| Summary: | Populations of bighorn sheep have been severely depleted by respiratory disease during the past one hundred years. Although numerous pathogens contribute to the complex etiology of this disease, physiological and environmental factors may also contribute to the frequency and severity of this disease. Therefore, the primary objectives of this study were to (a) assess immune competence and physiological and parasitological status of healthy and diseased bighorn sheep and (b) determine which physiological and environmental factors contribute to immune competence. Since lymphocyte transformation appears to be a sensitive index of immune competence, in a second part of this study attempts were made to miniaturize an existing macroleukocyte culture technique. If simple enough, such a technique could be used to evaluate the immune competence of free ranging animals. Results of this study indicate that immune competence is variable between individuals and may oscillate preceeding episodes of disease. However, low immune reactivity, depressed nutritional status and increased levels of general inflammation appear to occur during episodes of disease. Although numerous variables contribute to immune competence, high levels of seromucoid were associated with low immune reactivity. In a second part of this study suggestions were made for the development of a microlymphocyte culture. Although the data collected in this preliminary study suggest that this technique may be possible to assess immune reactivity in the field, further investigations are necessary to standardize this method. === Land and Food Systems, Faculty of === Graduate
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