A RETROSPECTIVE ANALYSIS OF MORBIDITY AND MORTALITY IN NORTHERN FUR SEALS (CALLORHINUS URSINUS) IN UNITED STATES AQUARIA FROM 1976-2022.

Abstract

Pathology of wild northern fur seals (NFS) (Callorhinus ursinus) is well documented; however, data on NFS under professional care are limited. The objective of this retrospective study was to evaluate causes of morbidity and mortality in 67 NFS housed in long-term professional care in United States aquaria from 1976-2022, including individuals born in the wild and those born in professional care. A review of necropsy and histopathology records was conducted to identify causes of morbidity and mortality, as well as associations among age, sex, and wild versus aquarium birth origin. Major causes of mortality included infectious diseases (n = 12), hemochromatosis (n = 10), undetermined (n = 10), and cardiovascular diseases (n = 8). Cause of mortality was significantly associated with sex (p = 0.015). Hemochromatosis and hepatic causes of mortality were identified exclusively in females. Infectious diseases were the most identified major cause of mortality and included septicemia (n = 7), toxoplasmosis (n = 3), leptospirosis (n = 1), and suppurative meningitis (n = 1). Of the septicemia cases, three were confirmed to be caused by Pasteurella sp. Hemochromatosis was the predominant cause of death in ten females from 8-25 years of age, with histopathology identifying hemochromatosis as a comorbidity in an additional male NFS. Hemosiderosis was a common finding in hepatic (n = 19), splenic (n = 15), lymph node (n = 6), ovarian (n = 3), bone marrow (n = 2), pulmonary (n = 1), and pancreatic (n = 1) tissues. In addition to hemosiderosis, the most common comorbidities affected the hepatobiliary (n = 36), urinary (n = 33), respiratory (n = 26), and lymphatic (n = 23) systems. While hemochromatosis has been previously reported in NFS, this is the first study to describe the prevalence in a professionally managed population. This study expands on the understanding of pathology in NFS to further improve medical management in professional care.