A serious avian influenza H5N1 outbreak at the Dählhölzli Zoo prompted veterinarian Stefan Hoby to collaborate with the Federal Institute of Virology and Immunology to develop a vaccine for zoo birds. Trials began in August 2023, showing promising results. Although the vaccine is safe and effective, challenges remain in commercial production and distribution. The need for a manufacturing partner is urgent, especially with competition from a newly available vaccine in France.
A Critical Challenge for Zoo Veterinarians
Two years back, a distressing incident unfolded at the Dählhölzli Zoo in Bern, sending chills down the spines of zoo veterinarians. The tragic discovery of two wild gray herons found lifeless marked the onset of a serious threat: the highly pathogenic avian influenza H5N1. Not long after, a curly-headed pelican from the zoo also succumbed to the virus.
Fortunately, the situation did not escalate, and the virus remained contained, sparing the other zoo birds from a catastrophic fate. When outbreaks occur, it often leads to the culling of entire animal populations, as witnessed in January at the Stralsund Zoo, where over a hundred birds were euthanized.
Innovative Solutions for Bird Protection
In response to the looming threat, veterinarian Stefan Hoby took swift action by collaborating with the Federal Institute of Virology and Immunology (IVI) to devise an innovative avian influenza vaccine specifically for zoo birds. The initiative gained momentum rapidly, and researchers at the IVI were able to develop an experimental vaccine targeting the H5N1 strains currently prevalent in Europe and the USA.
Since August 2023, this groundbreaking vaccine has been undergoing trials at both the Dählhölzli Zoo and the Basel Zoo, involving 317 birds across 24 species. Promising results were unveiled recently, showcasing the effectiveness of this tailored vaccine.
The rapid development of the vaccine stemmed from a decade of foundational research at the IVI. The vaccine utilizes a harmless carrier virus, into which an antigen from the avian influenza virus is integrated. This approach allows the vaccine to be administered intramuscularly to the zoo birds, leading to the production of antibodies without posing any health risks to the animals. A booster shot was administered five weeks later to enhance the immune response.
Since the alarming incident two years ago, there have been no further reports of avian influenza among birds near the Bern Zoo. Although the exact level of immunity in vaccinated birds remains uncertain, blood tests confirm that all vaccinated individuals developed adequate protection against the disease.
“This vaccine is entirely safe, with no observed side effects,” states Christian Wenker, a veterinarian from the Basel Zoo. However, the vaccination process itself presented challenges. Catching and vaccinating zoo birds proved to be quite the task. “To vaccinate a flamingo, you must hold it like a rock guitar,” Wenker explains, highlighting the lengths animal keepers had to go, which sometimes involved wading into the water in swim trunks. Nevertheless, these efforts are vital, as vaccination not only safeguards against the virus but also reduces the need for confinement or, in dire situations, the culling of cherished zoo animals.
Despite the encouraging outcomes, the future of the vaccine remains in limbo. Zoo veterinarians are eager to conduct additional vaccinations in the fall, but there is a pressing need for a manufacturer capable of producing the vaccine commercially and obtaining the necessary licenses.
Currently, IVI researchers are seeking investors to transform this experimental vaccine into a marketable product. However, the Swiss market presents its own challenges, as there are no existing manufacturers, and the veterinary sector typically offers slim profit margins.
Adding to the complexity of fundraising efforts, a new H5N1 vaccine has recently entered the market in France, already in use for large-scale duck farming operations. This development raises questions about the effectiveness of the French vaccine, as no published data is available yet. Nevertheless, the IVI team remains hopeful, with virologist Gert Zimmer emphasizing the need for comparative testing between the two vaccines.
Ultimately, it remains unclear which vaccine will provide superior long-term protection, given the varied lifespans of different bird species. While ducks typically live only three months and laying hens over a year, flamingos can thrive for up to 80 years. Fortunately, birds at the Bern Zoo still exhibit sufficient antibodies a year after vaccination, suggesting a potential market gap for the IVI vaccine. Gert Zimmer is optimistic about the unique advantages of their vaccine but acknowledges the necessity of finding a partner company that shares their vision.