Intravenous Spectinomycin-Associated Deaths in Feedlot Cattle

Abstract

The Veterinary Diagnostic Laboratories at South Dakota State University and Iowa State University were presented with 10 cases in which acute deaths occurred in stressed feedlot cattle following intravenous (IV) administration of the oral water-soluble form of the antibiotic spectinomycin. Within 0.5 hours of IV administration, 40-60% of the treated cattle developed clinical signs of respiratory distress followed by weakness, collapse, and death. Extensive pulmonary edema with marked fluid distension of interlobular septa was the most prominent gross necropsy finding. Histopathologic examination revealed pulmonary edema and fibrinous thrombi in capillaries of multiple organs, suggestive of endotoxemia. In fall 1992, the Animal Disease Research and Diagnostic Laboratory at South Dakota State University received 3 different cases that could be traced to the IV use of spectinomycin. In the case involving the most calves (11 dead out of 13 treated), the calves were from a group of 60 that weighed approximately 250 kg each, originated in Oregon, and developed respiratory problems at a livestock auction. They were removed from sale by the attending veterinarian, who decided to use spectinomycin a as the antimicrobial treatment. The same treatment regimen (5 cc/45 kg of a 100 mg/ ml self-manufactured spectinomycin solution) had been used by him for several years with no known adverse reactions. Prior to treatment, the calves had fevers of 106-108 F and showed signs of respiratory disease but no mouth breathing. The treatment was given at 5 PM, and within a short time the affected calves developed clinical signs of respiratory distress followed by weakness, collapse, and death. By next morning, 11 of the 13 calves were dead. Three of these calves were presented for necropsy. Gross examination findings consisted of cranioventral consolidation involving approximately 15-20% of at least 1 lung field of all 3 calves. The other most obvious gross lesion was the extensive pulmonary edema with marked distention of the interlobular septa by gelatinous edematous fluid (Fig. 1). Microscopic findings in the consolidated portion of the lungs consisted of fibrinopurule nt bronchopneumo nia. Some of the lobules were necrotic. In the nonconsolidated portions, the predominant changes were pulmonary edema and con