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Whales in San Francisco Bay

Roughly 30 gray whales have been spotted in the Bay this season, many more than is typical. Sadly, there have also been at least 14 deaths this year, which is more than in all of 2024. 

We are investigating to help determine the cause of these deaths. By gaining insights into what is causing these tragedies, we can better understand how to help prevent them.

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gray whale fluke
California sea lion Succulent

Association between Positive Canine Heartworm Testing in California Sea Lions and Nematode Infection

Association between Positive Canine Heartworm (Dirofilaria immitis) Antigen Results and Presence of Acanthocheilonema odendhali Microfilaria in California Sea Lions (Zalophus californianus)
  • Parasites
  • Diagnostics

Abstract

This study establishes a relationship between positive canine heartworm (Dirofilaria immitis) test results frequently observed in California sea lions (Zalophus californianus) and infection with the filarid nematode Acanthocheilonema odendhali. Four commercially available canine heartworm antigen tests were evaluated for cross-reaction with A. odendhali in California sea lions. Sera were tested from fifteen California sea lions with A. odendhali-associated microfilaremia, confirmed by blood smear, and with no evidence of D. immitis infection at necropsy. Ninety-five percent of tests were falsely positive for D. immitis. This study also determined that the prevalence of A. odendhali infection in stranded California sea lions from central California is approximately 23% by comparing the number of findings of mircofilaremia to the total number of California sea lions sampled at The Marine Mammal Center between 2005 and 2011, inclusive. Acanthocheilonema odenhali microfilaremia in California sea lions is likely to cross-react with canine heartworm antigen tests, and clinicians should interpret results with caution. 


Krucik, D.D.R., Van Bonn, W., Johnson, S.P. 2016. Association between positive canine heartworm (Dirofilaria immitis) antigen results and presence of Acanthocheilonema odendhali microfilaria in California sea lions (Zalophus californianus). Journal of Zoo and Wildlife Medicine. 47(1): 25-28.

parasites
diagnostics

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