Browsing by Author "Kafle, Pratap"
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- ItemOpen AccessClimate Change and Range Expansion of Protostrongylid Nematodes in the Canadian Arctic(2018-09-19) Kafle, Pratap; Kutz, Susan; Checkley, Sylvia L.; Massolo, Alessandro; Lejeune, ManigandanThrough this doctoral research, I aimed to determine the diversity, distribution and abundances of protostrongylids in muskoxen and caribou from several sites in Subarctic and Arctic Canada and investigate the northward range expansion of Umingmakstrongylus pallikuukensis and Varestrongylus eleguneniensis in relation to Arctic warming. I first developed morphological keys to differentiate the first stage larvae (L1) of U. pallikuukensis, V. eleguneniensis and Parelaphostrongylus andersoni. This enabled me to identify L1 to the species level and determine the intensity of infections. Secondly, I analyzed over 1600 muskox and caribou fecal samples, and 40 muskox lung samples to determine the diversity, distribution and abundance patterns of protostrongylids. I found that the diversity and abundance of protostrongylids varied geographically. Both U. pallikuukensis and V. eleguneniensis had expanded their ranges and increased in abundance on Victoria Island between 2013 and 2017, with U. pallikuukensis expanding its range faster than V. eleguneniensis. I also detected P. andersoni in the Dolphin and Union caribou herd. In the third part of the study, I determined the important life cycle parameters for U. pallikuukensis and V. eleguneniensis through lab experiments. I demonstrated that V. eleguneniensis has higher thermal requirements for larval development inside the intermediate host, a shorter prepatent and patent period, and lower fecundity than U. pallikuukensis. Based on these findings I hypothesized that higher thermal requirements and lower fecundity might be limiting the rate and extent of range expansion for V. eleguneniensis. Finally, to map the thermal niches of U. pallikuukensis and V. eleguneniensis from 1980 through to 2017, I parametrized a process-based mechanistic model (Degree-day model) using data derived from the lab experiments, the literature, and high-resolution temperature data from a regional climate model. Models indicated a substantial expansion in the zones of climatic suitability for both parasites during the study period with the realized niches of both parasites lagging behind the expansion of their thermal niches. This work contributes to the field of Arctic parasitology by providing simple and effective diagnostic tools for protostrongylids, and adding to the present knowledge on diversity, distribution, abundance as well as ecology of protostrongylid nematodes. Finally, by using a multifaceted approach to investigate the patterns of parasite emergence in the Arctic, this study contributes to the overall understanding of disease emergence in a rapidly changing ecosystem.
- ItemOpen AccessCorrection to: Temperature-dependent development and freezing survival of protostrongylid nematodes of Arctic ungulates: implications for transmission(2018-08-02) Kafle, Pratap; Peacock, Stephanie J; Grond, Sarah; Orsel, Karin; Kutz, SusanUnfortunately, the original version of this article [1] contained an error.
- ItemOpen AccessTemperature-dependent development and freezing survival of protostrongylid nematodes of Arctic ungulates: implications for transmission(2018-07-09) Kafle, Pratap; Peacock, Stephanie J; Grond, Sarah; Orsel, Karin; Kutz, SusanAbstract Background Umingmakstrongylus pallikuukensis and Varestrongylus eleguneniensis are two potentially pathogenic lungworms of caribou and muskoxen in the Canadian Arctic. These parasites are currently undergoing northward range expansion at differential rates. It is hypothesized that their invasion and spread to the Canadian Arctic Archipelago are in part driven by climate warming. However, very little is known regarding their physiological ecology, limiting our ability to parameterize ecological models to test these hypotheses and make meaningful predictions. In this study, the developmental parameters of V. eleguneniensis inside a gastropod intermediate host were determined and freezing survival of U. pallikuukensis and V. eleguneniensis were compared. Methods Slug intermediate hosts, Deroceras laeve, were collected from their natural habitat and experimentally infected with first-stage larvae (L1) of V. eleguneniensis. Development of L1 to third-stage larvae (L3) in D. laeve was studied at constant temperature treatments from 8.5 to 24 °C. To determine freezing survival, freshly collected L1 of both parasite species were held in water at subzero temperatures from -10 to -80 °C, and the number of L1 surviving were counted at 2, 7, 30, 90 and 180 days. Results The lower threshold temperature (T0) below which the larvae of V. eleguneniensis did not develop into L3 was 9.54 °C and the degree-days required for development (DD) was 171.25. Both U. pallikuukensis and V. eleguneniensis showed remarkable freeze tolerance: more than 80% of L1 survived across all temperatures and durations. Larval survival decreased with freezing duration but did not differ between the two species. Conclusion Both U. pallikuukensis and V. eleguneniensis have high freezing survival that allows them to survive severe Arctic winters. The higher T0 and DD of V. eleguneniensis compared to U. pallikuukensis may contribute to the comparatively slower range expansion of the former. Our study advances knowledge of Arctic parasitology and provides ecological and physiological data that can be useful for parameterizing ecological models.