Management of Psoroptes in Free Ranging Bighorn Sheep

Abstract

The overall objective of this thesis is to address gaps in knowledge and provide tools that will aid in the management of the psoroptic mange outbreak in bighorn sheep (Ovis canadensis) of the Okanagan region of Canada. A multi-pronged approach was taken including outbreak investigation, development of disease detection tools, investigation of treatment options, and finally review of management action approaches. Based on comparison of Psoroptes morphology and mitochondrial gene sequencing, the most likely source of the outbreak was determined to be a cross-species transmission event from rabbits. This transmission likely occurred on the Okanagan Game Farm, closed in 1999, and therefore new exogenous sources of disease in the area are unlikely. A commercially available enzyme linked immunosorbent assay (ELISA) marketed for Psoroptes detection in domestic sheep was optimized for use with bighorn sheep serum with a test sensitivity of 98.7% and specificity of 94.0%. A treatment trial conducted on Psoroptes-infested Canadian bighorn sheep found that both the injection of extended-release eprinomectin and topical application of fluralaner were unsuccessful in eliminating mite infestations; meanwhile, orally administered fluralaner cleared the infestations and greatly improved clinical signs following a single treatment when used at either 5mg/kg or 25mg/kg dosages. The fence and handling systems used in the treatment trial for housing and control of bighorn sheep movement were reviewed and critical weaknesses in design and construction were identified to address a gap in literature on bighorn sheep fencing requirements. The complexity of population-level application of new knowledge often involves ongoing uncertainty leading to delays in management action. While Psoroptes has rarely been managed in wild sheep, respiratory disease has received considerably more attention. Interviews conducted with 13 wildlife professionals involved in the management of bighorn sheep respiratory disease were used to help identify common challenges and opportunities in the management of North American bighorn sheep. Investigation of strategies aimed at preventing pathogen introduction into naïve herds is essential before eradication efforts can be considered. A more systematic approach to addressing sources of disease introduction is a necessary step in the development of management options for both respiratory disease and Psoroptes. Four main types of barriers that impede management action were identified; social and political challenges, resource limitations, knowledge barriers, and physical/landscape barriers. Some of these are beyond the control of wildlife managers while strategies to address others are discussed. Increased attention to the human dimensions of wildlife management and the application of an adaptive management approach is needed. The tools developed throughout this thesis and the lessons learned through these interviews are valuable resources for wildlife managers to use when engaging stakeholders in developing an adaptive management plan for Psoroptes in British Columbia.