Helichrysum argyrosphaerum

Abstract

DISTRIBUTION: • It occurs in sandy areas – often a weed in disturbed places • Widespread

BOTANICAL 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.