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Open Access Highly Accessed Research article

Evaluation of immune and stress status in harbour porpoises (Phocoena phocoena): can hormones and mRNA expression levels serve as indicators to assess stress?

Sabine Müller1, Kristina Lehnert12, Henrike Seibel1, Jörg Driver3, Katrin Ronnenberg1, Jonas Teilmann4, Cornelius van Elk5, Jakob Kristensen6, Eligius Everaarts7 and Ursula Siebert1*

Author Affiliations

1 Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Foundation, Büsum 25761, Germany

2 Institute for Coastal Research, Helmholtz-Zentrum Geesthacht, Geesthacht 21502, Germany

3 Veterinary Clinic, Reinsbüttel 25764, Germany

4 Departement of Bioscience, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark

5 Dolfinarium Harderwijk, Strandboulevard Oost 1, Harderwijk, AB 3841, The Netherlands

6 Fjord and Belt, Margrethes Plads 1, Kerteminde 5300, Denmark

7 SOS Dolfijn, Strandboulevard Oost 1, Harderwijk, AB 3841, The Netherlands

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BMC Veterinary Research 2013, 9:145  doi:10.1186/1746-6148-9-145

Published: 17 July 2013

Abstract

Background

The harbour porpoise is exposed to increasing pressure caused by anthropogenic activities in its marine environment. Numerous offshore wind farms are planned or under construction in the North and Baltic Seas, which will increase underwater noise during both construction and operation. A better understanding of how anthropogenic impacts affect the behaviour, health, endocrinology, immunology and physiology of the animals is thus needed. The present study compares levels of stress hormones and mRNA expression of cytokines and acute-phase proteins in blood samples of harbour porpoises exposed to different levels of stress during handling, in rehabilitation or permanent human care.

Free-ranging harbour porpoises, incidentally caught in pound nets in Denmark, were compared to harbour porpoises in rehabilitation at SOS Dolfijn in Harderwijk, the Netherlands, and individuals permanently kept in human care in the Dolfinarium Harderwijk and Fjord & Belt Kerteminde, Denmark. Blood samples were investigated for catecholamines, adrenaline, noradrenaline and dopamine, as well as for adrenocorticotropic hormone (ACTH), cortisol, metanephrine and normetanephrine. mRNA expression levels of relevant cell mediators (cytokines IL-10 and TNFα, acute-phase proteins haptoglobin and C-reactive protein and the heat shock protein HSP70) were measured using real-time PCR.

Results

Biomarker expression levels varied between free-ranging animals and porpoises in human care. Hormone and cytokine ranges showed correlations to each other and to the health status of investigated harbour porpoises. Hormone concentrations were higher in free-ranging harbour porpoises than in animals in human care. Adrenaline can be used as a parameter for the initial reaction to acute stress situations; noradrenaline, dopamine, ACTH and cortisol are more likely indicators for the following minutes of acute stress. There is evidence for different correlations between production of normetanephrine, metanephrine, cortisol and the expression of IL-10, HSP70 and haptoglobin.

Conclusions

The expression patterns of the selected molecular biomarkers of the immune system are promising to reflect the health and immune status of the harbour porpoise under different levels of stress.

Keywords:
Harbour porpoise; Stress hormones; Cytokines; Anthropogenic impact; Offshore wind farms; Underwater noise