Discrepancy of Plasma Iron Concentrations with Tissue Iron Stores in Chronically Debilitated Loggerhead Sea Turtles (Caretta caretta) with Inflammatory Disease
Abstract
Debilitated loggerhead sea turtles present with emaciation, anemia, hypoproteinemia, parasitism, septicemia, and systemic inflammation.1-3 Systemic inflammation and starvation cause iron sequestration in tissue macrophages and hepatocytes, and significantly affect plasma protein concentrations, including iron-binding and -transporting proteins.4-6 Plasma iron is currently the only available, non-invasive diagnostic test to assess the iron status in non-mammalian vertebrates, because other assays (e.g., ferritin) require species-specific reagents. However, plasma iron alone does not necessarily reflect tissue iron stores.5 The objective of this study was to compare plasma iron with tissue iron concentrations in anemic loggerhead sea turtles (Caretta caretta). Blood from five stranded debilitated loggerhead sea turtles was collected upon admission. All turtles had severe nonregenerative anemia (PCV range 4–8%), evidence of systemic inflammation (heterophilia, left-shifting, and/or heterophil toxicity), and died before any treatment was administered. Plasma iron concentrations were compared with Prussian blue-stained sections of liver, spleen, and bone marrow evaluated morphometricallya for semiquantification of iron. Plasma iron was low (range 11–32 μg/dl) in all five patients. All turtles had hepatic hemosiderosis confirmed by Prussian blue staining. Spleen and bone marrow had negligible amounts of iron by histopathology and morphometry. There was no correlation between plasma iron concentrations and hepatic iron stores, likely caused by a hypoferremia associated with inflammatory disease and hypoproteinemia. Our findings indicate that plasma iron correlates poorly with body iron stores in debilitated loggerhead sea turtles, similar to mammals with systemic inflammation. Since excess iron administration reportedly can cause adverse effects,6 iron supplementation should be carefully considered in anemic sea turtles with suspected inflammatory disease, as these patients have ample hepatic iron stores and additional administration may cause further compromise.
Endnote
a. ImagePro® Analyzer v 7.0
Acknowledgements
The authors would like to thank Abbie Butler and Lucy Dalton, University of Georgia, Histology Laboratory, for processing tissue sections for Prussian blue. We are grateful for all the hard work of all members of the sea turtle stranding network.
* Presenting author
+ Student presenter
Literature Cited
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