Abstract

Guadalupe fur seals (Arctocephalus townsendi; GFS) are endemic to the west coast of North America from Mexico to Washington State and were hunted to near extinction by the early 1900s. The population is now protected and has been increasing with a concomitant rise in strandings, though information on disease associated with these strandings is limited. Anemia presumed secondary to malnutrition, trauma, or chronic disease such as parasitism, is common and usually improves with appropriate treatment and supportive care. However, we report here seven cases of severe, progressive anemia of unknown origin in stranded GFS that were initially not responsive to routine medical care.

A total of 78 GFS pups and yearlings that stranded alive in California between 2015 and 2018 during an Unusual Mortality Event were treated at The Marine Mammal Center (Sausalito, CA, USA). All presented with malnutrition and the majority had mild anemia, but seven animals presented with and/or developed moderate to severe anemia during rehabilitation, with hematocrits as low as 7%. Most anemias were regenerative and three animals had concurrent leukopenia, suggesting potential bone marrow dyscrasia. Serum chemistry parameters, including iron, were highly variable among individuals. Diagnostic testing varied among cases but generally included fecal analysis, urinalysis, radiographs, ultrasound, and gastroscopy. Bone marrow aspirate and biopsy were performed in 3 cases. Serologic tests for exposure to Sarcocystis, Toxoplasma, Neospora, Leptospira, and PCR for Mycoplasma and Bartonella were negative. Treatment also varied among cases but generally included antibiotics (doxycycline and/or clindamycin), gastro-protectants, anthelmintics, steroids, iron, and nutritional care. Three animals eventually responded to treatment and the other four died or were euthanized due to progressive disease. Following cross-match, a blood transfusion consisting of packed red blood cells from a California sea lion (Zalophus californianus) donor and erythropoietin were administered to one animal with no evidence of transfusion reaction, although ultimately it did not survive. One animal had concurrent bronchopneumonia and hippocampal neuronal degeneration, and another had diplococci in the bone marrow suggestive of sepsis. Severe progressive anemia was considered the primary cause of death or euthanasia in two cases, though histopathological findings were inconclusive. The cause of the anemia was not identified in any of the released animals. As GFS may develop severe anemia that can be challenging to address with routine medical care, further studies to understand the cause of anemia in this species are warranted.

Acknowledgements

We are grateful to the staff and volunteers of The Marine Mammal Center for their dedicated patient care. Rehabilitation of the GFS were conducted under NMFS Permit 18786.

* Presenting author