Production Animal Clinical Toxicology

Plants | Epidemiology | Pathogenesis | Clinical Signs | Clinical Pathology | Necropsy | Diagnosis | Treatment | Control

Return to Production Animal Clinical Toxicology Index

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Plants

• Pteridium esculentum - common bracken
• Pteridium revolutum - hairy bracken - toxicity uncertain
• Pteridium yarrabense - northern bracken - toxicity uncertain

Epidemiology

animal factors

• ruminants more affected than other species
• cattle more than sheep, but may be that cattle more frequently exposed to plant

plant/environmental factors

• some suggestion that younger fronds more toxic
• variation of carcinogen concentration is primarily due to plant genotype and not other factors

Pathogenesis

• plants can have up to 4 toxins
• radiomimetic factor that induces bone marrow suppression resulting in panleucopaenia, anaemia; thrombocytopaenia and haemorrhage; may also have carcinogenic role
• ptaquiloside, a carcinogen responsible for gastro-intestinal and urinary bladder tumours (enzootic haematuria)
• thiaminase that has primary effect on horses and pigs
• cyanogenetic glycoside of minor significance

Clinical Signs

a. panleucopaenia

• most frequently in calves; adults occasionally; reported in sheep
• up to 3 weeks grazing before onset of symptoms
• seromucoid discharge blood tinged
• diarrhoea; blood in faeces
• haematuria
• haemorrhagic diathesis; haemorrhage into visible mucous membranes
• pyrexia, depression
• nonresponsive to treatment
• death frequently from fibrinous pleuropneumonia

b. enzootic haematuria

• associated with long term consumption from 10 months to 3 yrs
• small amounts of frequent haematuria leading to anaemia

Clinical Pathology

a. panleucopaenia

• anaemia
• leucopaenia
• thrombocytopaenia

b. enzootic haematuria

• anaemia

Necropsy

a. panleucopaenia

• multiple haemorrhages into all tissues

b. enzootic haematuria

• dysplastic to angiomatous or carcinomatous bladder mucosa
• some cattle in some areas may also have alimentary carcinoma

Diagnosis

• history
• clinical pathology
• necropsy

Treatment

• none

Control

• pastures/grazing management