Pteridium aquilinum

Abstract

DISTRIBUTION: It is widespread in South Africa, especially in the high rainfall areas, where it can become an invasive plague.

BOTANICAL DESCRIPTION: General: A perennial fern that grows ±1,5 m high. It spreads quickly by means of branched underground rootstocks. These are covered with thick reddish hairs. Leaves: The young leaves (croziers) are coiled and hairy. As they unfold, they become stiff, leathery and glossy green. Spores: The spores resemble a rusty powder on the underside of the leaf. They are borne submarginally as a continuous line closely following the leaf margin.

TOXIC PRINCIPLE: Croziers, fresh and dried fronds, rhizomes, and even the stems are toxic, though the toxicity varies with different parts of the plant and the stage of growth. Large quantities must be consumed for poisoning to occur. The toxic principles are thiaminase I and a radiomimetic compound, ptaquiloside, which induces aplastic anaemia. Central Nervous System: • Thiamine deficiency: ThiaminaseHaemopoietic System: • Radiomimetic syndrome: Ptaquiloside Systems affected: Central nervous and haemopoietic systems.

CLINICAL SIGNS: Central Nervous System: Horses:Appear sleepy, exhibit laboured breathing, locomotary disturbances, tremors and abnormal stance. Convulsions and opisthotonus may even occur. Cattle: Die from ptaquiloside poisoning before Vit. B1 depletion. Ruminants produce Vit. B1 in the rumen. Sheep: May contract cerebrocortical necrosis (CCN) (also known as polioencephalomalacia) due to this plant. Sheep are resistant to ptaquiloside poisoning. Haemopoietic System: Ptaquiloside: Bone marrow depression leads to: • Aplastic anaemia (a lack of development of cells). • Thrombocytopaenia - Prolonged bleeding time due to defective clotting of blood, increasing capillary fragility and increase in heparin-like substances • Leucopaenia - resulting in bacterial infection and fever. Central Nervous System: No meaningful pathological lesions have been reported with bracken poisoning in horses. Haemopoietic System: Cattle: • Extensive haemorrhage and haematomas throughout body. • Numerous ulcers and free blood in g.i.t.

TREATMENT: To counter thiaminase effect administer 100 - 1000 mg thiamine parenterally. For the bleeding tendency: withdraw from source; stimulate bone marrow - anabolic steroids, erythropoietin; protamine sulphate (100 mg i/v); antibiotics.