California Sea Lions – Name The Zoonotic Disease They Carry

On a trip to San Fransisco and Monterrey, I spent time watching sea lions (Zalophus californianus) nap in the warm sun.  The females had given birth in June and then spent the summer nursing their pups.  The little ones grow rapidly on the rich milk.  The males keep a watchful eye over their territory.  They are much larger than the females and darker in color.  Males can weigh up to 1,000 pounds while females are closer to 200.

Unfortunately, California sea lions harbor a serious disease.  During an outbreak, many animals will die.  Name the disease and what organ(s) it affects.    

Diagnosis:  Leptospirosis

Leptospirosis is a deadly organism that affects creatures of all kinds, including humans.  The organisms causes liver and kidney malfunction.  According to scientists it “. . . is endemic in California Sea Lions but also causes periodic epidemics of acute disease.”  Researchers determined that sea lions who live by dog parks have a higher incidence of exposure.  It is also thought that seasonal migration plays a role in transmission.   

During an epidemic, sick animals haul out on beaches along the California coast line.  Since the disease is transmissible to humans (zoonotic), it is important to keep your distance.  Let wildlife personnel aid the distressed animals.  With fluid therapy, many will survive and return to a life at sea.  Below is a video clip from Monterey California.  The sea lions look like they don’t have a care in the world.  Enjoy!


Gullard, et al., “Molecular Markers , Mat and Modeling:  New Evidence for Leptospirosis in Californian Sea Lions Being Endemic with Periodic Epizootics, Defying the Host-Adapted Strain Paradigm for Leptospirosis.  IAAM 2009.

Norman, et al., “Risk factors for an outbreak of leptospirosis in California Sea Lions (Zalophus californianus) in California, 2004” J. Wildl Dis, October 2008; 44(4): 837-44.

Published by kristennelsondvm

Dr. Kristen Nelson grew up on a farm in Watertown, Minn., where she developed a deep love for animals of all kinds. She received a Doctor of Veterinary Medicine degree from the University of Minnesota, College of Veterinary Medicine. Kris then completed a small-animal internship at the prestigious Animal Medical Center in New York City. In addition to writing and speaking, she cares for small and exotic animals in Scottsdale, Az. Dr. Nelson is widely quoted in the media. Her credits include Ladies’ Home Journal, USA TODAY, the Los Angeles Times and numerous radio and television interviews. Dr. Nelson has written two books, Coated With Fur: A Vet’s Life and Coated With Fur: A Blind Cat’s Love. Kris and her husband Steve share their home with rescued cats, birds and a dog.