Decreased small mammal and on-host tick abundance in association with invasive red imported fire ants (Solenopsis invicta).

Adrian A Castellanos,Michael E Morrow,Pete D Teel,Gabriel L Hamer,Micky D Eubanks,Sarah A Hamer,Matthew C I Medeiros,Jessica E Light

doi:10.1098/rsbl.2016.0463

Adrian A Castellanos, Michael E Morrow + Show 6 more

Open Access

https://doi.org/10.1098/rsbl.2016.0463

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Abstract

Invasive species may impact pathogen transmission by altering the distributions and interactions among native vertebrate reservoir hosts and arthropod vectors. Here, we examined the direct and indirect effects of the red imported fire ant (Solenopsis invicta) on the native tick, small mammal and pathogen community in southeast Texas. Using a replicated large-scale field manipulation study, we show that small mammals were more abundant on treatment plots where S. invicta populations were experimentally reduced. Our analysis of ticks on small mammal hosts demonstrated a threefold increase in the ticks caught per unit effort on treatment relative to control plots, and elevated tick loads (a 27-fold increase) on one common rodent species. We detected only one known human pathogen (Rickettsia parkeri), present in 1.4% of larvae and 6.7% of nymph on-host Amblyomma maculatum samples but with no significant difference between treatment and control plots. Given that host and vector population dynamics are key drivers of pathogen transmission, the reduced small mammal and tick abundance associated with S. invicta may alter pathogen transmission dynamics over broader spatial scales.

Highlights

Invasive species can directly or indirectly alter vector-borne disease systems by changing the abundance of, or interactions between, vectors and their hosts
This suggests that the effect of a greater number of on-host ticks on treatment plots was primarily driven by an increased capture rate of small mammals along treatment transects
To directly investigate tick loads across treatment and control plots, we modelled the number of ticks per host individual in S. hispidus and R. fulvescens, two well-sampled (N 1⁄4 482 and 195, respectively) and highly parasitized species in our data

Summary

Introduction

Invasive species can directly or indirectly alter vector-borne disease systems by changing the abundance of, or interactions between, vectors and their hosts. Previous studies have most commonly implicated the invader in altering species relationships in ways that support vector-borne pathogen transmission and, increase disease risk. A widespread, invasive shrub increases human risk of ehrlichiosis because it provides habitat for deer that host infected ticks [1], and densities of ticks and tick hosts were greatest in areas that had been invaded by the causative agent of sudden oak death [2]. [3]), invasive species have less frequently been implicated in the reduction of infectious disease transmission. Invasive host species may dilute vector-borne disease risk consistent with the dilution effect hypothesis [4].

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