With a wingspan of 9.5 feet, California condors are the largest birds in North America. They also are one of the most critically endangered. Population numbers declined throughout the 19th and 20th centuries, reaching a nadir of just 22 birds remaining in the wild in 1982. Myriad factors, including hunting, lead poisoning, habitat loss and the use of DDT contributed to this decline. Now, these magnificent birds now face a new threat—highly pathogenic avian influenza viruses. To combat this current hazard, conservation biologists are turning to a strategy that we rely on to protect ourselves from infectious agents, vaccines.
Although the California condor remains endangered, various strategies have bolstered its numbers since 1982. At that time, all wild condors were trapped and placed in captive breeding programs. Then, in the mid-1990s, conservation biologists began releasing captive-bred condors back into the wild. Today, roughly 350 birds exist in the wild, in five different flocks. Another 200 birds exist in captivity.
Lead poisoning and habitat loss remain a threat to these birds. Now, avian influenza virus also poses a threat. Since the early 2000s, highly pathogenic avian influenza viruses have spread throughout the world. Although these viruses have been isolated from numerous bird species, the effects on poultry have been especially dramatic. These viruses can spread rapidly within a flock of chickens, with a high mortality rate. To limit the spread, poultry farmers often cull the entire flock if an infected animal is detected. Since early 2022, over 50 million birds have been culled in the United States alone.
Wild birds, including the California condor, also have been affected. According to the U. S. Fish & Wildlife Service, 21 condors in Arizona, or about 20% of that flock, died between March and May 2023. Avian influenza virus was detected in 17 of them. Most likely, the virus was transmitted to a condor from another bird. Luckily, the virus has not been detected in condors present in Utah, California or Baja, Mexico and no additional positive birds have been detected in Arizona since May.
To protect condors from this new threat, researchers hope that vaccines may be the answer. In 2016, the Animal and Plant Health Inspection Service, a part of the United States Department of Agriculture, approved for use in animals an influenza virus vaccine developed by Zoetis. However, the safety and efficacy of this vaccine in California condors had not been examined.
To investigate the potential usefulness of this vaccine in condors, an initial trial recently began at the Carolina Raptor Center, a raptor rehabilitation and education center in North Carolina. According to Erin Katzner, president and CEO of CRC, 28 black vultures are involved in the study, which is being conducted in collaboration with several federal, nonprofit and private entities. Ms. Katzner explained that vultures were selected for this trial for two primary reasons. First, they are closely related to condors, making them good surrogates. Second, there is a robust population of these birds in the local area, making them easily accessible.
Twenty vultures have been vaccinated. Ten received a single dose of the vaccine and 10 received two doses, spaced 21 days apart. The remaining eight animals were not vaccinated, thus serving as controls. None of the animals showed any measurable vaccination-associated side effects. Currently, blood drawn from all animals is being analyzed to determine its HPAI antibody titer, or the level of antibodies in the blood that react with highly pathogenic avian influenza viruses. Hopefully, the vaccinated animals will exhibit elevated antibody titers, thus indicating that they may have developed some resistance to the virus. If researchers confirm that the vaccine is safe in vultures and it leads to the production of HPAI-specific antibodies, then researchers will begin to vaccinate condors in breeding colonies and later, wild condors. Thus, this vaccination program could provide the endangered condors with some protection against the latest scourge affecting it.
Why does this matter?
Protecting California condors just so future generations of humans can see them soaring through the sky may be a reasonable answer to this question. But the CRC’s Erin Katzner argues that the real answer is more profound. According to her, saving the California condor from extinction shows that when people work together, we can save a species. For her, the California condor serves as a beacon of hope. While humans often cause the problems that negatively impact other species, we also can develop solutions to those problems. Moreover, Katzner notes that challenges faced by raptors like the California condor often reflect challenges that we also face, whether those challenges involve pollution, habitat loss or infectious diseases like HPAI. As she remarked, “When raptors thrive, we thrive. If we save raptors, we save ourselves.”
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