Abstract

During the spring and summer of 2010, 12 stranded juvenile California sea lions (Zalophus californianus) presented to The Marine Mammal Center (TMMC) in Sausalito, CA, USA in poor body condition and died or were euthanized due to poor prognoses. On postmortem examination, all sea lions had extensive chronic granulomatous inflammation throughout the thoracic and abdominal cavities, affecting visceral adipose tissues, pleural and peritoneal surfaces, and various parenchymal organs. Inflammation was characterized by extensive accumulations of macrophages, and fewer lymphocytes and plasma cells, amongst both immature and mature fibrous connective tissue with regions of fat necrosis, perivascular inflammation and vasculitis. Although histologic lesions were highly suggestive of an infectious etiology, no causative agents were detected using routine, special and immunohistochemical stains, bacterial and fungal cultures, electron microscopy, and molecular diagnostics including targeted and universal PCR assays, and viral metagenomics. Based on these negative findings and substantial steatitis noted in all cases, non-infectious inflammatory conditions were considered, specifically nutritional pansteatitis secondary to oxidative stress. Vitamin E levels in liver and serum did not corroborate deficiency as seen in other animals with nutritional pansteatitis. The cause of this “skinny fat syndrome” has not been confirmed though an infectious etiology is still considered most likely. There have been no other recognized cases of this syndrome in stranded sea lions before or since this cluster, despite recent unprecedented strandings of malnourished juvenile California sea lions.

Acknowledgements

We thank Drs. Vanessa Fravel, William Van Bonn, and Denise Greig; Lauren Rust, Jennifer Soper, Christine Fontaine, Barbie Halaska, and Carlos Rodriguez, and the staff and volunteers of The Marine Mammal Center for their support. Thanks to Renee Walker and staff of University of Illinois Histology Laboratory for technical assistance. We thank Lois Hetmore (U of I) and Dr. Vincent Meador for their expertise in electron microscopy. Finally, the authors thank Dr. Eric Delwart of UCSF for his continued work on viral sequencing and discovery.

* Presenting author

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