Comparison of West Nile Virus Titers in Four Species of Penguins Vaccinated with a DNA Plasmid Vaccine or a Killed Whole Virus Vaccine
West Nile virus (WNV) has caused morbidity and mortality in numerous captive and free ranging avian species worldwide, including African penguins (Spheniscus demersus) and Humboldt penguins (Spheniscus humboldti) (Glaser, personal communication). Many zoological facilities have initiated WNV vaccination protocols to at risk or endangered avian species. Knowledge regarding immunologic response by penguins to WNV vaccines is limited. One study has shown variation in humoral response to an inactivated vaccine between two penguin species.3 DNA vaccines have shown promising results in stimulating both cellular1 and humoral response4 to WNV. In avian species, however, humoral responses have varied between species.4,5 In this study, humoral immune responses to two WNV vaccines were compared within and between four species of penguins housed indoors with minimal potential for natural exposure induced titers. Pre- and post-vaccination WNV titers were determined and compared in Humboldt, Magellanic (Spheniscus magellanicus), Gentoo (Pygoscelis papua), and Rockhopper (Eudyptes chrysocome) penguins immediately prior to and for set intervals up to 1 year following vaccination with a commercially available equine killed virus vaccine (West Nile-Innovator, Fort Dodge Animal Health, Fort Dodge, IA, USA) or a newly developed DNA plasmid vaccine (experimental, not currently available). Additionally, methods were followed2 to isolate and cryopreserve lymphocytes from penguins at each sampling interval to allow for future cellular immune testing. Preliminary results demonstrated difference in humoral response to the two vaccines with the inactivated vaccine appearing to induce stronger and/or longer lasting antibody titers in more birds than the DNA vaccine. Interspecies differences were also observed.
We thank the Chicago Board of Trade Endangered Species Fund, the Penguin Taxon Advisory Group, and Brookfield Zoo for their funding of this project. We thank the animal husbandry and veterinary services departments at Brookfield Zoo, Shedd Aquarium, and John Ball Zoo for their many hours of assistance. We also thank Dr. Tom Meehan, Dr. Patty McGill, Dr. Branson Ritchie, Dr. Amy Glaser, Dr. Kathryn Gamble, Gail Nachel, and Edward Davis.
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