Epidemiological characteristics of classical scrapie outbreaks in 30 sheep flocks in the United Kingdom.
<h4>Background</h4>Most previous analyses of scrapie outbreaks have focused on flocks run by research institutes, which may not reflect the field situation. Within this study, we attempt to rectify this deficit by describing the epidemiological characteristics of 30 sheep flocks naturall...
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Public Library of Science (PLoS)
2008-01-01
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| Series: | PLoS ONE |
| Online Access: | https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0003994&type=printable |
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| author | K Marie McIntyre Simon Gubbins Wilfred Goldmann Nora Hunter Matthew Baylis |
| author_facet | K Marie McIntyre Simon Gubbins Wilfred Goldmann Nora Hunter Matthew Baylis |
| author_sort | K Marie McIntyre |
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| description | <h4>Background</h4>Most previous analyses of scrapie outbreaks have focused on flocks run by research institutes, which may not reflect the field situation. Within this study, we attempt to rectify this deficit by describing the epidemiological characteristics of 30 sheep flocks naturally-infected with classical scrapie, and by exploring possible underlying causes of variation in the characteristics between flocks, including flock-level prion protein (PrP) genotype profile. In total, the study involved PrP genotype data for nearly 8600 animals and over 400 scrapie cases.<h4>Methodology/principal findings</h4>We found that most scrapie cases were restricted to just two PrP genotypes (ARQ/VRQ and VRQ/VRQ), though two flocks had markedly different affected genotypes, despite having similar underlying genotype profiles to other flocks of the same breed; we identified differences amongst flocks in the age of cases of certain PrP genotypes; we found that the age-at-onset of clinical signs depended on peak incidence and flock type; we found evidence that purchasing infected animals is an important means of introducing scrapie to a flock; we found some evidence that flock-level PrP genotype profile and flock size account for variation in outbreak characteristics; identified seasonality in cases associated with lambing time in certain flocks; and we identified one case that was homozygous for phenylalanine at codon 141, a polymorphism associated with a very high risk of atypical scrapie, and 28 cases that were heterozygous at this codon.<h4>Conclusions/significance</h4>This paper presents the largest study to date on commercially-run sheep flocks naturally-infected with classical scrapie, involving 30 study flocks, more than 400 scrapie cases and over 8500 PrP genotypes. We show that some of the observed variation in epidemiological characteristics between farms is related to differences in their PrP genotype profile; although much remains unexplained and may instead be attributed to the stochastic nature of scrapie dynamics. |
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| issn | 1932-6203 |
| language | English |
| publishDate | 2008-01-01 |
| publisher | Public Library of Science (PLoS) |
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| spelling | doaj-art-0e0d1e1af0e94f95be13169c712f8e7e2025-08-20T02:38:29ZengPublic Library of Science (PLoS)PLoS ONE1932-62032008-01-01312e399410.1371/journal.pone.0003994Epidemiological characteristics of classical scrapie outbreaks in 30 sheep flocks in the United Kingdom.K Marie McIntyreSimon GubbinsWilfred GoldmannNora HunterMatthew Baylis<h4>Background</h4>Most previous analyses of scrapie outbreaks have focused on flocks run by research institutes, which may not reflect the field situation. Within this study, we attempt to rectify this deficit by describing the epidemiological characteristics of 30 sheep flocks naturally-infected with classical scrapie, and by exploring possible underlying causes of variation in the characteristics between flocks, including flock-level prion protein (PrP) genotype profile. In total, the study involved PrP genotype data for nearly 8600 animals and over 400 scrapie cases.<h4>Methodology/principal findings</h4>We found that most scrapie cases were restricted to just two PrP genotypes (ARQ/VRQ and VRQ/VRQ), though two flocks had markedly different affected genotypes, despite having similar underlying genotype profiles to other flocks of the same breed; we identified differences amongst flocks in the age of cases of certain PrP genotypes; we found that the age-at-onset of clinical signs depended on peak incidence and flock type; we found evidence that purchasing infected animals is an important means of introducing scrapie to a flock; we found some evidence that flock-level PrP genotype profile and flock size account for variation in outbreak characteristics; identified seasonality in cases associated with lambing time in certain flocks; and we identified one case that was homozygous for phenylalanine at codon 141, a polymorphism associated with a very high risk of atypical scrapie, and 28 cases that were heterozygous at this codon.<h4>Conclusions/significance</h4>This paper presents the largest study to date on commercially-run sheep flocks naturally-infected with classical scrapie, involving 30 study flocks, more than 400 scrapie cases and over 8500 PrP genotypes. We show that some of the observed variation in epidemiological characteristics between farms is related to differences in their PrP genotype profile; although much remains unexplained and may instead be attributed to the stochastic nature of scrapie dynamics.https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0003994&type=printable |
| spellingShingle | K Marie McIntyre Simon Gubbins Wilfred Goldmann Nora Hunter Matthew Baylis Epidemiological characteristics of classical scrapie outbreaks in 30 sheep flocks in the United Kingdom. PLoS ONE |
| title | Epidemiological characteristics of classical scrapie outbreaks in 30 sheep flocks in the United Kingdom. |
| title_full | Epidemiological characteristics of classical scrapie outbreaks in 30 sheep flocks in the United Kingdom. |
| title_fullStr | Epidemiological characteristics of classical scrapie outbreaks in 30 sheep flocks in the United Kingdom. |
| title_full_unstemmed | Epidemiological characteristics of classical scrapie outbreaks in 30 sheep flocks in the United Kingdom. |
| title_short | Epidemiological characteristics of classical scrapie outbreaks in 30 sheep flocks in the United Kingdom. |
| title_sort | epidemiological characteristics of classical scrapie outbreaks in 30 sheep flocks in the united kingdom |
| url | https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0003994&type=printable |
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