Introduction

• Cause: ingestion of bluebells.
• Signs: anorexia, depression, signs of abdominal pain, weakness and weak pulse.
• Diagnosis: based on history of exposure and clinical signs.
• Treatment: supportive.
• Prognosis: poor in animals with significant clinical signs.

Pathogenesis

Etiology

• Exposure generally occurs in the spring.
• Exposure could occur through ingestion of contaminated hay, although such cases have not been reported at the time of publication.

Predisposing factors

General

• Access to bluebells.
• Lack of or inability to access other forage.

Pathophysiology

• All parts of these plants contain scillarens, which are cardiac glycosides similar in structure to those of foxglove (Digitalis spp).
• Glycosidase-inhibiting alkaloids have also been described in bluebells and may contribute to the toxic effects.
• The cardiac glycosides found in plants are generally precursors: primary glycosides that undergo enzymatic hydrolysis when plant material is dried or damaged to give the active (or secondary) glycosides.
• Cardiac glycosides also interfere with the cellular membrane sodium-potassium (Na+ -K+ ATPase enzyme system) pump resulting in depletion of intracellular potassium and an increase in serum potassium. This causes irregular heart activity, and eventual complete block of cardiac conduction.
• They also have irritant effects on the gastrointestinal tract.
• Cardiac glycosides can result in cardiac arrhythmias. Dysrhythmias Dysrhythmias including first- and second-degree heart block and ventricular tachycardia. Pulse may be rapid, weak and irregular.

Timecourse

• Limited information in cattle.
• Signs are expected to occur within a few hours with recovery within 1-3 days.

Epidemiology

• Poisoning can occur wherever bluebells grow.
• Cases in cattle are rarely reported.

Diagnosis

Treatment

Prevention

Outcomes