Document Type

Thesis - Open Access

Award Date

2022

Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

Jonathan Jenks

Keywords

bighorn sheep, chronic carrier, Mycoplasma ovipneumoniae, pathogen persistence, pneumonia, wildlife disease

Abstract

Pneumonia is a major factor affecting populations of free-ranging bighorn sheep (Ovis canadensis) across western North America. Pneumonia can occur in large-scale epizootics, during which greater than half of the population typically dies. After these epizootics, surviving ewes continue to conceive and bear lambs. However, lamb recruitment may remain low due to periodic or annual pneumonia outbreaks causing high lamb mortality rates, sometimes greater than 90%. Our study focused on the Rapid City, South Dakota bighorn sheep (BHS) herd that has recorded pneumonia-induced population decline since 2009. The first objective was to improve lamb health and survival by identifying and removing individuals that chronically carry the pathogen (Mycoplasma ovipneumoniae [Movi]). A previous study that treated the Custer State Park, South Dakota BHS herd during 2016–2017 with the same techniques successfully eliminated chronic Movi carriers and increased lamb recruitment. We treated the Rapid City BHS herd from January 2018 to November 2020. We tested individual BHS for Movi upper respiratory infections using real-time polymerase chain reaction (RT-PCR) and exposure to Movi by a competitive enzyme-linked immunosorbent assay (ELISA). If individual sheep tested positive via RT-PCR for the presence of Movi twice consecutively it was considered a chronic carrier and was removed from the herd. We identified an intermittent carrier as testing positive and negative on different occasions and non-carriers as testing negative for every test. We identified patterns of Movi carriage using Movi testing data from 2016–2020 and deemed individuals as chronic, intermittent, or non-carriers. Over the course of the study, we removed four chronic and five intermittent carriers, and our results suggested that removing intermittent carriers may be necessary to reduce or eliminate Movi persistence in a BHS herd. We monitored the survival of lambs prior to and during carrier removal and our analysis indicated that carrier removal increased lamb survival up to six months in both sub-herds in the Rapid City BHS herd (Spring Creek survival prior to removal= 35.3% [95% CI 15.5%, 56.6%], Spring Creek Survival during removal= 75.5% [95% CI 51.4%, 91.3%]; Rapid Creek survival prior to removal= 8.54% [95% CI 0.45%, 27.4%], Rapid Creek survival during removal= 50.8% [95% CI 28.3%, 72.6%]). Subsequent field testing revealed that we removed all known chronic carriers from the herd and thereafter we documented no pneumonia-related mortalities supporting previous conclusions that carrier removal can increase lamb survival and health. The second objective was to quantify the body condition, diet quality, and diet composition of the ewes (14) in the Rapid City BHS herd post-pneumonia epizootic to better understand the current herd productivity to use as a baseline for future management. Further, we focused on how a ewe's lactation status (i.e., lactating or not lactating) affected its digestive capabilities and diet selection. We collected data from March–August 2020. We used ultrasonography technology and body palpations to obtain body condition data and assessed diet quality and composition through percent fecal nitrogen and metabarcoding analyses, respectively. No significant relationships were found in the body condition and diet data collected. However, we identified that browse species were the primary forage consumed, making up 86.8% of lactating ewe samples and 58.3% of non-lactating ewe samples. This study represents the first attempt to understand the potential effects of nutritional condition post-pneumonia epizootic and provided an additional case study that illuminates diet composition differences between lactating and non-lactating ungulates.

Library of Congress Subject Headings

Bighorn sheep -- Respiratory organs -- Diseases.
Bighorn sheep -- Monitoring -- South Dakota -- Rapid City.
Pneumonia.
Mycoplasma diseases in animals.
Wildlife monitoring -- South Dakota -- Rapid City.

Number of Pages

111

Publisher

South Dakota State University

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Rights Statement

In Copyright