Determining the Geographic Distribution of Filarioid Nematodes in Caribou in Canada
Date
2023-11-16
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Abstract
The caribou (Rangifer tarandus sspp.) is a keystone wildlife species in northern ecosystems that plays a central role in the lives of the Indigenous People as a cultural and spiritual icon. The Arctic is currently experiencing unpredictable changes due to various factors, including climate change, and warming temperatures and change in precipitation in the Arctic facilitate the transmission of arthropod-borne parasites. Caribou are hosts to several vector-borne parasites, which includes protozoans such as Babesia odocoilei and Besnoitia tarandi, and filarioid nematodes of the genus Setaria, Onchocerca, and Rumenfilaria. Some caribou populations are declining as a result of rapidly changing climate and multiple stressors, including these vector-borne parasites. Filarioids are an important cause of morbidity, and occasional mortality in Rangifer in Fennoscandia. However, the ecology and epidemiology of these parasites in caribou in North America, including Canada is unknown. The objective of this study was to determine the parasitic diversity and geographic distribution of filarioid nematodes in three Canadian designatable units (DU) of caribou, representing Barrenground, Boreal Woodland and Dolphin & Union Caribou from Northwest Territories, Nunavut, and Newfoundland & Labrador. Genomic DNA extracted from 768 blood samples was screened using real-time PCR. The positive samples were Sanger sequenced to identify the parasite present. Based on the sequencing results, we identified Setaria yehi and Onchocerca cervipedis s.l. I then standardized a TaqMan probe based duplex droplet digital PCR (ddPCR) protocol for the simultaneous detection of S. yehi and O. cervipedis s.l. I adopted a conservative approach for ddPCR to make the technique time- and cost-effective. Out of 768 samples, 136 samples were screened using ddPCR. Based on real-time PCR results, 8/768 samples were positive. Setaria yehi and O. cervipedis s.l. were present in 4 separate samples (0.5%) each. Using ddPCR, 60/136 samples were positive (44.1%). Setaria yehi was the most common one with 40/136 positive samples (29.4%); Onchocerca cervipedis s.l. was present in 10/136 samples (7.3%), and 10/136 samples (7.3%) had a co-infection. Setaria yehi was detected from all three DUs tested. Onchocerca cervipedis s.l. were found from Barrenground and Boreal Woodland caribou, but not from the Dolphin and Union caribou herd. Through this broad-based survey and by developing and implementing advanced molecular methodologies, I have detailed the distribution and diversity of S. yehi and O. cervipedis s.l. in parts of three Canadian DUs of caribou. Filarioids are important pathogen nematodes which can cause chronic illness in Rangifer and understanding their distribution and epidemiology helps to know the impacts of these parasites in Canadian caribou populations. The knowledge I obtained from my study will set the stage and provide methods for the further elucidation of the epidemiology of these parasites in Canada across the range of caribou.
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Keywords
Filarioid, Nematode, Rangifer tarandus, Setaria yehi, Onchocerca cervipedis, ddPCR, Canadian Arctic, Caribou, Vectorborne parasites, Climate change
Citation
Mariyam Thomas, A. (2023). Determining the geographic distribution of filarioid nematodes in caribou in Canada (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.