Zoo vaccination efforts don’t target every animal, but focus on rare, disease-prone species: Experts

SINGAPORE - Animal vaccines have for centuries been used in farms to prevent diseases from spreading among livestock, but this tool is increasingly being used for another purpose: to safeguard endangered species from succumbing to infectious diseases.

This comes as climate change and globalisation accelerates the spread of pathogens around the world, with highly pathogenic avian influenza (HPAI) detected even among the penguins and seabirds on the uninhabited Antarctic region.

On Nov 19, Singapore announced that it will be conducting a pilot to vaccinate against HPAI potentially

up to 10 species of birds

across the wildlife parks managed by the Mandai Wildlife Reserve, starting from 2026.

The pilot programme is a joint effort undertaken by the National Parks Board (NParks), Mandai Wildlife Group, Temasek-backed French company Ceva Animal Health, and endowment fund Ceva Wildlife Research Fund.

But the strategies behind vaccinating wildlife in zoos would be different from immunising farm animals, experts told The Straits Times following the announcement.

A poultry farm, for instance, would vaccinate all of its chickens to prevent economic losses and food shortage from an outbreak.

However, vaccination programmes in zoos do not need to administer shots to every individual bird because not all avians in a zoo face the same level of risk, Dr Pierre-Marie Borne, director of the Ceva Wildlife Research Fund, told The Straits Times.

Some species reside in outdoor enclosures, and can come into contact with wild birds, so their risk of getting infected is higher.

He added: “This doesn’t stop the virus from entering the zoo, but it significantly reduces its impact, especially for rare or endangered species.”

Such a vaccination strategy has already been tried out in other zoological institutions. In Belgium’s Pairi Daiza zoo, for example, the vaccines have been given to the African penguins, great white pelican and Australian pelican.

Mandai Wildlife Group added that within the collection of species held in zoos, different species have varying susceptibilities to the virus.

“For instance, cranes have historically shown natural resistance to traditional HPAI strains. However, as the virus continues to evolve, newer strains have begun to affect species previously considered resistant,” it said. 

Mandai Wildlife Group manages five zoological parks, including Singapore Zoo, Bird Paradise and Rainforest Wild Asia.

Birds of prey and threatened species in the wildlife parks – such as the brahminy kite and critically endangered white-backed vulture – could be among the feathered animals that will receive the mRNA vaccine.

Mandai’s spokesperson said the objective of the upcoming pilot will enable researchers to assess how the vaccination can be applied across a broader range of bird species, and to understand its effectiveness in enhancing protection against HPAI.

Blood will be taken from vaccinated birds to check for antibodies and the strength of the immune response.

The vaccine’s safety will be closely monitored by observing any potential side effects or adverse reactions, said NParks. These will help determine the success of the pilot and whether it can be scaled up.

Mandai Wildlife Group has an existing bird flu vaccine programme. 

But the partnership with Ceva is to trial the company’s latest generation mRNA vaccine – which targets the currently circulating H5 strain of avian influenza – and also extend its use to a wider range of bird species.

The current global outbreak, which had a resurgence in 2022, has been unprecedented in its spread, wiping out poultry farms from Europe to Brazil, and even infecting more than 50 species of mammals including the elephant seal and humans.

Symptoms of bird flu in humans include eye redness, respiratory symptoms and fever, and even pneumonia and brain inflammation if cases worsen. On Nov 22, a Washington state resident died from the rare H5N5 strain of the virus, and the patient had a backyard flock of domestic poultry.

Public health experts have said that the global spread of zoonotic diseases - illnesses that can spread from animals to human, such as HPAI - has reinforced the importance of taking a One Health approach.

Such an approach recognises the close interconnection between human, animal, and environmental health.

In certain cases, the vaccination of wildlife, including endangered ones or those in closer proximity to humans, could be one way to safeguard this.

Ceva’s mRNA vaccine – similar to the technology behind some Covid-19 vaccines – sends cells a genetic instruction that induces an immune response. A substance is produced, prompting the immune system to create protective antibodies. These then prevent the virus from infecting the birds.

In comparison, the vaccines commonly used in poultry farms are inactivated vaccines, typically given to newborn chicks, as they must be administered before any risk of infection.

But the mRNA vaccine can be given to avians of any age. The vaccine can also be updated far more easily to match new circulating strains, unlike inactivated ones, said Dr Borne.

Apart from carrying out vaccination drives in zoos, Ceva Wildlife Research Fund has supported a French team that travelled as far as the Crozet Archipelago in the sub-Antarctic to immunise a population of king penguins.

“(The virus) is a full disaster in Antarctica. It destroyed many animals, penguins, sea lions. When a pathogen like this arrives on very naive species – not having even been touched by the flu – they die,” said Ceva’s chief executive Marc Prikazsky.

While it may not be practical to vaccinate all wild birds, like those in Singapore, it could be possible to vaccinate birds abroad that are not afraid of being approached and can be monitored post-inoculation, said Dr Borne.

Those include specific island-bound populations like the penguins, or albatrosses that return to the same nesting site every year.

Singapore investment company Temasek has been investing in Ceva since 2014.

Asked the reason for this, the firm’s managing director and head of agri-food Anuj Maheshwari, said: “Temasek decided to invest in Ceva because the investment company believes that animal health is fundamental to resilient food systems and public health.

“Ceva’s commitment to science-led innovation stood out as essential for addressing global challenges in food security and disease prevention,” he added.

Dr Prikazsky said Ceva is currently in discussions with the Singapore authorities about introducing a new rabies vaccination programme here, where edible vaccines are hidden inside bait.