Development of the muskox lungworm, Umingmakstrongylus pallikuukensis (Protostrongylidae), in gastropods in the Arctic

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Abstract
Development of the muskox protostrongylid lungworm, Umingmakstrongylus pallikuukensis, in its slug intermediate host, Deroceras laeve, was investigated under field conditions in the Arctic. Every 2 weeks, from 19 June to 28 August 1997, groups of 10 experimentally infected slugs were placed in tundra enclosures in a mesic sedge meadow near Kugluktuk, Nunavut, Canada. First-stage larvae (L1) infecting slugs on or before 17 July developed to third-stage larvae (L3) in 4–6 weeks. Intensity of L3 in slugs peaked at 6–8 weeks post infection (PI) and then progressively declined by 10, 12, and 48–50 weeks PI. Abundance of L3 in slugs was greatest during mid to late August. L1 infecting slugs on 31 July or later did not develop to L3 before the end of September but overwintered in slugs on the tundra as L1 or as second-stage larvae, completing development to L3 the following summer. The years 1997 and 1998 were exceptionally warm and, in cooler years, rates of larval development may be slower and patterns of availability may differ. The amount of heating (degree-days) accumulated during each trial was calculated using the 8.5°C threshold determined in the laboratory, a 21°C maximum, and either surface, soil, or air temperature. Only degree-days accumulated at the surface were sufficient to correspond to the observed rates of larval development. This enclosure-based system and associated degree-day calculations may be used for predicting the effects of climate and climate change on patterns of parasite development and transmission in the Arctic.