Investigation of the Use of Biomarkers for Antemortem Diagnosis of Cardiac Disease in Marine Mammals
Cardiac pathology, though extensively documented in marine mammals;1-5 remains difficult to diagnose ante-mortem. Cardiac troponin I (cTnI) and N-terminal pro-brain natriuretic peptide (proBNP) are used in many species as sensitive and specific biomarkers for a range of cardiac diseases. This study aimed to determine whether cTn and/or proBNP were increased in confirmed cases of cardiac disease in beluga whales (BW) (Delphinapterus leucas), sea otters (SO) (Enhydra lutris), Steller sea lions (SSL) (Eumetopias jubatus), and California sea lions (CSL) (Zalophus californianus), compared to controls. Existing immunoassays for cTnI and proBNP were validated utilizing species-specific heart lysate spiked serum. Banked serum samples from animals with confirmed cardiac disease on histopathology (disease: BW n=3, SO n=4, SSL n=4, CSL n=19), and animals with no evidence of cardiac disease (control: BW n=5, SO n=2, SSL n=6, CSL n=6) were analyzed. Serum concentrations of cTnI (ng/ml) and proBNP (pmol/L) ranged as follows: BW: cTnI <0.03–21.06, proBNP <200; SO: cTnI <0.03–0.24, proBNP <200; SSL: cTnI <0.03–12.14, proBNP <200–1,783; CSL: cTnI <0.03–44.5, proBNP <200–1,871. Preliminary statistics revealed significantly higher proBNP in diseased CSL (Mann Whitney U test; p=0.017), and a trend toward higher cTnI in diseased SO (Mann Whitney U test; p=0.06). Higher cTnI in diseased animals was seen in other species; however, due to the presence of outliers statistical significance cannot be confirmed. Results suggest that proBNP and cTnI may be clinically useful as ante-mortem diagnostic tools in CSL and SO, respectively. Increasing sample size and further investigation regarding disease severity is warranted and in process.
The authors thank the Wild Animal Health Fund (WAHF) for providing generous funding for this project. We would also like to thank Sion Cahoon and Dr. Martin Haulena from Vancouver Aquarium, Barbie Halaska and Dr. Cara Field from The Marine Mammal Center, Natalie Rouse and Dr. Carrie Goertz from Alaska Sea Life Center, and Gayle Sirpenski from Mystic Aquarium for their support and invaluable contributions to this study.
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