Haemosporidian infections affect antioxidant defences in great tits Parus major but are not related to exposure to aerial pollutants

Daniela De Angeli Dutra,Patrícia Silveira,José Paulo Sousa,Érika Martins Braga,Ana Cláudia Norte,Jaime Albino Ramos

doi:10.1017/pao.2017.4

Daniela De Angeli Dutra, Patrícia Silveira + Show 4 more

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https://doi.org/10.1017/pao.2017.4

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Abstract

SUMMARY Haemosporidian parasites are widespread in avian species and modulate their ecology, behaviour, life-history and fitness. The prevalence of these vector-transmitted parasites varies with host intrinsic and extrinsic factors, such as host resistance and behaviour, and habitat-related characteristics. In this study, we evaluated the prevalence of avian haemosporidians in great tit Parus major populations inhabiting two areas with different degrees of exposure to aerial emissions from pulp mills, to assess if this type of pollution impacted parasite prevalence. We also compared the physiological condition of infected and uninfected individuals. Haemosporidian infection prevalence was high (58%), varied seasonally, but was not associated with air pollution exposure. Fledged birds presented higher infection rates than nestlings and infected fledged birds had higher levels of blood glutathione peroxidase activity. These results allow us to infer that infection by blood parasites may activate antioxidant defences, possibly to protect the organism from the negative oxidative stress side-effects of immune activation against parasites. Because oxidative stress is one of the mechanisms responsible for ageing and senescence and may affect fitness, the relationship between parasitism and oxidative stress markers should be further investigated through studies that include experimental manipulation of infection in model organisms.

Highlights

Environmental degradation and presence of pollutants are likely to negatively impact wildlife
We assessed the effects of haemosporidian infection on great tit physiology, namely on haematological, biochemical and morphological parameters, and whether their infection status was related with their ectoparasite levels
We evaluated how infection by haemosporidians in fledged birds was affected by intrinsic and extrinsic factors using Generalized Linear Models, with binomial distributions and logit link function

Summary

Introduction

Environmental degradation and presence of pollutants are likely to negatively impact wildlife. Apart from their direct effect, pollutants may affect the organism susceptibility to infection through direct immunotoxic effects (by interfering with immune receptor binding and triggering inappropriate and/ or inhibiting immune responses), or through an increase of the overall stress levels of the organism which may lead to immunossupression (Dobson and Foufopoulos, 2001; Martin and Boruta, 2014). Grasman et al (1996) reported that fish-eating birds exposed to polyclorinated byphenyls showed inhibited T- cell mediated immunity, which might have been the cause for a high incidence of bacterial infections in these high trophic level birds. We assessed the effect of environmental pollution (aerial emissions from pulp mills) on the prevalence of haemosporidians in those great tit populations. Haemosporidians are ubiquitous microscopic parasitic protozoa in birds, infecting blood cells and tissues and transmitted by blood-sucking insect vectors of the order Diptera (Valkiūnas, 2005)

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