DOI: 10.5061/dryad.d7wm37q9d
title: Data from: The release of non-native gamebirds is associated with amplified zoonotic disease risk

description: Spillback – where non-native species increase native pathogen prevalence –
 is potentially an important mechanism by which non-natives contribute to
 zoonotic disease emergence. However, spillback has not yet been directly
 demonstrated because it is difficult to disentangle from confounding
 factors which correlate with non-native species abundance and native
 pathogen prevalence. Here, we capitalise on replicated, quasi-experimental
 releases of non-native pheasants (Phasianus colchicus) to compare vector
 abundance and native pathogen prevalence between sites with similar local
 conditions but different non-native densities. Prevalence of Borrelia sp.
 (the causative agent of Lyme disease) in questing ticks was almost 2.5x
 higher in woods where pheasants are released compared to control woods,
 with a particularly strong effect on Borrelia garinii, a bird specialist
 genospecies. Furthermore, adult (but not nymphal) ticks tended to be more
 abundant at pheasant-release woods. This work provides evidence that
 non-native species can impact zoonotic pathogen prevalence via spillback
 in ecologically relevant contexts.
description: # Data from: The deliberate release of a non-native species amplifies
 zoonotic disease risk via spillback
 [https://doi.org/10.5061/dryad.d7wm37q9d](https://doi.org/10.5061/dryad.d7wm37q9d) Code can be found in the 'related works' box on right of the DRYAD landing page. Or via the DOI [https://doi.org/10.5281/zenodo.13919564](https://doi.org/10.5281/zenodo.13919564 "Go to software") ## Description of the data and file structure *I.ricinus* tick abundance and *Borrelia* prevalence data from 89 woods across the southwest of England. Including woods in which pheasants were released, and woods in which pheasants were not released. ### Files and variables #### File: distance\_matrix.csv **Description:** pairwise distances for the 25 shoots included in the present study. #### File: tick\_abundance\_2024.csv **Description:** ##### Variables * area: a unique identity number attributed to each shoot * edge: distance from woodland edge, either 'interior' (-0.5) or 'edge' (0.5) * temp: temperature, already scaled * tree_sp: the species of the tree closest to a given transect * herb_sp: the most common under-story plant species during a transect * herb_sp2: the second most common under-story plant species during a transect * bare: % cover of bare-ground during a transect * n: tick nymph count on a given transect * a: adult tick count on a given transect * size: the area of a wood in meters squared, scaled to have a mean of 0 and sd of 1 * xcoord: longitudinal coordinate of a given shoot * ycoord: latitudinal coordinate of a given shoot * id: a unique identity number attributed to each transect (referred to in the main text as a 'drag') * dys3: date, the number of days since the first survey day, scaled to vary from 0 to 1, where 1 is the last day of surveying and 0 the first. * depth_scaled: vegetation depth, already scaled * rank: a unique identity number attributed to each wood * tr: pheasant-release, 0.5 is attributed to each transect conducted in a wood where pheasants are released, -0.5 for each transect conducted where pheasants are not released. * cn: conifer, 0.5 is attributed to each transect where the nearest tree species is was broadleaf, -0.5 where the nearest tree species is was conifer. * pheas_scale: the number of pheasants released, scaled to have a standard deviation of 1 and a mean of 0 #### File: tick\_borrelia.sp\_prev.csv **Description:** borrelia sp. infection status for all ticks sampled in this study ##### Variables * edge: distance from woodland edge, either 'interior' (2), or 'edge' (1) * size : the area of a wood in meters squared * area: a unique identitiy number attributed to each shoot * pos: Borrelia positive, tick from positive pools are attributed '1' * treat: pheasant-release, 2 is attributed to ticks collected from wood where pheasants are released, 1 to ticks collected from woods where pheasants are not released. * adult: tick life stage, nymphs = 1, adults = 2 * sday: julian day scaled to have a standard deviation of 1 and mean of 0. * pheas_standard: The number of pheasants released at a shoot, scaled to have a mean of 0 and standard deviation of 1. * rank: a unique identitiy number attributed to each wood * iii: a code fed into missclassification models, 1 for negative ticks were borrelia screened individually, 2 for positive ticks screened infividually, 3 for negative ticks screened with another tick, and 4 for positive ticks screened with another tick. #### File: tick\_borrelia.sp\_broadleaf\_prev.csv **Description:** as above but also including: ##### Variables * per_cent_broadleaf: percentage of trees in a given wood which were broadleaf, expressed as a ratio #### File: tick\_borrelia\_genospecies\_prev.csv **Description:** as above but also including: ##### Variables * best_match: borrelia genospecies 1 = garinii, 2 = afzelii, 3 = valaisiana, 4 = undescribed/finlandensis, 5 = unresolved ## Code/software Analysis is conducted using R versions 4+. Models are built using the packages 'rethinking' and 'brms' which are wrappers for the free statistics program 'Stan'. Installation instructions can be found in the markdown file as well as a list of any other required packages.