Abstract

The exact causes of and factors contributing to marine mammal strandings are not always fully understood. Efforts expended in rehabilitation of these animals are considerable, yet the access to state of the art diagnostic and prognostic tools is rather limited. The present study proposes to evaluate the value of immune function tests as diagnostic and prognostic aids in the health assessment (and follow up) of stranded marine mammals. To do this, a battery of immune function tests that have been validated in marine mammals was performed, in parallel with and independently from the regular medical evaluation of stranded marine mammals (including physical examination, hematology, serum chemistry, and any other test judged appropriate). Correlations between the results of immune assays with the medical records and outcome of the rehabilitation efforts (release vs. death) were performed to assess the clinical value of those immune tests. Results of the first of two years of testing suggest that while some trends between immune functions and leukocyte counts were quite obvious in particular situations, no general trend was observed that remained constant in time and between individuals. Anecdotally, phagocytosis and respiratory burst often appear to vary in opposite directions. The termination of antibiotic therapy did not result in consistent modulation of the immune functions tested. The odds of "abnormal" values for immune functions (based on mean +/- 1, 1.5 or 2 SD in our dataset) were calculated as the ratio of the frequency (%) of values outside the confidence interval in samples in which WBC values were abnormal compared to when WBC values were normal. In both grey and harp seals, high WBC appeared to increase the odds of "abnormal" innate immune functions (phagocytosis and respiratory burst) as well as B cell proliferation. This is not surprising, as innate immune functions represent the first line of defense to insults such as bacterial infections, while a B cell-mediated antibody response is the hallmark of the acquired immune response to extra-cellular pathogens such as most bacteria. Overall, the findings of blind immunological testing are compatible with known general response patterns to different types of insults. While immune function assays have not yet been fully validated as diagnostic tests, analysis of the results from a second season of testing will allow further refinement of these results and an assessment of the value of different immune parameters in health assessment.