Abstract

Encephalitis and associated morbidity from West Nile virus (WNV) has been confirmed in several species of marine mammals including sea otters (Enhydra lutris).^1-4 A killed WNV vaccine (Fort Dodge West Nile Innovator©) was evaluated in 9 captive sea otters to determine vaccine safety and antibody response. The vaccine was administered intramuscularly at day 0 and again at day 30. Animals were monitored daily for adverse effects and titers measured at days 0, 30, and 90 post-vaccination. All samples were screened with a modification of Ebel's wild bird WNV enzyme immunoassay (EIA) using anti-dog IgG, as well as a duplicate series of plaque reduction serum neutralization tests (PRNT) performed at the USGS National Wildlife Health Center and the Cornell Animal Health Diagnostic Center.^5,6 None of the animals included in the study had measurable titers at day 0. Vaccination resulted in neutralizing antibody production in 5 of the 9 vaccinated animals (55%) at day 30 and 90. The level of neutralizing antibodies produced was between 1:20 and 1:40 with a plaque reduction of 80%. Other types of vaccines such as a recombinant canary pox-vectored vaccine may produce higher levels of neutralizing antibodies; however, reactions to live and modified live vaccines have been noted in sea otters. No adverse reactions to vaccination were noted. Protective efficacy of the WNV vaccination in sea otters was not evaluated. Vaccination of sea otters against WNV may be warranted in high risk areas or in rehabilitation situations, such as during oil spill response situations, combined with management practices aimed at limiting exposures to potential vectors.^7,8

Acknowledgements

The Seattle Aquarium would like to thank the Monterey Bay Aquarium and the Minnesota Zoo for their generous support of this study. We would like to thank Dr. Hendrink Nollens and Dr. David Jessup for their assistance with project design.

* Presenting author

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