The invasion process of the European strain of Echinococcus multilocularis in Western Canada
Date
2022-02
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Abstract
Genetic studies on Echinococcus multilocularis (Em), the causative agent of human alveolar echinococcosis (AE), are essential to understand the ecological and evolutionary processes underlying changes in the geographic distribution of this parasite, and to assess the potential impact on public health. The recent detection of European-like haplotypes circulating in wild hosts in Western Canada, and the unprecedented detection of human AE cases in Alberta, make it a priority to assess the extent of the distribution of this strain and its origin(s) into Canada. The overall aim of my thesis was to investigate the invasion process of the European strain of Em in Western Canada. I reviewed the invasions by parasites with complex-life cycles using the invasion of the European strain as a model to develop an ecological framework for investigating the invasion of parasites transmitted in predator-prey systems. Then, I developed a real-time PCR assay to detect co-infections of Em and E. canadensis in fecal and worm-mixed samples, providing the first evidence of co-infections of these two parasites in red foxes and coyotes, and the first molecularly confirmed record of E. canadensis (G10) in coyotes. When used along with an automated magnetic bead-based DNA extraction method, the real-time PCR test proved to have a high sensitivity to detect Em in fecal samples, increasing efficiency and throughput. The genetic analysis using deep amplicon sequencing and multiple mitochondrial and nuclear markers showed a lower intraspecific diversity and a higher abundance of the European-type haplotypes. Moreover, most genetic variants were closely related to the original European clade, with the dominance of one variant in each province and low genetic diversity of Em, supporting the hypothesis of a relatively recent introduction. The spatial analysis showed a genetic discontinuity between western provinces, suggesting different founder events and isolation by distance of some genetic variants. Finally, although the prevalence of Em infection was higher in red foxes than coyotes, there was a higher proportion of coyotes with high intensity of infection, even at lower population densities than red foxes. Therefore, coyotes might be considered the main spreaders of the European strain in Alberta.
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emerging infectious diseases, host-parasite interactions, strain introductions, co-infections, host-partitioning
Citation
Santa, M. A. (2022). The invasion process of the European strain of Echinococcus multilocularis in Western Canada (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.