Dissertation
Mannheimia haemolytica infection in bighorn sheep and domestic sheep: Cytokine expression and transfer of passive immunity
Washington State University
Doctor of Philosophy (PhD), Washington State University
08/2010
DOI:
https://doi.org/10.7273/000006029
Abstract
Respiratory disease caused by bacteria including Mannheimia haemolytica has contributed significantly to the drastic decline of bighorn sheep (BHS, Ovis canadensis) population of North America, from an estimated two million animals at the beginning of the nineteenth century to less than 70,000 today. Although M. haemolytica causes pneumonia in a number of ruminant species, BHS are particularly susceptible. Bighorn sheep exhibit much greater susceptibility, and enhanced pathology in response, to infection with M. haemolytica, in comparison to the closely related domestic sheep (DS, Ovis aries). The molecular and cellular basis for this difference is not clear. The studies presented here focused on the differences in the immune response of BHS and DS to M. haemolytica, particularly the expression of proinflammatory cytokines. In vitro experiments revealed that the polymorphonuclear leukocytes (PMNs) of BHS produced remarkably higher levels of the potent chemoattractant interleukin-8 than did those of DS. In vivo experiments revealed that bronchoalveolar lavage fluid and lesional lung tissue of BHS infected with M. haemolytica contained much higher levels of interleukin-8 than those of infected DS, confirming the in vitro finding. Higher levels of interleukin-8, and possibly other pro-inflammatory cytokines, in the inflamed lung tissue of infected BHS are likely responsible for the overwhelming influx of PMNs, and the subsequent lung tissue damage caused by leukotoxin-induced lysis and degranulation of these cells. In order to understand the basis for the impaired lamb recruitment following pneumonia outbreaks in BHS herds, these studies also compared the transfer of passive immunity to M. haemolytica from BHS and DS ewes to their lambs. Transfer of antibodies against whole M. haemolytica, and leukotoxin-neutralizing antibodies were analyzed. In comparison to DS lambs, BHS lambs had significantly lower titers of these antibodies which are known to be protective against M. haemolytica infection. The lower titers of these antibodies in BHS lambs was due to significantly lower titers of these antibodies in BHS ewes, in comparison to DS ewes. These studies have discovered key differences in the immune response of BHS and DS which likely contribute to the particular susceptibility of BHS to M. haemolytica-caused pneumonia.
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Details
- Title
- Mannheimia haemolytica infection in bighorn sheep and domestic sheep
- Creators
- Caroline Nanette Herndon
- Contributors
- Subramaniam Srikumaran (Chair)Thomas Eugene Besser (Committee Member) - Washington State University, Department of Veterinary Microbiology and PathologyWendy C Brown (Committee Member)William J. Foreyt (Committee Member)KEVIN KARL LAHMERS (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- College of Veterinary Medicine
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 98
- Identifiers
- 99901055126701842
- Language
- English
- Resource Type
- Dissertation