Hematological and pathological observations of chronic furazolidone poisoning in calves

Severe thrombocytopenia in young calves experimentally infected with noncytopathic bovine viral diarrhea virus

Seven calves between 1 week and 2 months of age were infected with a noncytopathic field isolate of bovine viral diarrhea virus (BDV) in order to evaluate the effect of BDV infection on the concentration of circulating platelets in the blood. All calves were determined to be free of BDV and neutralizing antibodies to BDV before infection. Platelet counts were performed on a daily basis over a 30-day period beginning at the time of infection. By 2 weeks postinfection, all calves showed a significant drop in the number of circulating platelets and a marked hyperplasia of megakaryocytes in the bone marrow. In three of the seven calves, thrombocytopenia was severe (less than or equal to 5,000/microliters) for 1 to 6 days. In two of these three animals, extensive petechial and ecchymotic hemorrhages were observed on all mucosal surfaces and on various internal organs during the period of severe thrombocytopenia. BDV was consistently isolated from the platelets during the early phases of the infection, and viral antigen was occasionally detected on platelets by a fluorescent-antibody assay. The results demonstrate that BDV infection is associated with decreases in platelet numbers and suggest that platelets may serve as carriers of circulating virus.

Thrombocytopenia associated with acute bovine virus diarrhea infection in cattle

Thrombocytopenia was observed in 15 of 146 cases of clinically acute bovine viral diarrhea virus (BVDV) infection in adult cattle. Platelet counts ranged from 2,000 to 33,000/microliters. Clinically, a bleeding tendency was manifested by bloody diarrhea, petechial and ecchymotic hemorrhage, epistaxis, and abnormal bleeding from injection sites. Coagulation testing (six cases) gave no evidence of disseminated intravascular coagulation. Bone marrow aspirates were suggestive of active marrow necrosis (two cases) or recent repopulation (three cases). Treatment, when given, was supportive and empirical in nature. Six animals experienced complete clinical recoveries; the others died or were euthanatized. Although the pathogenesis of the thrombocytopenia was not definitively determined, thrombocytopenia associated with acute BVDV infection should be considered in the differential diagnosis for cattle with bleeding disorders.

The effect of furazolidone on some clinical and biochemical parameters in goats

Furazolidone (FZ) administered to goats orally at the recommended therapeutic dose (10 mg/kg body weight for 5 days) resulted in significant decreases in heart rate, pulse rate, and rectal temperature. No change was observed in respiratory rate or body weight, although a tendency towards a decrease in the latter was observed. An increase in the number of the erythrocytes was found. FZ also produced significant decreases in the pseudocholinesterase activity and plasma concentrations of total protein and ascorbic acid. A significant increase in the adrenal cholesterol concentration was observed while the weight of adrenal glands and their ascorbic acid concentration and content were unaffected. No significant histopathological changes were observed in treated goats.

Some pharmacological and toxicological properties of furazolidone

The pharmacological and toxicological properties of furazolidone have been briefly reviewed. Among the most important pharmacological actions of furazolidone is the inhibition of mono- and diamine oxidase activities, which seem to depend, at least in some species, on the presence of the gut flora. The drug also seems to interfere with the utilization of thiamin, which is probably instrumental in the production of anorexia and loss of body weight of the treated animals. Furazolidone is known to induce a condition of cardiomyopathy in turkeys, which could be used as a model to study alpha 1-antitrypsin deficiency in man. The drug is most toxic to ruminants. The toxic signs observed were of nervous nature. Experiments are in progress in this laboratory to try to explain the mechanism(s) by which this toxicity is brought about. It is uncertain whether the use of furazolidone at the recommended therapeutic dose would result in drug residues in tissues of treated animals. This is a matter of public health importance as the drug has been shown to possess a carcinogenic activity. It is important that a simple and reliable method of identification and estimation of furazolidone residues be devised. More work is needed to elucidate the mode of action and biochemical effects caused by the drug in both the host and the infective organisms.