Production Animal Clinical Toxicology

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

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Plants

• Hypericum perforatum - St John's wort

Epidemiology

• plant will be eaten if young, or if other feed scarce
• dark-skinned animals not susceptible
• goats considered more resistant
• photosensitivity agent stable and persists in hay and old standing plants

Pathogenesis

• due to hypericin, photosensitising red fluorescing pigment
• present in glands on leaves and flowers
• not detoxified by liver, and is deposited in skin
• primary photosensitisation upon exposure to strong sunlight

Clinical Signs

• will occur within 24 hr of consumption
• signs are those of classical photosensitisation
• no evidence for hepatic disease
• dark-skinned areas not affected
• intense pruritis resulting in severe trauma
• early stages the skin appears sensitive to cold water
• contact results in severe pain

Clinical Pathology

• nonspecific

Necropsy

• nonspecific

Diagnosis

• history
• clinical signs

Treatment

• symptomatic and supportive
• keep affected animals in shade

Control

• pasture improvement
• plant - herbicides
• biological - Chrysomela beetles, followed by pasture improvement