Dissertation
Immune Responses of Domestic Sheep (Ovis aries) and Bighorn Sheep (Ovis Canadensis) to Mycoplasma ovipneumoniae
Doctor of Philosophy (PhD), Washington State University
01/2019
Handle:
https://hdl.handle.net/2376/111086
Abstract
Pneumonia is a disease that limits population recovery of bighorn sheep (Ovis canadensis, BHS). An emerging body of evidence supports Mycoplasma ovipneumoniae as the initiating pathogen in polymicrobial BHS epizootic pneumonia. Pneumonia in BHS occurs in epizootics with generally high morbidity and variable mortality (5-95%) in all age classes. In subsequent years, recurrent pneumonia epizootics often result in poor lamb recruitment. In well-studied BHS herds in the western U.S., this lamb pneumonia pattern is observed for several years and sometimes decades, though it may be interspersed with seasons of normal lamb recruitment. This persistent poor lamb recruitment limits BHS population growth, despite management efforts. Domestic sheep (Ovis aries, DS) are suspected reservoirs of BHS pneumonia; commingling studies demonstrated pneumonia and high death rates for BHS while DS remained healthy. Several sheep respiratory pathogens have been identified and recognized as important contributors to BHS pneumonia, but M. ovipneumoniae is the only pathogen in which single genetic strain types link affected sheep within pneumonia outbreaks. M. ovipneumoniae is an opportunistic pathogen that damages respiratory cilia and compromises mucociliary clearance, permitting invasion of secondary pathogens, resulting in polymicrobial pneumonia. Several observations suggest BHS are more susceptible to M. ovipneumoniae-related pneumonia than DS. Prevalence in the U.S. is high in DS herds (88.5%) while lamb mortality due to pneumonia is comparatively low, <1.5% annually. In DS, M. ovipneumoniae causes disease referred to as coughing syndrome, chronic, non-progressive pneumonia, or atypical pneumonia, and generally results in low lamb mortality. In contrast, the persistent high lamb mortality in BHS herds often limit population growth. Evidence exists for different age of infection for each species. Small samples demonstrated domestic lambs were not infected with M. ovipneumoniae until six weeks of age or later, while bighorn lambs were infected by ten days of age and at highest risk of death from pneumonia between 28-56 days old. Here, potential immune response differences between BHS and DS are investigated which may explain differences in morbidity and mortality of M. ovipneumoniae-related pneumonia in BHS, especially lambs. These findings may be applied to BHS herd management efforts to help pneumonic populations recover.
Metrics
56 File views/ downloads
27 Record Views
Details
- Title
- Immune Responses of Domestic Sheep (Ovis aries) and Bighorn Sheep (Ovis Canadensis) to Mycoplasma ovipneumoniae
- Creators
- Melissa Ackerman
- Contributors
- Thomas E Besser (Advisor)Donald P Knowles (Advisor)David A Schneider (Committee Member)Charles Frevert (Committee Member)George M Barrington (Committee Member)Steven M Parish (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Veterinary Medicine, College of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 68
- Identifiers
- 99900581416801842
- Language
- English
- Resource Type
- Dissertation