Effects of urbanization on host-pathogen interactions, using Yersinia in house sparrows as a model.

Lieze Oscar Rouffaer,Noraine Salleh Hudin,Frank Pasmans,Michel Delmée,Aimeric Teyssier,Luc Lens,An Martel,Ivo Cox,Freddy Haesebrouck,Roel Haesendonck,Diederik Strubbe,Anne-Marie Van Den Abeele

doi:10.1371/journal.pone.0189509

Abstract

Urbanization strongly affects biodiversity, altering natural communities and often leading to a reduced species richness. Yet, despite its increasingly recognized importance, how urbanization impacts on the health of individual animals, wildlife populations and on disease ecology remains poorly understood. To test whether, and how, urbanization-driven ecosystem alterations influence pathogen dynamics and avian health, we use house sparrows (Passer domesticus) and Yersinia spp. (pathogenic for passerines) as a case study. Sparrows are granivorous urban exploiters, whose western European populations have declined over the past decades, especially in highly urbanized areas. We sampled 329 house sparrows originating from 36 populations along an urbanization gradient across Flanders (Belgium), and used isolation combined with ‘matrix-assisted laser desorption ionization- time of flight mass spectrometry’ (MALDI-TOF MS) and PCR methods for detecting the presence of different Yersinia species. Yersinia spp. were recovered from 57.43% of the sampled house sparrows, of which 4.06%, 53.30% and 69.54% were identified as Y. pseudotuberculosis, Y. enterocolitica and other Yersinia species, respectively. Presence of Yersinia was related to the degree of urbanization, average daily temperatures and the community of granivorous birds present at sparrow capture locations. Body condition of suburban house sparrows was found to be higher compared to urban and rural house sparrows, but no relationships between sparrows’ body condition and presence of Yersinia spp. were found. We conclude that two determinants of pathogen infection dynamics, body condition and pathogen occurrence, vary along an urbanization gradient, potentially mediating the impact of urbanization on avian health.

Highlights

With growing human populations, cities are expanding rapidly and urbanization represents one of the most intense anthropogenic modifications of natural systems, strongly affecting species, communities and ecosystems [1,2]
Other than Y. enterocolitica and Y. pseudotuberculosis were isolated from 41% (134/329) of the house sparrows
A high prevalence of Yersinia was demonstrated in the faeces of the examined house sparrows, of which most isolates belonged to Y. enterocolitica and only a small percentage to Y. pseudotuberculosis

Summary

Introduction

Cities are expanding rapidly and urbanization represents one of the most intense anthropogenic modifications of natural systems, strongly affecting species, communities and ecosystems [1,2]. The direction and strength of responses of bird species to urbanization is function of their life-history strategies [3]. This has led to the ‘biotic homogenization’ of urban bird communities [4], i.e. whereby the latter become gradually dominated by a limited number of ‘urban exploiter’ species, such as house sparrows (Passer domesticus) [5]. Several authors have addressed the effects of urbanization on avian stress levels and body condition How urbanization affects disease ecology, wildlife-pathogen interactions and animal health remains underexplored, despite its potential effect on ecological and evolutionary mechanisms driving population dynamics [12,13,14,15,16]. The potential existence of subclinical effects on avian health and body condition remains a gap in our knowledge

Methods

Results

Conclusion