Abstract
Leptospirosis is a widespread bacterial zoonosis of global importance and affects most mammalian species.6 Evidence of Leptospira infection or exposure has been reported in a number of pinnipeds that inhabit the eastern Pacific Ocean, including California sea lions (CSL; Zalophus californianus), northern fur seals (Callorhinus ursinus), northern elephant seals (NES; Mirounga angustirostris), Pacific harbor seals (Phoca vitulina), and Steller sea lions (Eumetopias jubatus).2-5,8,9 Seasonal epizootics of varying magnitude occur in CSLs, and serologic, epidemiologic and genetic data suggest that Leptospira interrogans serovar Pomona is enzootic.1,7 Leptospirosis has been documented in stranded and rehabilitating NES, is less commonly reported, and has been associated with leptospirosis outbreaks in CSL, suggesting CSL to ES transmission. In spring 2022, prior to a major CSL leptospirosis outbreak, seven weaned NES pups stranded in California, Oregon, and Washington with evidence of acute leptospirosis. Six NES died or were euthanized within three days of stranding and the seventh was euthanized after 25 days. These NES presented with malnutrition, lethargy, and dehydration; showed marked azotemia and hyperphosphatemia on serum chemistry or aqueous humor analysis; and had tubulointerstitial nephritis and tubular necrosis consistent with leptospirosis on histopathology. Five of the seven had serum analyzed by microscopic agglutination testing (MAT), and all had high (>1:3200) anti-Leptospira interrogans serovar Pomona antibody titers. Two ES without MAT results were PCR positive for Leptospira interrogans. The fact that these ES leptospirosis cases occurred prior to the CSL outbreak brings into question the role that ES may play in Leptospira transmission dynamics.
Acknowledgements
The authors thank the staff and volunteers associated with the NOAA West Coast Region Marine Mammal Stranding Network for their efforts in pinniped response, rehabilitation, and conservation.
*Presenting author
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