Immune response of cattle inoculated with irradiated Babesia bigemina : a dissertation /
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| Other Authors: | , , , |
| Format: | Thesis Book |
| Language: | English |
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[College Station, Tex.] :
[Texas A&M University],
[1971]
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| Subjects: |
| Abstract: | 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 10¹⁰ B. bigemina parasitized erythrocytes exposed to doses up to and including 30 kRad developed progressive parasitemias. Some calves receiving 1 x 10¹⁰ 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. In addition to a lower infection rate brought about by irradiated parasites, calves that did become infected had prolonged prepatent periods and lower maximum parasitemias. Control calves, however, that had been inoculated with 1 x 10⁷ nonirrated parasitized enrythrocytes also had prolonged prepatent periods and lower maximum parasitemias. Therefore, the prolonged prepatent periods and lower maximum parasitemias in calves that had recieved 1 x 10¹⁰ irradiated B. bigemina could have been partly due to a reduction in the number of viable parasites injected. The finding that calves inoculated with 1 x 10⁷ nonirradiated parasitized erythrocytes had prolonged prepatent periods and lower maxium parasitemias indicate that such a standardized inoculum might be of use as a vaccine to produce an attenuated infection. A degree of acquired resistance to infection with B. bigemina developed in calves after 1 inoculation with B. bigemina parasitized to suppress muliplication of the Babesia and to permit calves to survive otherwise severe clinical infections with nonirradiated parasites. There was also less erythrocytic destruction and a smaller increase in recutal temperatures following challenge. Presumably, the irradiated parasites were responsible for the development of resistance since irradiated nonparasitized blood did not produce a discernable acquired resistance. The observation that inoculation of calves with irradiated B. bigemina stimulated a degree of protective immunity, suggests that the presence of replicating Babesia in the host is not necessary for the development of acquired resistance. The acquired resistance to infection with B. bigemina developed in calves inoculated with 1 x 10¹⁰ B. bigemina irradiated at 48 and 60 kRad was similar to the acquired resistance developed in calves inoculated with 1 x 10¹⁰ nonirradiated B. bigemina. It seems likely that the protective immunity produced with irradiated B. bigemina may be similar to that produced with living pathogenic B. bigemina in non-fatal infections. The acquired resistance to infection with B. bigemina developed in calves inoculated with 1 x 10¹⁰ B. bigemina irradiated at 48 and 60 kRad was much greater than the acquired resistance to infection developed in calves inoculated with 1 x 10¹⁰ heat killed B. bigemina. Thus, it seems likely that immunization with irradiated Babesia may provide the special immunological properties of living parasites important for producing a strong immunity while suppressing the pathogenic effects of the parasite. The Babesia parasites could be irradiated and frozen without apparent loss of immunizing properties. |
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| Item Description: | Vita. "Major Subject: Veterinary Microbiology". "Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of Doctor of Philosophy December 1971". |
| Physical Description: | xv, 136 leaves : illustrations ; 29 cm |