The transmission ecology of Echinococcus multilocularis in a North American urban landscape
Date
2015-01-28
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Abstract
The cestode Echinococcus multilocularis is a trophically-transmitted parasite that is typically maintained in a sylvatic cycle involving wild canid definitive hosts and small mammal intermediate hosts. As etiological agent of Alveolar Echinococcosis in humans, the cestode is currently the third most impacting food-borne parasite globally. Understanding E. multilocularis transmission ecology, combined with reliable diagnostic and surveillance of parasite infection in wild hosts, is crucial for disease prevention and risk management.
In Calgary, Canada, E. multilocularis was found to infect 29.5% (n = 61) of road-killed urban coyotes (Canis latrans) collected in 2009-2010. For the detection of E. multilocularis eggs in coyote feces, sugar fecal flotation showed lower sensitivity than the ZnCl2 centrifugation and sedimentation protocol (0.46 vs. 0.75). The latter technique is therefore recommended for screening of canid hosts.
This study provided the first evidence of an urban sylvatic cycle of E. multilocularis in North America. Parasite prevalence in coyote feces was shown to vary temporally (10.5-43.5%) and spatially (5.3-61.5%) across five city parks, and infection of small mammal intermediate hosts was documented in three competent species (prevalence ranging between 0.7 and 1.4%). Genotyping coyote feces (n = 142) at 4-6 microsatellite loci allowed to correct for repeated sampling of individuals, and to estimate an overall parasite prevalence of 25.0%. Importantly, individual patterns of infection (i.e., parasite egg intensity in feces) allowed to observe temporal variations in parasite transmission that were not detected when examining fecal samples of unknown identity. By looking at the recovery of parasite eggs in genotyped feces over time, a re-infection rate of 57% (n =7) was estimated for coyotes in an area of parasite hyper-endemicity.
Winter was a crucial period for E. multilocularis transmission, as the encounter rate of coyote with the parasite (number of infected hosts ingested) was higher than any other season (95% CI: 1.0-22.4). Voles (Microtus pennsylvanicus and Myodes gapperi) were consumed by coyotes proportionally more than their availability, and likely played a key role for the maintenance of the urban sylvatic life-cycle of E. multilocularis in this urban landscape.
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Keywords
Ecology, Parasitology, Public Health
Citation
Liccioli, S. (2015). The transmission ecology of Echinococcus multilocularis in a North American urban landscape (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/28404