Helichrysum argyrosphaerum

Abstract

DISTRIBUTION: • It occurs in sandy areas – often a weed in disturbed places • WidespreadBOTANICAL DESCRIPTION: General: An annual herb with radiating, flat, woolly stems growing flat on the ground like a mat, up to 150 mm high. Leaves: Leaves are spoon - shaped and hairy Flowers: Flower heads are characteristic - round like a ball with transparent bracts of which the outer rows are shiny silvery and the centre rows are pink, turning white and papery with age. Fertile flowers have yellow centres.TOXIC PRINCIPLE: Unknown neurotoxin causing chronic encephalopathy when eaten in large quantities.SYSTEMS AFFECTED: Central nervous system.CLINICAL SIGNS: • Problem in sheep and to lesser extent cattle, especially in luxuriantly flowering stage of the plant. • Blindness. Amaurosis (blindness without apparent lesion of the eye), mydriasis, stargazing, cataracts (seen few months later in some cases). • Paresis, paralysis - sometimes circling movements. • CNS depression. • Animals don’t die, but can’t feed or drink and must be destroyed. • Permanent brain damage - prognosis extremely poor (depending on where lesions are).NECROPSY: Macroscopical findings: • Post mortem rather negative. • Brain oedema.HISTOPATHOLOGY: • Bilateral status spongiosus of the fasciculus, optic chiasm, (especially in blind cases), white matter of brain, spinal cord and even nerves. • Retinal necrosis seen as well. • Degeneration and necrosis of muscle fibres.