Pavetta species

Abstract

DISTRIBUTION: • P. schumanniana occurs mainly in the high rainfall areas and in sour bushveld, showing a preference for sour, stony veld or mountain slopes. • Usually in the open, but also found among bushes and under trees. • P harborii prefers deep sandy soils.

BOTANICAL DESCRIPTION: Pavetta schumanniana General: A much-branched shrub or tree up to 4 m high. Leaves: Usually opposite, but often whorled with triangular stipules between them, large, broadest towards the tip. They have a rough leathery texture and are finely and densely hairy below. Venation is raised on the underside. Round dark bacterial nodules scattered throughout the leaf surface. Deciduous. Flowers: Dense white fragrant clusters. The calyx lobes are toothed, with sharp tips. Styles protruding. Summer. Fruit: Round and fleshy, ± 8 mm in diameter. First green, changing to glossy black when mature

Pavetta harborii General: A perennial shrublet with short greyish to yellowish aerial stems sprouting from underground roots over a large area - could be up to 2 m in diameter. Leaves: Deciduous, opposite. Sparsely hairy above and paler, felt-like underneath. Round dark bacterial nodules scattered through-out the leaf surface. Flowers: Dense white fragrant clusters of tubular flowers. Early summer. Fruit: Small, round and fleshy. First green, changing to glossy black when mature

TOXIC PRINCIPLE: • A water-soluble polyamine called pavettamine. • Has a delayed effect on the heart. • This toxin is pH-labile and will be destroyed at pH < 2,5. • This could explain why only ruminants are susceptible. (Rumen pH = 6,8). Mechanism of action: The toxin inhibits synthesis of new myocardial protein, especially myosin.

SYNDROME: Gousiekte

SYSTEMS AFFECTED: Cardiovascular system.

CLINICAL SIGNS: After ingestion of a lethal dose of the plants, a characteristic latent period of 6 - 8 weeks of apparent normality follows before the animals suddenly die. The majority of animals typically drop dead, usually after being frightened, handled or chased, although some may die without any stressful event occurring. In a few cases congestive heart failure such as • weakness • panting • respiratory distress and • anasarca, particularly of the head, are present.

NECROPSY: Signs of heart failure: • Lung oedema • Hydrothorax • Hydropericardium Irregular areas of pallor (greyish areas) may be seen, particularly in the endocardium. Although some cases may not show any macroscopic changes.

HISTOPATHOLOGY: • A multifocal to diffuse subendocardial replacement fibrosis accompanied by a round cell infiltration, predominantly in the apex, left ventricular wall and interventricular septum. • Focal to diffuse degeneration and/or necrosis of myofibres. • Hypertrophy or even atrophy of myocardial fibres.

TREATMENT: No specific treatment, only symptomatic and supportive.Avoid unnecessary stressful situations.