Bovine Coccidiosis: Dynamics of infection in grazing cattle and the potential role of stress and immunity

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dc.contributor.authorLucas, Aaron Scotten
dc.contributor.committeechairZajac, Anne M.en
dc.contributor.committeememberLindsay, David S.en
dc.contributor.committeememberWitonsky, Sharon G.en
dc.contributor.committeememberElvinger, Francois C.en
dc.contributor.committeememberNeel, James P. S.en
dc.contributor.committeememberSwecker, William S. Jr.en
dc.contributor.departmentVeterinary Medical Sciencesen
dc.date.accessioned2014-03-14T21:17:39Zen
dc.date.adate2011-09-08en
dc.date.available2014-03-14T21:17:39Zen
dc.date.issued2011-08-02en
dc.date.rdate2011-09-08en
dc.date.sdate2011-08-11en
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
dc.description.degreePh. D.en
dc.identifier.otheretd-08112011-100406en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-08112011-100406/en
dc.identifier.urihttp://hdl.handle.net/10919/39126en
dc.publisherVirginia Techen
dc.relation.haspartLucas_AS_D_2011.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectEimeriaen
dc.subjectweaningen
dc.subjectcattleen
dc.subjectcalvesen
dc.subjectstressen
dc.subjectIFN-γen
dc.subjectflow cytometryen
dc.subjectT-lymphocytesen
dc.subjectcytokinesen
dc.titleBovine Coccidiosis: Dynamics of infection in grazing cattle and the potential role of stress and immunityen
dc.typeDissertationen
thesis.degree.disciplineVeterinary Medical Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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