Otostrongylus circumlitis (OC), a nematode lungworm, accounts for 37% of northern elephant seal (NES; Mirounga angustirostris) mortalities at The Marine Mammal Center (TMMC, Sausalito, CA).1 The current lack of specific antemortem diagnostic tests for pre-patent OC infection in NES makes identifying cases, treating infections, and assessing efficacy of treatment challenging.2 Once clinical signs develop, severe inflammation and disseminated intravascular coagulation (DIC) develop rapidly and are difficult to treat.2 Recent studies have evaluated the use of blood inflammatory and coagulation pathway biomarkers in early diagnosis.2-4 The objective of this study was to investigate the diagnostic performance of a suite of clinicopathologic tests (hematology, plasma biochemistry, protein electrophoresis, serum amyloid-A (SAA), C-reactive protein, and coagulation parameters) for diagnosis of OC clinical infections in NES. Samples from nine NES with OC infection confirmed by gross pathology with blood collected antemortem during clinical disease and 20 NES initially admitted for malnutrition and sampled shortly before release after successful rehabilitation were included in the study. Using receiver operator characteristic (ROC) curve analysis, the diagnostic performance of albumin:globulin ratio, SAA, platelet count, activated partial thromboplastin time, and prothrombin was high (i.e., area under curve (AUC) >0.9). These results indicate systemic inflammation and DIC, and support previously reported pathologic findings in NES infected with OC.2-4 In addition to AUC values, this study produced cut-off points, sensitivity, specificity, and predictive values for analytes with high diagnostic performance. This data will be useful in clinical management and will aid in assessment of treatment efficacy in infected NES.
The authors thank the veterinary and husbandry volunteers and staff at TMMC for caring for these animals and collecting samples, the research staff at TMMC for organizing and shipping samples. The authors also thank Dr. Carolyn Cray and the University of Miami Acute Phase Protein Laboratory for performing protein assays.
1. Colegrove KM, Greig DJ, Gulland FMD. Causes of live strandings of northern elephant seals (Mirounga angustirostris) and Pacific harbor seals (Phoca vitulina) along the central California coast, 1992–2001. Aquat Mammals. 2005;31(1):1–10.
2. Gulland FM, Beckmen K, Burek K, Lowenstein L,Werner L, Spraker T, Dailey M, Harris E. Nematode (Otostrongylus circumlitis) infestation of Northern elephant seals (Mirounga angustirostris) stranded along the central California coast. Mar Mamm Sci. 1997;13(3):446–459.
3. Kaye S, Johnson S, Rios C, and Fletcher DJ. Plasmatic coagulation and fibrinolysis in healthy and Otostrongylus-affected Northern elephant seals (Mirounga angustirostris). Vet Clin Pathol, 2017;46:589–596.
4. Sheldon JD, Johnson SP, Hernandez JA, Cray C, Stacy NI. Acute-phase responses in healthy, malnourished, and Otostrongylus-infected juvenile northern elephant seals (Mirounga angustirostris). J Zoo Wildl Med. 2017;48(3):767–775.