title: Case-control study on the use of pituitary-derived hormones from sheep as a potential risk factor for the occurrence of atypical scrapie in Great Britain.
abstract: A case-control study was conducted in 2013 to investigate the use of pituitary-derived hormones from sheep as a potential risk factor for the presence of atypical scrapie in Great Britain sheep holdings. One hundred and sixty-five holdings were identified as cases. Two equal sets of controls were selected: no case of scrapie and cases of classical scrapie. A total of 495 holdings were selected for the questionnaire survey, 201 responses were received and 190 (38.3 per cent) were suitable for analysis. The variables 'use-of-heat-synchronisation/superovulation' and 'flock size' were significantly associated with the occurrence of atypical scrapie. Farms with atypical cases were less likely (OR 0.25, 95 per cent CI 0.07 to 0.89) to implement heat synchronisation/superovulation in the flock than the control group. Atypical cases were 3.3 times (95 per cent CI 1.38 to 8.13) more likely to occur in large holdings (>879 sheep) than in small flocks (<164 sheep). If the 'use-of-heat-synchronisation/superovulation' is a proxy for the use of pituitary-derived hormones, the significant negative association between having a case of atypical scrapie and the use of these practices rules out the initial hypothesis that using these drugs is a risk factor for the occurrence of atypical scrapie. Flock size was a significant risk factor for atypical scrapie, consistent with a previous generic case-control study.
authors.affiliation: Department of Epidemiological Sciences (DES), Animal Health and Veterinary Laboratories Agency - Weybridge, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors.forename: E
authors.identifier: http://orcid.org/0000-0003-0187-3906
authors.initials: E
authors.lastname: Marier
authors.affiliation: Department of Pathology, Animal Health and Veterinary Laboratories Agency - Weybridge, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors.forename: M
authors.initials: M
authors.lastname: Dawson
authors.affiliation: Department of Virology, Animal Health and Veterinary Laboratories Agency - Weybridge, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors.forename: M
authors.initials: M
authors.lastname: Simmons
authors.affiliation: Department of Pathology, Animal Health and Veterinary Laboratories Agency - Weybridge, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors.forename: J
authors.initials: J
authors.lastname: Hope
authors.affiliation: Department of Epidemiological Sciences (DES), Animal Health and Veterinary Laboratories Agency - Weybridge, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors.forename: A
authors.initials: A
authors.lastname: Ortiz-Peláez
mesh_terms: D000818:Animals; D016022:Case-Control Studies; D010907:Pituitary Hormones / Q000009:adverse effects*; D012307:Risk Factors; D012608:Scrapie / Q000453:epidemiology*; D012756:Sheep; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D010907:Pituitary Hormones
keywords: Atypical scrapie; Risks factors; Sheep; pituitary