title: Osteoarthritis of the temporo-mandibular joint in free-living Soay sheep on St Kilda.
abstract: Osteoarthritis (OA) is a common degenerative disease of synovial joints with the potential to cause pathology and welfare issues in both domestic and wild ruminants. Previous work has identified OA of the elbow joint in domestic sheep, but the prevalence of OA of the jaw and in particular the temporomandibular joint (TMJ) has not been previously reported. Following up a previous report of a single case of TMJ OA in a free-living population of Soay sheep on St Kilda in the Outer Hebrides, an archive of 2736 jaw bones collected from this population between 1985 and 2010 was surveyed. Evidence of TMJ OA was found in 35 sheep. Of these, 15 cases were unilateral (11 right side, 4 left side) and the remaining 20 were bilateral. TMJ pathology was much more common in females than males: only 3/35 cases were in males, with overall prevalence at 2.3% for females and 0.2% in males. Radiographic examination of TMJ with OA revealed extensive bone re-modelling with osteophytosis, particularly of the condyle of the mandible. There was a highly significant age-dependence in TMJ OA incidence among age classes: 30/35 cases occurred in geriatric sheep (aged 7 years or more; 11.1% prevalence within this age class), four in adults (2-6 years old; 0.9% prevalence), one in yearlings (0.3% prevalence) and none in lambs. The low incidence in males was confounded by sex differences in longevity: while 18% of females sampled died in the geriatric age class, only 2% of males did so. Although the low prevalence of the pathology limited the ability to test its association with other traits, it was possible to examine relationships with reproductive performance measures amongst geriatric females with and without TMJ OA. Although there were trends towards lower fecundity and lower lamb birth weight in the breeding season prior to death, these were not statistically significant.
authors.affiliation: Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, The King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
authors.forename: Colin
authors.initials: C
authors.lastname: Arthur
authors.affiliation: Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, The King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Watt
authors.affiliation: Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, The King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Nussey
authors.affiliation: Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, The King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
authors.forename: Josephine M
authors.initials: JM
authors.lastname: Pemberton
authors.affiliation: Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, The King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
authors.forename: Jill G
authors.initials: JG
authors.lastname: Pilkington
authors.affiliation: Department of Natural Sciences, National Museums Scotland, Chambers Street, Edinburgh EH1 1JF, UK.
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Herman
authors.affiliation: Department of Natural Sciences, National Museums Scotland, Chambers Street, Edinburgh EH1 1JF, UK.
authors.forename: Zena L
authors.initials: ZL
authors.lastname: Timmons
authors.affiliation: Division of Veterinary Clinical Sciences, Royal (Dick) School of Veterinary Studies and Roslin Institute, University of Edinburgh, Easter Bush, Roslin EH25 9RG, UK.
authors.forename: Dylan N
authors.initials: DN
authors.lastname: Clements
authors.affiliation: Division of Veterinary Clinical Sciences, Royal (Dick) School of Veterinary Studies and Roslin Institute, University of Edinburgh, Easter Bush, Roslin EH25 9RG, UK. Electronic address: Philip.r.scott@ed.ac.uk.
authors.forename: Philip R
authors.initials: PR
authors.lastname: Scott
mesh_terms: D000818:Animals; D005260:Female; D062312:Islands / Q000453:epidemiology; D008297:Male; D010003:Osteoarthritis / Q000453:epidemiology / Q000662:veterinary*; D012606:Scotland / Q000453:epidemiology; D012756:Sheep; D012757:Sheep Diseases / Q000453:epidemiology*; D013705:Temporomandibular Joint Disorders / Q000453:epidemiology / Q000473:pathology / Q000662:veterinary*
keywords: Osteoarthritis; Radiography; Sheep; St Kilda; Temporo-mandibular joints