Do bank voles (Myodes glareolus) trapped in live and lethal traps show differences in tick burden?

Abstract

In studies assessing tick abundance, the use of live traps to capture and euthanize rodent hosts is a commonly used method to determine their burden. However, captive animals can experience debilitating or fatal capture stress as a result prior to collection. An alternative method is the use of lethal traps, but this can potentially lead to tick drop-off between the time of capture and collection. In this study, in order to determine whether subjecting animals to capture stress is inevitable, we tested the difference in sheep tick (Ixodes ricinus) larval burdens between bank voles (Myodes glareolus) captured alive and euthanized, and lethally trapped bank voles. During 2017 and 2018, 1318 bank voles were captured using live (Ugglan Special no. 2) and lethal (Rapp2 Mousetrap) traps during two consecutive years over three seasons in two locations in Norway. Voles captured alive would remain captive until euthanized, while lethally trapped voles were killed instantly upon capture. Loglinear models, accounting for overdispersion, were used to determine whether trap type was influencing observed tick burden. Bank voles captured in lethal traps carried 5.7% more larvae compared to euthanized voles captured in live traps, but this difference was not significant (p = 0.420). Males were overall captured 2.7 times more frequently than females, and the sex ratio was equal in both trap types. This study shows that the use of lethal traps to determine tick burden of rodents is sufficiently reliable, without having to subject animals to potentially lethal stress, hereby reducing some ethical concerns of animal suffering and the results thereof, without compromising accuracy. Lethal trapping is also often more economical and practical, further favoring this collection method.

High-elevational occurrence of two tick species, Ixodes ricinus and I. trianguliceps, at their northern distribution range

“…Lethal traps were baited with peanut butter for practical reasons as it is easily applied to the inside of the trap body. Trap type does not influence tick burden size on the captured animals [ 60 ]. At each altitude, the live and lethal plots were placed at approximately 100 m distance from each other, but in locations with similar vegetation structure and habitat characteristics.…”

Individual heterogeneity in ixodid tick infestation and prevalence of Borrelia burgdorferi sensu lato in a northern community of small mammalian hosts

“…3). These two trap types had no measurable impact on tick infestation in a study on this specific topic (De Pelsmaeker et al 2020 ), and we found no measurable effects of whether the animal was found alive or dead in a supporting analysis detailed in the appendices (Table S6). Each of the four trap stations at each trapping site consisted of either 1 cage trap or 3 snap traps (to avoid trap saturation) in a triangle formation.…”

Host in reserve: The role of common shrews (Sorex araneus) as a supplementary source of tick hosts in small mammal communities influenced by rodent population cycles

“…The other plot was equipped with lethal traps (Rapp2 Mousetrap, http://www.rappfellene.no), and baited with peanut butter. A previous study has shown that both trap types perform similarily in terms of trapping efficiency and tick burdens (De Pelsmaeker et al, 2020). Humidity and temperature were recorded at station level every hour for the duration of the trapping period, using a TinyTag Plus 2 – TGP 4017 datalogger, housed in a DataMate instrument cover ACS‐5050, mounted approximately 50 cm aboveground level.…”