Higher plasma corticosterone is associated with reduced costs of infection in red-winged blackbirds

Schoenle, Laura A.; Schoepf, Ivana; Weinstein, Nicole; Moore, Ignacio T.; Bonier, Frances

doi:10.1016/j.ygcen.2017.07.006

Cited by 11 publications

(19 citation statements)

References 101 publications

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“…Seven days after implantation, birds in the high-dose implant group had corticosterone concentrations of (mean + s.e.) 8.79 + 1.89 ng ml 21 , which is similar to concentrations in free-living, breeding males, which we previously measured as 12.31 + 1.86 ng ml 21 [13]. Across all treatments, the change in corticosterone from the initial value decreased over time, indicating a waning effect of the implants or upregulated negative feedback and clearance mechanisms (F ¼ 14.66, p ¼ 0.0002).…”

Section: Results (A) Effectiveness Of Corticosterone Treatmentsupporting

confidence: 77%

“…In our previous field study of red-winged blackbirds, higher endogenous plasma corticosterone concentrations were associated with maintaining higher haematocrit for a given parasite burden [13]. In the present study, exogenous corticosterone treatment had no effect on tolerance when measured using haematocrit or haemoglobin and instead reduced tolerance as estimated with body mass.…”

Section: Discussioncontrasting

confidence: 46%

“…Dissimilarities between natural and captive environments, or the effects of manipulated, exogenous hormone concentrations and endogenous hormone concentrations, could contribute to the contrasting outcomes observed here and in the prior field study [13]. Physiological responses to stimuli can vary in captive and wild settings [68,69].…”

Section: Discussionmentioning

confidence: 94%

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Exogenous glucocorticoids amplify the costs of infection by reducing resistance and tolerance, but effects are mitigated by co-infection

et al. 2019

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Individual variation in parasite defences, such as resistance and tolerance, can underlie heterogeneity in fitness and could influence disease transmission dynamics. Glucocorticoid hormone concentrations often change in response to fluctuating environmental conditions and mediate changes in immune function, resource allocation and tissue repair. Thus, changes in glucocorticoid hormone concentrations might mediate individual variation in investment in resistance versus tolerance. In this study, we experimentally increased glucocorticoid concentrations in red-winged blackbirds ( Agelaius phoeniceus ) that were naturally infected with haemosporidian parasites, and assessed changes in resistance and tolerance of infection. Glucocorticoid treatment increased burdens of Plasmodium , the parasite causing avian malaria, but only in the absence of co-infection with another Haemosporidian, Haemoproteus . Thus, glucocorticoids might reduce resistance to infection, but co-infection can mitigate the negative consequences of increased hormone concentrations. Glucocorticoid treatment also decreased tolerance of infection. We found no evidence that the inflammatory immune response or rate of red blood cell production underlie the effects of glucocorticoids on resistance and tolerance. Our findings suggest that exogenous glucocorticoids can increase the costs of haemosporidian infections by both increasing parasite numbers and reducing an individual's ability to cope with infection. These effects could scale up to impact populations of both host and parasite.

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Section: Results (A) Effectiveness Of Corticosterone Treatmentsupporting

confidence: 77%

Section: Discussioncontrasting

confidence: 46%

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Exogenous glucocorticoids amplify the costs of infection by reducing resistance and tolerance, but effects are mitigated by co-infection

et al. 2019

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“…We captured 29 adult male red‐winged blackbirds in April–May 2015 using mist nets with a conspecific playback and decoy or a seed‐baited Troyer V‐top trap at the Queen's University Biological Station (44°34′02.3″ N, 76°19′28.4″ W) and on nearby private property in Elgin, Ontario (44°36′28.8″ N, 76°13′38.3″ W). This population has been known to have high prevalence of haemosporidian infection since the late 1980s (Weatherhead, ; Weatherhead & Bennett, ; Weatherhead, Metz, Bennett, & Irwin, ) and from 2013 to 2015, prevalence was over 90% (Schoenle, Schoepf, Weinstein, Moore, & Bonier, ). We housed birds at the Queen's University Biological Station in semi‐natural conditions using an outdoor aviary consisting of 30 large flight aviaries (6 × 2.5 × 2.5 m) with walls that were permeable to insects, including potential vectors of Haemosporida.…”

Section: Methodsmentioning

confidence: 99%

An experimental test of the physiological consequences of avian malaria infection

Schoenle

Kernbach

Haussmann

et al. 2017

Journal of Animal Ecology

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Chronic, low-intensity parasite infections can reduce host fitness through negative impacts on reproduction and survival, even if they produce few overt symptoms. As a result, these parasites can influence the evolution of host morphology, behaviour and physiology. The physiological consequences of chronic infection can provide insight into the processes underlying parasite-driven natural selection. Here, we evaluate the physiological consequences of natural, low-intensity infection in an avian host-parasite system: adult male red-winged blackbirds (Agelaius phoeniceus) infected with haemosporidian parasites. Chronic haemosporidian infection has previously been shown to reduce both reproductive success and survival in several avian species. We used antimalarial medications to experimentally reduce haemosporidian parasitaemia (the proportion of blood cells infected with haemosporidian parasites) and measured the effect of treatment on body condition, haematology, immune function, physiological stress and oxidative state. Treatment with an antimalarial medication reduced parasitaemia for the most prevalent haemosporidian parasites from the genus Plasmodium. Treatment also increased haemoglobin and haematocrit, and decreased red blood cell production rates. We detected no effect of treatment on body condition, immune metrics, plasma corticosterone concentrations, total antioxidant capacity or reactive oxygen metabolites. Our results suggest that the damage and replacement of red blood cells during infection could be important costs of chronic haemosporidian infection. Strong links between parasitaemia and the physiological consequences of infection indicate that even for relatively low-intensity infections, measuring parasitaemia rather than only presence/absence could be important when evaluating the role of infection in influencing hosts' behaviour, physiology or fitness.

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“…haematocrit, baseline and stress-induced corticosterone) differences between infected and uninfected birds. Some studies, also in natural population, have investigated the association between physiological variables and blood parasite infection, and they produced mixed results: blood parasite infection was associated with detrimental effects on physiology in some but not all studies [20,80,[84][85][86][87][88][89].…”

Section: Relationships Between Parasite Infection and Physiologymentioning

confidence: 99%

Physiological and morphological correlates of blood parasite infection in urban and non-urban house sparrow populations

Bichet¹,

Brischoux²,

Ribout³

et al. 2020

PLoS ONE

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In the last decade, house sparrow populations have shown a general decline, especially in cities. Avian malaria has been recently suggested as one of the potential causes of this decline, and its detrimental effects could be exacerbated in urban habitats. It was initially thought that avian malaria parasites would not have large negative effects on wild birds because of their long co-evolution with their hosts. However, it is now well-documented that they can have detrimental effects at both the primo-and chronical infection stages. In this study, we examined avian malaria infection and its physiological and morphological consequences in four populations of wild house sparrows (2 urban and 2 rural). We did not find any relationship between the proportions of infected individuals and the urbanisation score calculated for our populations. However, we observed that the proportion of infected individuals increased during the course of the season, and that juveniles were less infected than adults. We did not detect a strong effect of malaria infection on physiological, morphological and condition indexes. Complex parasite dynamics and the presence of confounding factors could have masked the potential effects of infection. Thus, longitudinal and experimental studies are needed to understand the evolutionary ecology of this very common, but still poorly understood, wild bird parasite.

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Higher plasma corticosterone is associated with reduced costs of infection in red-winged blackbirds

Cited by 11 publications

References 101 publications

Exogenous glucocorticoids amplify the costs of infection by reducing resistance and tolerance, but effects are mitigated by co-infection

Exogenous glucocorticoids amplify the costs of infection by reducing resistance and tolerance, but effects are mitigated by co-infection

An experimental test of the physiological consequences of avian malaria infection

Physiological and morphological correlates of blood parasite infection in urban and non-urban house sparrow populations

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