title: Myelin vacuolation, optic neuropathy and retinal degeneration after closantel overdosage in sheep and in a goat.
abstract: Toxicity of closantel, a halogenated salicylanilide anthelmintic, is described in 11 sheep and a goat, humanely killed 4-70 days after accidental overdosage. Status spongiosis of the cerebrum and cerebellum was present, its severity decreasing with time after treatment. Ultrastructurally, vacuoles in the cerebral white matter were seen to be intramyelinic due to splitting of myelin lamellae at the intraperiod lines, indicating myelin oedema. In the optic nerves, Wallerian degeneration and eventual fibrosis and atrophy of the nerves followed myelin vacuolation. Lesions in the optic nerves were particularly advanced in the intracanalicular portion, indicating a compressive neuropathy within the optic canal. Acute retinal lesions consisted of papilloedema, necrosis of the outer retinal layers (especially the photoreceptor layer), and retinal separation in tapetal and non-tapetal areas. In more chronic cases, the outer nuclear layer was diffusely attenuated and generally reduced to a single row of cells.
authors.affiliation: Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag X05, 0110 Onderstepoort, South Africa. j.vanderlugt@vet.uu.nl
authors.forename: J J
authors.initials: JJ
authors.lastname: van der Lugt
authors.forename: I
authors.initials: I
authors.lastname: Venter
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000506:poisoning*; D002531:Cerebellum / Q000187:drug effects / Q000473:pathology; D062787:Drug Overdose / Q000662:veterinary; D015511:Goat Diseases / Q000139:chemically induced* / Q000473:pathology; D006041:Goats; D046529:Microscopy, Electron, Transmission / Q000662:veterinary; D009186:Myelin Sheath / Q000648:ultrastructure*; D009901:Optic Nerve Diseases / Q000139:chemically induced / Q000473:pathology / Q000662:veterinary*; D012162:Retinal Degeneration / Q000139:chemically induced / Q000473:pathology / Q000662:veterinary*; D012458:Salicylanilides / Q000506:poisoning*; D012756:Sheep; D012757:Sheep Diseases / Q000139:chemically induced* / Q000473:pathology; D013687:Telencephalon / Q000187:drug effects / Q000473:pathology; D014617:Vacuoles / Q000648:ultrastructure*
chemical_list: D000871:Anthelmintics; D012458:Salicylanilides; C023342:closantel