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dc.contributor.authorLucas, Aaron Scotten_US
dc.date.accessioned2014-03-14T21:17:39Z
dc.date.available2014-03-14T21:17:39Z
dc.date.issued2011-08-02en_US
dc.identifier.otheretd-08112011-100406en_US
dc.identifier.urihttp://hdl.handle.net/10919/39126
dc.description.abstractEimerian parasites infect cattle worldwide. Information on the infection dynamics of these parasites is lacking in the central Appalachian region of the United States. Studies aimed at characterizing the seasonal dynamics of eimerian parasites in this region were carried out in order to assess the impact of these organisms in grazing systems. In these studies the prevalence of Eimeria spp. infection was highest in calves less than one year of age and subsequently decreased to stable levels in older animals. Although E. bovis was the most common species identified in calves, heifers and cows, mixed species infections dominated. Additional studies were carried out to investigate the effect of stress on Eimeria spp. infection in beef calves. Lower stress, two-stage, weaning methods had no effect on Eimeria spp. infection dynamics in beef calves. These findings must be interpreted in light of the fact that calves used in this study were not managed in a way typical of many calves in the U.S.A. The fact that they were only transported short distances, never commingled, or exposed to a livestock market may explain why a rise in post weaning FOC was not observed. A model of stress- induced coccidiosis was developed using dexamethasone and E. bovis challenge. In this model, an oral challenge of at least 500,000 sporulated E. bovis oocysts in addition to dexamethasone injection at 7 days post challenge increased subsequent FOC. Further investigation of the immune response to E. bovis challenge during times of stress indicates that stress-induced suppression of cell mediated immunity and E. bovis challenge are required to increase subsequent oocyst shedding. These findings may represent the mechanism associated with stress-induced outbreaks of coccidiosis reported to occur in beef cattle in the United States.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartLucas_AS_D_2011.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectEimeriaen_US
dc.subjectweaningen_US
dc.subjectcattleen_US
dc.subjectcalvesen_US
dc.subjectstressen_US
dc.subjectIFN-γen_US
dc.subjectflow cytometryen_US
dc.subjectT-lymphocytesen_US
dc.subjectcytokinesen_US
dc.titleBovine Coccidiosis: Dynamics of infection in grazing cattle and the potential role of stress and immunityen_US
dc.typeDissertationen_US
dc.contributor.departmentVeterinary Medical Sciencesen_US
dc.description.degreePh. D.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineVeterinary Medical Sciencesen_US
dc.contributor.committeechairZajac, Anne M.en_US
dc.contributor.committeememberLindsay, David S.en_US
dc.contributor.committeememberWitonsky, Sharon G.en_US
dc.contributor.committeememberElvinger, Francois C.en_US
dc.contributor.committeememberNeel, James P. S.en_US
dc.contributor.committeememberSwecker, William S. Jr.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-08112011-100406/en_US
dc.date.sdate2011-08-11en_US
dc.date.rdate2011-09-08
dc.date.adate2011-09-08en_US


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