Acokanthera species

Abstract

Distribution: To be found in a variety of habitats; scrub forest, kloofs, rocky wooded hillsides, riverine and coastal bush, to open woodland, though it prefers the protection of other bush.

Botanical description: General: These are evergreen shrubs or small trees, usually about two to three metres in height but can grow up to five metres. The bark is rough and brown, but the young twigs can often be a rich red in spring. Leaves: The thick leathery leaves are glossy dark green above and paler below with a sharp, hard little tip at the apex. Hairless and sometimes red- or purple-tinged. The petioles are often also reddish. It has thick milky latex. Flowers: Dense showy clusters of sweet-scented tubular white flowers flushed with pink that are about 10mm long. Winter to spring. Fruit: Round to oval berries that are 10 to 15 mm long. Initially they are green, turning bright red and then dark purple at maturity.

Toxic principle: These plants are extremely toxic and contain several cardiac glycosides.

Clinical signs: • Acokanthera poisoning occurs very seldomly. • Sheep, goats, ostriches and humans have died following ingestion of the plants, but cattle are reputedly most often affected. The first symptom is apathy, then restlessness, followed by death, with the heart stopping in asystole.

Necropsy: Macroscopic pathology: • Not specific - rather negative • Subepi- and endocardial haemorrhages• Lung oedema, congestion, emphysema• Ruminal atony and enteritis - even haemorrhagic • Leaves present in rumen

Histopathology: In more chronic cases small foci of degeneration of cardiac musculature are seen occasionally

Treatment: • Activated charcoal. • Dose 2g/kg orally. • Large dose is essential. • Minimize stress to prevent catecholamine release. Additional treatment for valuable animals: 1. Lignocaine. 2. ß-blocking agents. 3. ACP: Tranquillizer (multipotent blocker). 4. Atropine (if AV block is present)

Syndrome: Acute poisoning by cardenolide-containing plants.

Systems affected: Cardiovascular system.