Royal Veterinary College, Population Biology and Disease Control Research Group, North Mymms, Hatfield, UK
| | - Andrew Davis
- Neuropathology, Veterinary Laboratories Agency Weybridge, New Haw, Addlestone, UK
| | - Gemma Bone
- Neuropathology, Veterinary Laboratories Agency Weybridge, New Haw, Addlestone, UK
| | | | - Sharon Everitt
- TSE Molecular Biology 4, Veterinary Laboratories Agency Weybridge, New Haw, Addlestone, UK
| | - Melanie Chaplin
- TSE Molecular Biology 4, Veterinary Laboratories Agency Weybridge, New Haw, Addlestone, UK
| | - Ginny C Saunders
- TSE Molecular Biology 4, Veterinary Laboratories Agency Weybridge, New Haw, Addlestone, UK
| | - Saira Cawthraw
- TSE Molecular Biology 4, Veterinary Laboratories Agency Weybridge, New Haw, Addlestone, UK
| | - Marion M Simmons
- Neuropathology, Veterinary Laboratories Agency Weybridge, New Haw, Addlestone, UK
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68
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Thackray A, Hopkins L, Bujdoso R. Proteinase K-sensitive disease-associated ovine prion protein revealed by conformation-dependent immunoassay. Biochem J 2007; 401:475-83. [PMID: 17018021 PMCID: PMC1820801 DOI: 10.1042/bj20061264] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PrPSc [abnormal disease-specific conformation of PrP (prion-related protein)] accumulates in prion-affected individuals in the form of amorphous aggregates. Limited proteolysis of PrPSc results in a protease-resistant core of PrPSc of molecular mass of 27-30 kDa (PrP27-30). Aggregated forms of PrP co-purify with prion infectivity, although infectivity does not always correlate with the presence of PrP27-30. This suggests that discrimination between PrPC (normal cellular PrP) and PrPSc by proteolysis may underestimate the repertoire and quantity of PrPSc subtypes. We have developed a CDI (conformation-dependent immunoassay) utilizing time-resolved fluorescence to study the conformers of disease-associated PrP in natural cases of sheep scrapie, without using PK (proteinase K) treatment to discriminate between PrPC and PrPSc. The capture-detector CDI utilizes N-terminal- and C-terminal-specific anti-PrP monoclonal antibodies that recognize regions of the prion protein differentially buried or exposed depending on the extent of denaturation of the molecule. PrPSc was precipitated from scrapie-infected brain stem and cerebellum tissue following sarkosyl extraction, with or without the use of sodium phosphotungstic acid, and native and denatured PrPSc detected by CDI. PrPSc was detectable in brain tissue from homozygous VRQ (V136 R154 Q171) and ARQ (A136 R154 Q171) scrapie-infected sheep brains. The highest levels of PrPSc were found in homozygous VRQ scrapie-infected brains. The quantity of PrPSc was significantly reduced, up to 90% in some cases, when samples were treated with PK prior to the CDI. Collectively, our results show that the level of PrPSc in brain samples from cases of natural scrapie display genotypic differences and that a significant amount of this material is PK-sensitive.
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Affiliation(s)
- Alana M. Thackray
- Centre for Veterinary Science, Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 OES, U.K
| | - Lee Hopkins
- Centre for Veterinary Science, Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 OES, U.K
| | - Raymond Bujdoso
- Centre for Veterinary Science, Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 OES, U.K
- To whom correspondence should be addressed (email )
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69
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Lehto MT, Peery HE, Cashman NR. Current and future molecular diagnostics for prion diseases. Expert Rev Mol Diagn 2006; 6:597-611. [PMID: 16824033 DOI: 10.1586/14737159.6.4.597] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
It is now widely held that the infectious agents underlying the transmissible spongiform encephalopathies are prions, which are primarily composed of a misfolded, protease-resistant isoform of the host prion protein. Untreatable prion disorders include some human diseases, such as Creutzfeldt-Jakob disease, and diseases of economically important animals, such as bovine spongiform encephalopathy (cattle) and chronic wasting disease (deer and elk). Detection and diagnosis of prion disease (and presymptomatic incubation) is contingent upon developing novel assays, which exploit properties uniquely possessed by this misfolded protein complex, rather than targeting an agent-specific nucleic acid. This review highlights some of the conventional and disruptive technologies developed to respond to this challenge.
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Affiliation(s)
- Marty T Lehto
- Amorfix Life Sciences, 3080 Yonge Street, Suite 6020, Toronto, M4N 3N1, Canada.
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70
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Saunders GC, Cawthraw S, Mountjoy SJ, Hope J, Windl O. PrP genotypes of atypical scrapie cases in Great Britain. J Gen Virol 2006; 87:3141-3149. [PMID: 17030846 DOI: 10.1099/vir.0.81779-0] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Great Britain and elsewhere have detected atypical scrapie infection in sheep with PrP genotypes thought to be genetically resistant to the classical form of scrapie. DNA sequencing of the PrP gene of British atypical scrapie cases (n=69), classical scrapie cases (n=59) and scrapie-free controls (n=138) was undertaken to identify whether PrP variants, other than the three well-characterized polymorphic codons, influenced susceptibility to atypical scrapie infection. Four non-synonymous changes, M112T, M137T, L141F and P241S, were detected that are most probably associated with the A(136)R(154)Q(171) haplotype. Only the PrP variant containing a phenylalanine residue at amino acid position 141 was found to be associated more commonly with the atypical scrapie cases. In addition to the single nucleotide polymorphisms associated with the ARQ allele, two out of nine atypical scrapie cases with the ARR/ARR genotype were found to contain a 24 bp insertion, leading to an additional octapeptide repeat. In terms of PrP genetics, one classification of the GB scrapie cases examined in this study would place animals carrying any homozygous or heterozygous combination of ARR, AHQ or AF(141)RQ alleles, or any one of these alleles when paired with ARQ, as being susceptible to atypical scrapie infection, and animals heterozygous or homozygous for VRQ or homozygous for ARQ as being susceptible to classical scrapie disease. The AHQ PrP allele was associated with the highest incidence of atypical scrapie (263 per 100 000 alleles), whilst VRQ was associated with the lowest incidence (10 per 100 000 alleles).
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Affiliation(s)
- G C Saunders
- Department of TSE Molecular Biology, Veterinary Laboratories Agency, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - S Cawthraw
- Department of TSE Molecular Biology, Veterinary Laboratories Agency, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - S J Mountjoy
- Department of TSE Molecular Biology, Veterinary Laboratories Agency, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - J Hope
- Department of TSE Molecular Biology, Veterinary Laboratories Agency, New Haw, Addlestone, Surrey KT15 3NB, UK
| | - O Windl
- Department of TSE Molecular Biology, Veterinary Laboratories Agency, New Haw, Addlestone, Surrey KT15 3NB, UK
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71
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Baron T, Biacabe AG, Arsac JN, Benestad S, Groschup MH. Atypical transmissible spongiform encephalopathies (TSEs) in ruminants. Vaccine 2006; 25:5625-30. [PMID: 17126958 DOI: 10.1016/j.vaccine.2006.10.058] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Accepted: 10/30/2006] [Indexed: 11/22/2022]
Abstract
Transmissible spongiform encephalopathies (TSEs) are associated with the accumulation in infected tissues of a disease-associated form of a host-encoded protein, the prion protein (PrP). Contrary to the normal form of the protein, this form of PrP is partially resistant to protease digestion (PrP(res)). Detailed characterisation of PrP(res) has been intensively investigated in recent years to try and decipher the diversity of TSEs in human and animals. This considerably and unexpectedly enlarged our knowledge about such diseases in ruminants. Previously, such a diversity was essentially shown by the demonstration that scrapie from sheep and goats could have different biological behaviours following transmission of the disease in mice, unlike bovine spongiform encephalopathy from cattle (BSE) which showed a distinct and unique behaviour. The properties of the BSE agent were also demonstrated to be very stable, following transmission to a variety of different species. Molecular studies of PrP(res), followed by transmission studies to mice, gave the first evidence for the accidental transmission of the BSE agent to humans where it induced a variant form of the fatal Creutzfeldt-Jakob disease (CJD) and also to different animal species including a goat in France. This last case was found among a few unusual cases of TSEs in small ruminants that showed some molecular similarities with BSE and which are currently under investigation by transmission studies in mice. The application of the molecular methods to characterise PrP(res) has most recently led to the unexpected discovery of deviant BSE forms in a few affected cattle in Europe and in the United States, which raises the question of a possible different origin at least of some cases of BSE in cattle. Finally, considerable numbers of a new TSE form in small ruminants, referred to as "atypical scrapie" or "Nor98", have meanwhile been identified in most European countries by TSE rapid testing using an assay which recognizes also comparatively less PK resistant PrP(res).
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Affiliation(s)
- T Baron
- AFSSA-Lyon, Unité ATNC, Lyon, France.
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Opinion of the Scientific Panel on biological hazards (BIOHAZ) on classification of atypical Transmissible Spongiform Encephalopathy (TSE) cases in Small Ruminants. EFSA J 2005. [DOI: 10.2903/j.efsa.2005.276] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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