| Abstract: | Experiments were performed to separate Babesia bigemina from Babesia argentine, Babesia major, and Anaplasma marginale. The method of separation was rapid passage through 5 splenectomized calves. Five blood passages were carried out in 6 1/2 days. Babesia argentine, B. major, and A. marginale were eliminated as contaminants after 4 passages. A frozen stabilate of the isolated B. bigemina was established. A method for the preparation and examination of combination thin and thick blood films for the detection of Babesia parasitemia was developed. The technique for the staining of the combination thin and thick films involved the use of a phosphate buffered Giemsa stain solution containing alkyl phenoxy polyethoxy ethanol. Babesial complement fixation (CF) antigens were also prepared and titrated for use in a CF microtiter procedure. Babesia bigemina parasitized blood exposed to varied doses gamma radiation up to 60 kRad was inoculated into calves. Calves infected with 1 x 10^10 B. bigemina parasitized erythrocytes exposed to doses up to and including 30 kRad developed progressive parasitemias. Some calves receiving 1 x 10^10 parasitized erythrocytes irradiated at levels of 36 and 42 kRad did not develop progressive infections. Progressive infections were prevented by exposure to irradiation at 48 kRad or higher. Subinoculations into susceptible splenectomized calves from parasites thus treated failed to produce active infections. ... |
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