Clinical and pathological study of experimentally- induced yew (Taxus baccata) poisoning in sheep

Acute yew (Taxus baccata) intoxication was induced in 7 adult sheep by oral administration of the plant materials at the dose of 2.5g/kg body weight. Blood samples for hematology and serum biochemistry were collected before and after the induced intoxication. Electrocardiography was performed using a base-apex lead. Intoxicated animals displayed lethargy, depression, bradycardia and varying intensity of heart sounds. The ECGs of intoxicated sheep showed a variety of arrhythmias and abnormalities including multifocal ventricular tachycardia, idioventricular and idiojunctinal rhythm and QRS and T widening. Four sheep died within 4-16 hours after yew administration. Significant increase of white blood cells, total neutrophil counts and serum sodium concentration were observed. Post mortem examination and histological evaluation were done with special regards on tissue changes of the myocardium and conduction system. There were hyperemia, focal hemorrhage and multifocal nonsuppurative interstitial myocarditis with mild focal cardiac muscle cell degeneration and necrosis in the affected hearts which appeared more prominent in the right atrium. Histopathological examination of cardiac conduction system also revealed moderate to severe interstitial edema with inflammation of the SA-node, AV-node, the bundle branches and His-bundle in all cases which was most severe in the AV-node and the His-bundle. Oral administration of dried leaves of T. baccata, at the dose of 2.5g/kg can induce acute toxicity, manifested clinically by a variety of cardiac arrhythmia and myocardial lesions including special conduction system in pathology.