Establishing a reference interval for acute phase proteins, cytokines, antioxidants and commonly measured biochemical and hematologic parameters in the northern fur seal (Callorhinus ursinus)

Abstract

Over the past several decades there has been a precipitous decline of northern fur seals (Callorhinus ursinus; NFS) at their breeding grounds on the Pribilof Islands in the Bering Sea. The cause of this decline is likely multifactorial and could include changes in environmental parameters, prey abundance and distribution as well as exposure to pathogens and pollutants. Evaluation of inflammatory markers and antioxidant levels of the current population of fur seals in addition to hematologic and biochemical profiles could provide important information regarding health and subclinical or clinical disease in this population. Serum and plasma samples were obtained from clinically healthy adult female NFS and references intervals were determined for multiple parameters that can be altered in response to the presence of disease and environmental stressors. We established a reference interval for cytokines involved in acute inflammation and infection (TNFa, IL1, IL6, IL8, KC, IL10, C-reactive Protein) by utilizing commercially available canine cross-reactive antibodies. Reference intervals were also established for reactive oxygen species (hydrogen peroxide and malondialdehyde), as well as antioxidant levels (vitamin E and selenium) and acute phase proteins evaluated by serum electrophoresis. To improve the ability to compare and interpret indicators of health and disease in this species, we developed reference intervals for commonly utilized hematologic and biochemical tests in addition to the aforementioned markers of oxidative stress and inflammatory biomarkers. There were several animals identified as outliers indicating that they may have had subclinical illness or inflammation. Further investigation utilizing these tests in clinically ill animals and comparison to animals that exhibit normal behavior and no overt signs of illness could increase our understanding of the utility of measuring these parameters in this species.