title: The clinical neurology of scrapie in Irish sheep.
abstract: One hundred twenty-nine sheep with scrapie were identified from 20 flocks in which scrapie previously had been confirmed. Physical and neurologic examinations were performed on all animals. Videotape recordings were made and reviewed to assess gait. These procedures were repeated in 46 sheep at 2- to 3-week intervals until recumbency or inappetence necessitated euthanasia. Confirmation of scrapie was made by histopathologic and immunohistochemical examinations of brain tissue. The clinical signs most frequently recorded in the 129 animals on initial presentation were hindlimb ataxia (71%), head tremor (61%), altered mental status (57%), positive nibble reflex (51%), crouching posture (51%), teeth grinding (44%), low head carriage (38%), body condition score (BCS) < 1.5 (38%), and conscious proprioceptive deficits of the hindlimbs (36%). Progression of the disease was characterized by an increase in the frequency and severity of ataxia, weakness and hypermetria of the hindlimbs, a decreasing sway response, a decreasing extensor response to thoracolumbar pressure, and a reduction in the BCS. No effect of farm of origin on the clinical presentation could be shown. The presence of a nibble reflex was strongly associated (P < .0005) with prion protein (PrP) genotypes AA136RR154QH171 and AA136RR154QQ171. Logistic regression modeling of groups with associated clinical signs showed that animals with a crouching posture (odds ratio [OR], 20.036) and an abnormal yield to thoracolumbar pressure (OR, 7.117) were at increased risk of ataxia. Pruritus (OR, 0.168) was negatively associated with ataxia. Pruritus (OR, 4.974) and teeth grinding (OR, 4.279) were associated with a positive nibble reflex.
authors.affiliation: Department of Large Animal Clinical Studies Faculty of Veterinary Medicine, University College Dublin, Belfield, Dublin, Ireland. anne.healy@ucd.ie
authors.forename: Anne M
authors.initials: AM
authors.lastname: Healy
authors.forename: Edwin
authors.initials: E
authors.lastname: Weavers
authors.forename: Maire
authors.initials: M
authors.lastname: McElroy
authors.forename: Mercedes
authors.initials: M
authors.lastname: Gomez-Parada
authors.forename: J Dan
authors.initials: JD
authors.lastname: Collins
authors.forename: Elaine
authors.initials: E
authors.lastname: O'Doherty
authors.forename: Torres
authors.initials: T
authors.lastname: Sweeney
authors.forename: Michael L
authors.initials: ML
authors.lastname: Doherty
mesh_terms: D000818:Animals; D001259:Ataxia / Q000503:physiopathology / Q000662:veterinary; D004247:DNA / Q000737:chemistry / Q000235:genetics; D018450:Disease Progression; D005684:Gait / Q000502:physiology; D007150:Immunohistochemistry / Q000662:veterinary; D016015:Logistic Models; D010291:Paresis / Q000503:physiopathology / Q000662:veterinary; D017354:Point Mutation; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011328:Prions / Q000235:genetics; D011537:Pruritus / Q000503:physiopathology / Q000662:veterinary; D012608:Scrapie / Q000235:genetics / Q000503:physiopathology*; D012756:Sheep; D014743:Videotape Recording
chemical_list: D011328:Prions; D004247:DNA