Mounir Brihoum

Descriptive Study of 32 Cases of Doxycycline-Overdosed Calves

BACKGROUND Reports of doxycycline-induced toxicity are limited despite common use of this antibiotic to treat infectious respiratory disorders in calves. OBJECTIVE To describe previously unreported kidney lesions and diagnostic test results in doxycycline-overdosed calves and to compare these results with other findings reported previously. ANIMALS Thirty-two calves that presented with adverse effects after receiving high doses of doxycycline as a treatment for mild respiratory disorders. METHOD Retrospective review of medical records. RESULTS Clinical examination identified mainly lethargy, dyspnea, cough, tongue paresia or paralysis associated with dysphagia and sialorrhea, tachycardia, tachypnea, and signs of myopathy. Blood analysis indicated increases in creatine kinase, lactate dehydrogenase, aspartate aminotransferase, and sorbitol dehydrogenase activities and increased serum creatinine and urea concentrations. ECG recordings and Doppler echocardiography examination identified ventricular premature beats and a decrease in left ventricular global and systolic function, respectively. Necropsy and histopathology disclosed necrosis of the myocardium, tongue, and some striated muscles, acute renal tubular necrosis, and fatty degeneration or congestion of the liver. CONCLUSIONS Most of these findings corroborate previous observations made in doxycycline-overdosed calves, and further suggest myocardial and striated muscular toxicity as well as renal toxicity in doxycycline-overdosed calves.

Clinical evaluation of cardiac effects of experimental doxycycline overdosing in healthy calves

BackgroundCardiac morphologic and functional changes consistent with cardiomyopathy have been reported in field cases of calves with accidental doxycycline overdosing. The purpose of this study was to evaluate clinically the cardiac effects of an experimentally-induced doxycycline overdosing in healthy calves.Twelve 2 months-old healthy Belgian Blue calves were studied. Six of them (group 1) received the normal dose (5 mg/kg, BID) and the six others (group 2) received five times the normal dose (25 mg/kg, BID) of oral doxycycline for five consecutive days (D1 to D5). Each calf was clinically examined daily. Measurement of serum AST, CK, Iso-CKs and LDH activities and an echocardiographic examination were performed before (D0) and one day after (D6) the last doxycycline administration. An ECG tracing was recorded at D0, D4, and D6.ResultsIn both groups, no clinical, blood, echocardiographic or electrocardiographic changes suggestive of a cardiomyopathy were observed. Only a decreased appetite was observed in the calves of the group 2 between D3 and D6.ConclusionsThis trial failed to reproduce cardiac changes reported in accidental doxycycline-poisoning in calves, suggesting that high doses of doxycycline may not be the only etiologic factor of the cardiomyopathy reported in the field cases.