Staggers in sheep associated with the ingestion of Tributes terrestris

The history of an unusual locomotory disturbance of sheep is traced from its first recognition in 1937 through to the most recent outbreak in 1981-83. The condition occurred only at certain times and in restricted areas of the central and northern slopes districts of New South Wales. Outbreaks were repeatedly associated with drought periods during which sheep grazed large areas of Tribulus terrestris for many months at a time. Many thousands of sheep were affected, but the prevalence varied greatly between flocks. The course of the disease was characterised by a slowly developing, irreversible, asymmetrical, weakness of the hindlimbs. The clinical signs suggested that a lesion of the thoraco-lumbar spinal cord region was present. The macroscopic and microscopic examination of the nervous and musculoskeletal systems failed to demonstrate abnormalities which would account for the clinical signs. Haematological, biochemical and toxicological test results supported the concept of a neuromuscular disease process being present, but failed to indicate its aetiology.