Echinococcus multilocularis is a zoonotic, trophically-transmitted cestode typically maintained within a sylvatic cycle involving wild canid definitive hosts and small mammal intermediate hosts. Herein we provide a synthesis of multiannual research conducted in Calgary, Alberta, in which the coyote (Canis latrans) is the main wild definitive host. The study was conducted in five different city parks, collecting coyote feces along fixed routes and sampling small mammals to detect infections in intermediate hosts. Coyote feces were analyzed with a ZnCl2 centrifugation and sedimentation protocol to isolate Taeniidae eggs, which were subsequently identified through species-specific PCR. Feces were also used to quantify consumption of small mammal preys and to identify individual coyotes through non-invasive genotyping conducted at 4-6 microsatellite loci. Coyote genotypes and fecal parasitology were combined to assess true parasite prevalence and individual infection patterns.
This study provided the first evidence of an urban sylvatic cycle of E. multilocularis in North America, and showed an overall prevalence in coyote feces of 25% with significant temporal and spatial variation across seasons (10.5-43.5%) and city parks (5.3-61.5%). These variations were in accordance with availability and consumption of three intermediate host species and their levels of parasite infection (0.7-1.4%). Genotyping coyote feces allowed correcting for repeated fecal sampling of the same individuals. More importantly, it allowed us to follow individual patterns of infection and observe temporal variations in parasite transmission that could not be detected when examining feces of unknown identity. Winter was a crucial period for E. multilocularis transmission, as the encounter rate of coyotes with the parasite was estimated to be higher than any other season (95% CI: 1.0-22.4 infected hosts ingested). Voles (Microtus pennsylvanicus and Myodes gapperi) were preyed upon proportionally more than their availability, and likely played a key role for the maintenance of the sylvatic life-cycle of E. multilocularis in this urban landscape.