Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

Jonathan A. Jenks


Bighorn Sheep, Black Hills, Mycoplasma ovipneumoniae, pneumonia, wildlife


Infected individuals vary in their contribution to disease persistence, and chronically infected individuals may sustain disease in a population. One disease that might persist in a population through chronically infected individuals is pneumonia in wild sheep. Mycoplasma ovipneumoniae (Mo), a pathogen of Caprinae commonly present in domestic sheep and goats, strongly correlates with pneumonia epizootics when it infects wild sheep populations. These epizootics can cause 40-100% herd mortality in an initial all-age dieoff, precipitate annual lamb mortality as high as 100% in following years, and sustain adult mortality long after initial all-age dieoffs. We conducted an experiment in the Black Hills of South Dakota to evaluate whether we could eliminate Mo infection and pneumonia in a bighorn sheep population by removing chronically infected individuals, termed “chronic shedders”. We classified chronic shedders as adults that consistently tested positive for Mo on multiple nasal swabs collected over a 20 month period. We identified and removed chronic shedders from a treatment population (Custer State Park) and left the adjacent control population (Rapid City) unmanipulated. Mo and respiratory disease were not detected following treatment, whereas Mo persisted in the control herd and pneumonia was the leading source of mortality among both adults and lambs. Adult and juvenile annual survival in the treatment population averaged 93% and 76%, respectively, as compared to 83% and 35% in the control herd. Overall mortality hazard for adults was significantly reduced in the treatment population relative to the control (β_treatment=-0.95, CI=-2.03, -0.039), as was the hazard for lambs (β_treatment=-1.40, CI=-2.42, -0.46). These results support the hypothesis that Mo is the primary causative agent of epizootics of pneumonia in bighorn sheep, are a proof-of-concept of epidemics being sustained by chronic carriage, and provide direction for management actions aimed at treating respiratory disease in bighorn sheep.

Library of Congress Subject Headings

Bighorn sheep -- Diseases.
Bighorn sheep -- Black Hills (S.D. and Wyo.)
Mycoplasma diseases in animals.


Includes bibliographical references



Number of Pages



South Dakota State University



Rights Statement

In Copyright