Production Animal Clinical Toxicology

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

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Plants

Nerium oleander - oleander

Thevetia peruviana - Cook tree or yellow oleander

Homeria spp. - Cape tulips

Asclepias spp. - cotton bushes or milkweeds

Epidemiology

• generally plants unpalatable
• accidental ingestion of cuttings in grass clippings
• cape tulips
• may be baled in hay
• may be ingested if stock unfamiliar as animals learn to avoid
• may be ingested if stock starving
• lethal dose of oleander for large animals - about 30g

Pathogenesis

• compounds include digoxin, digitoxin and ouabain
• inhibit cardiac Na/K ATPase involved in sodium pump and hence membrane potential leading to persistent or frequent depolarisation
• increases force of systole
• also act on vagus nerve to decrease heart rate
• have a gastrointestinal irritant effect

Clinical Signs

• reflect effect of toxins on CNS, myocardium, g.i.t.
• sudden death
• salivation, vomiting
• muscular tremors
• irregularity in respiration and heart rate
• struggling and convulsions
• coma and death
• illness prolonged - diarrhoea or constipation, gassy bloat from ruminal stasis

Clinical Pathology

• nonspecific

Necropsy

• gastroenteritis especially of abomasum and duodenum
• myocardial congestion and haemorrhage; histological focal myocardial necrosis
• hepatic congestion

Diagnosis

• history

Treatment

• subacute cases may respond to atropine to reduce vagal tone followed by propanol to prevent tachycardia and arrhythmias