Sampling scale and season influence the observed relationship between the density of deer and questing Ixodes ricinus ny
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(2020) 13:493 Dickinson et al. Parasites Vectors https://doi.org/10.1186/s13071-020-04369-8
Open Access
RESEARCH
Sampling scale and season influence the observed relationship between the density of deer and questing Ixodes ricinus nymphs Eleanor R Dickinson1,2,3*, Caroline Millins1,4 and Roman Biek1
Abstract Background: The relationship between environmentally transmitted tick parasites, Ixodes spp., and their main reproductive host, deer, is generally thought to be positive. However, measuring host abundance and density directly can be challenging and indirect methods are often used. The observed relationship between the parasite and host may be affected by sampling scale and season, which could lead to different inferences being made. Here, we aimed to test the effect of sampling scale and season on the relationship between density of deer and the density of questing Ixodes ricinus nymphs. Methods: The density of deer (primarily Dama dama) was estimated using line transect distance sampling of deer dung quantified in different seasons (winter and summer) and measured at three different nested scales (site, transect and observation level). Questing nymph density was measured using blanket drag methods and estimates were calculated at the same scales as deer density estimates. General linear models were used to evaluate the relationship between questing nymphs, deer density and other environmental variables at each sampling scale and each season deer density was measured at. Results: While a positive relationship between deer density and questing nymph density was detected at the site and transect scale, no relationship was apparent at the observation level. This was likely due to increased variation and reduced precision of deer dung counts at the finest sampling scale. Seasonal changes in deer populations were observed likely reflecting seasonal shifts in habitat usage. The summer estimates of deer density explained questing nymph density whereas winter estimates did not. Conclusions: Our results show that the scale of sampling can affect the detectability of the positive association between host and vector species. Furthermore, such associations can be obscured if hosts exhibit seasonal changes in habitat use. Thus, both sampling scale and season are important to consider when investigating the relationship between host and vector species. Keywords: Tick, Parasite host relationship, Spatial distribution, Deer density, Fallow deer, Distance sampling Background The distribution and abundance of parasites is expected to be highly dependent on host abundance, density and *Correspondence: [email protected] 1 Institute of Biodiversity, Animal Health and Comparative Medicine, Graham Kerr Building, University of Glasgow, 82 Hillhead St, Glasgow G12 8QQ, Scotland, UK Full list of author information is available at the end of the article
space use [1, 2]. In the Northern hemisphere Ixodes ricinus are vectors for multiple pathogens important for animal and human health such as Borrelia burgdorferi (sensu la
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