Abstract
The pathogenicity of Babesia ovata was studies clinically, hematologically and blood-chemically in splenectomized and non-splenectomized cattle experimentally infected with this parasite. In six splenectomized cattle, the parasite multiplied markedly in the blood stream soon after inoculation. An elevated rectal temperature, anorexia, severe anemia, icterus and hemoglobinuria were observed clinically. Two of six cattle died. Hematologically, a marked decrease was observed in erythrocyte count, packed cell volume, hemoglobin level, leukocyte count and platelet count, as parasitemia increased in severity. Conjugated and unconjugated bilirubin, glutamic oxalacetic transaminase, blood urea nitrogen and uric acid levels were elevated, but total serum protein and blood glucose levels declined during the hemolytic phase. On urinalysis, hemoglobinuria, urobilinuria and proteinuria were present at the same time. It is considered that these changes have close relation to the multiplication of parasites in the blood stream and that the higher the intensity of parasitemia, the severer clinical symptoms are. Parasitemia was very mild in six non-splenectomized cattle in which anemia was also mild. Consequently, clinical, hematological and blood-chemical changes were relatively mild in these cattle. Therefore, it is considered that the pathogenicity of Babesia ovata was characterized not only by anemia, icterus and hemoglobinuria, but also by hepatic and renal dysfunction when parasites multiplied markedly in the blood stream due to such immuno-suppressive factors as splenectomy.
