The Los Angeles Zoo, Los Angeles, CA, USA; Division of Vector-Borne Infectious Diseases, National Center for Infectious Disease, Centers for Disease Control and Prevention, Fort Collins, CO, USA
During the late summer and early fall of 1999, an outbreak of viral encephalitis occurred in New York, resulting in fatal neurologic disease in humans and a variety of native and exotic birds, and horses. West Nile virus (WNV), a mosquito-borne flavivirus never before identified in the Western Hemisphere was shown to be the cause of disease.1 The virus has spread across the United States in the past 3 years, killing thousands of birds of many species, and is expected to cross the Rocky Mountains imminently reaching the home of the last 200 plus members of the endangered species, the California condor (Gymnogyps californianus).
The only commercially available vaccine is one manufactured and approved for horses. It is a killed vaccine in a lipid adjuvant (Metastim™) (West Nile-Innovator, Fort Dodge, Fort Dodge, IA USA) with variable results in some species of birds2,3 and of unknown efficacy in most species. The Centers for Disease Control and Prevention (CDC) has developed an experimental recombinant DNA plasmid vaccine in an aluminum phosphate adjuvant, that in experimental studies has shown promise in protecting two very sensitive crow species, fish crows (Corvus ossifragus) and American crows (Corvus brachyrhynchos) (Bunning et al., personal communication).
The CDC included the California condor in its evaluation of their experimental DNA plasmid vaccine. Eight Andean condors (Vultur gryphus) and 27 California condors residing at the Los Angeles Zoo were vaccinated twice, 21 days apart. Serum was collected at day 0, day 21, and at 3 months (or longer) post vaccine. There were no adverse reactions, and preliminary evaluations show good immune response to this vaccine, and further titer evaluation is pending. Vaccination of the rest of the population is in progress.
The candidate vaccine looks to be a promising one for future avian vaccination for WNV; however, it is currently for research only and not commercially available at this time.
The authors appreciate the assistance of Drs. Michael Bunning and Nick Komar from CDC, Dr. Branson Ritchie, Dr. Pat Redig, and the many other members of the West Nile Virus Working Group for the support that made this project happen, especially challenging with a very short timeline. Many thanks to Patti Bright and the American Bird Conservancy for their support, and to Michael Chambers of Aldevron who manufactured and donated the DNA for the vaccine for the condors. As always, without the extraordinary effort put forth by the Animal Health and Condor staff at the Los Angeles Zoo, this project would not have been possible. A final thanks to the leaders and members of the California Condor Recovery Team for backing this project without a moment of hesitation.
1. Steele, K.E., M.J. Linn, R.J. Schoepp, N. Komar, T.W. Geisbert, R.M. Manduca, P.P. Calle, B.L. Raphael, T.L. Clippinger, T. Larsen, J. Smith, R.S. Lanciotti, N.A. Panella, and T.S. McNamara. 2000. Pathology of fatal West Nile virus infections in native and exotic birds during the 1999 outbreak in New York City, New York. Vet. Pathol. 37:208–224.
2. Tully, T., M. Mitchell, J. Heatley, J. Nevarez, A. Roy, and B. Ritchie. 2002. Cockatiel (Nymphicus hollandicus) serologic response to equine West Nile virus vaccination. Proc. Assoc. Av. Vet. Conf. Pp. 79–81.
3. Okeson, D., S. Llizo, C. Miller, and A. Glaser. 200 I. Antibody response of four bird species after vaccination with a killed West Nile virus vaccine. Proc. Am. Assoc. Zoo. Vet. Addendum provided at conference.