The critically endangered California Condor - whose population had declined to just 23 known survivors by the early 1980s due to the effects of DDT, lead poisoning, and a loss of habitat - has made a remarkable recovery with now roughly 500 birds in the wild or captivity.
This progress is due to primarily to conservation efforts by the US Fish & Wildlife Service, the National Park Service, and breeding programs at San Diego's Wild Animal Park and the Los Angeles Zoo. But the arrival of HPAI H5N1 to North America threatens these gains.
As scavenger birds, Condors feed almost exclusively on carrion, which increasingly runs the risk of being infected with HPAI H5 (see USDA Mammalian HPAI Infection List).
By early May the number of confirmed condor deaths had climbed to 21, and a few weeks later the USDA announced a pilot program to test an existing HPAI H5 poultry vaccine on vultures (a non-endangered species similar to Condors) in order to determine both its safety, and effectiveness against the currently circulating H5N1 virus.
Following reassuring results with vultures, in late July the FWS announced the start of the California Condor H5N1 Vaccination Trial. Since this H5N1 vaccine was initially designed to protect poultry (and against an older H5 strain), they needed to determine the optimum method (1 dose or 2) of administering this vaccine, and how much protection it provides.
Blood samples would be collected from a small number of captive birds at 21-days and 42-days post vaccination to evaluate the immune response from two different vaccination approaches.
California Condor HPAI Response Update - October 16, 2023Early vaccine trial results available; birds from L.A. Zoo, San Diego Zoo Wildlife Alliance and Oregon Zoo participated in trialOct 16, 2023
The U.S. Fish and Wildlife Service’s Incident Command Team, in collaboration with partner agencies, continues to develop and implement conservation strategies to help California condors considering Highly Pathogenic Avian Influenza (HPAI).
Incident Update
California Condor Vaccination Trial
Final analysis for the samples from Group 1 for condors are complete. USDA conducted hemagglutination inhibition tests on serum samples collected 42 days after the vaccination. The samples were evaluated for antibody titers that are commonly used as surrogate markers against influenza and other pathogens.
Group 1 received a vaccination of 0.5ml on two occasions (initial injection and booster). Results show that 60% of the condors had titers that are expected to provide partial protection against mortality, while 10% of those birds had titers expected to provide protection against mortality.
Group 2 received a single 1 ml dose vaccine. Results pending.
10 condors completed vaccine administration.
10 condors have completed the 42-day trial period.
Group 3 includes control birds. They will not receive vaccines, but blood samples will be collected.
Additional hemagglutination inhibition tests are being conducted to provide a better understanding on the duration the birds may be protected and to what extend from the currently circulating strain of HPAI.
Field Operations
The Service determined that based on the results from Group 1, release birds for this fall and winter will be vaccinated with the Group 1 regimen (two 0.5ml doses) prior to release. The vaccine should provide some level of protection from mortality if the birds are exposed to the virus, and likely decrease the degree to which an individual becomes ill.
This will result in 14 additional birds being vaccinated, leading to a total of 26 vaccinated release birds (including those in the trial). Release of individuals will continue to be dependent on the individual’s behavior and conditions at the local release site.
The Service is working with USDA, U.S. Geological Survey, State Veterinarians, and recovery partners to develop site-specific vaccine plans for each of the zoological institutions that care for condors and the release sites so vaccines can be implemented prior to release.
Prior to expanding the use of the vaccine in captive and free-flying condors in future years, the Service will (1) complete the current vaccine trial (2) evaluate changes in the level of antibodies in vaccinated condors over time and (3) evaluate condors for antibody titers in Arizona/Utah population that may have been previously exposed to HPAI and survived.
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