Effect of snow cover on the off-host survival of Dermacentor variabilis (Acari: Ixodidae) larvae
Date
2024-01
Authors
Diyes, Chulantha P
Yunik, Matthew E M
Dergousoff, Shaun J
Chilton, Neil
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Journal of Medical Entomology
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Article
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Abstract
The geographical range of the American dog tick, Dermacentor variabilis (Say), in Canada continues to expand northwards into areas with colder winter temperatures. Understanding what influences the off-host survival of D. variabilis over winter is important for predicting the northern distributional limit of this species. A field experiment was conducted to determine the effect of snow cover on the off-host survival of unfed D. variabilis larvae from a population situated near the northern distributional limit in Saskatchewan, Canada. Ticks were placed in tubes within 1 of 9 field enclosures (tickaria) in early fall. The 9 tickaria were divided into 3 equal treatment groups: no snow cover, natural snow cover (maximum depth of 25 cm) and extra snow cover (maximum depth of 32 cm). Tick survival was measured in mid-winter and in early spring (i.e., ~17 and ~26 wk after start of experiment). The results showed that snow cover had a significant impact on the relative humidity, but not temperature, in the tickaria. Larvae in tickaria with no snow cover had a higher mortality rate (27%) than larvae in tickaria with natural snow cover (6%) or extra snow cover (4%). Although snow cover enhanced off-host survival, many individuals were able to survive in sub-zero temperatures under leaf litter in the absence of continuous snow cover for a period of 108 days. These findings have implications for the construction of predictive models to determine the northern distributional limits of D. variabilis, a species that is an important vector of several pathogens.
Description
This article has been accepted for publication in the Journal of Medical Entomology Published by Oxford University Press. Chulantha P Diyes, Matthew E M Yunik, Shaun J Dergousoff, Neil B Chilton, Effect of snow cover on the off-host survival of Dermacentor variabilis (Acari: Ixodidae) larvae, Journal of Medical Entomology, Volume 61, Issue 1, January 2024, Pages 46–54, https://doi.org/10.1093/jme/tjad150
Keywords
American dog tick, unfed larvae, survival, snow cover, overwintering
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DOI
https://doi.org/10.1093/jme/tjad150