The National Parks Board is calling for research proposals that aim to fortify Singapore against outbreaks of zoonotic diseases. -- ST PHOTOS: GAVIN FOO
SINGAPORE (The Straits Times/ANN): The bird, barely the size of a human palm, struggled in the mesh net hanging between two wooden poles on Pulau Ubin, the biodiversity haven located off Singapore’s eastern coast.
The snare had been installed at dawn on Dec 5, 2024 – at the height of the migratory season, when birds from the far north fly south to escape the winter chill.
It took just 45 minutes before the black-browed reed warbler was caught. A masked, bespectacled man approached the struggling ball of feathers, untangled it and slipped it into a cloth bag.
But Dr Gabriel Low is no poacher. The wildlife management researcher at the National Parks Board (NParks) is a “hunter” of a different kind, on the prowl for disease-causing pathogens in animal populations that could pose a risk to people in Singapore.
After samples are taken from the bird, Dr Low releases it back into the wild.
The notion of how human well-being is intimately intertwined with environmental health is gaining traction globally, with scientists and the World Health Organisation (WHO) urging governments to take greater consideration of the nexus between the two.
Singapore, too, is doing more on this front.
On Jan 3, NParks launched a call for research proposals that will look into how the nation can be fortified against future outbreaks of zoonotic diseases – which can spread from animals to humans.
The grant call, which will be open until March 28, is part of a $15 million biosurveillance research programme announced in 2024. Biosurveillance refers to efforts to monitor the environment for pathogens, or disease-causing agents, such as bacteria and viruses.
The grant call comes amid a slew of recent zoonotic disease outbreaks, including the ongoing mpox outbreak, which began in May 2022. The disease is spread by small mammals such as monkeys and squirrels, and spread rapidly in the African region, prompting the WHO to declare it a public health emergency of international concern on Aug 14, 2024.
The virus that caused the Covid-19 pandemic, which ravaged the globe from 2020 to 2023, has also been linked to bats, although research is ongoing to determine its origins.
Said Dr Chua Tze Hoong, NParks’ group director of veterinary health, of the focus of the grant call: “We want to look at diseases which affect mammalian wildlife, urban birds, as well as those carried by arthropods like ticks, and small animals like dogs and cats.”
In Singapore, these animal groups are known to harbour pathogens that could potentially spread to humans.
For example, leptospirosis – a virus spread mainly by rodents – was responsible for a wave of illness among pet dogs in Singapore in January 2024. The disease can also spread to people, and from 2012 to 2017, 289 cases of leptospirosis in humans were recorded in the Republic.
Mammals such as macaques are also the natural hosts of the simian B virus. This pathogen has sickened humans overseas, but no cases have been reported in Singapore.
A yellow-bellied prinia was among the birds caught during the National Parks Board’s Pulau Ubin biosurveillance exercise on Dec 5. -- ST PHOTO: GAVIN FOO
Healthy environment, healthy humans
The case for environmental protection has long been made by conservation groups and researchers to protect wildlife or tackle climate change.
But the links between a healthy environment and human health are also becoming stronger, in the wake of the recent outbreaks of diseases with origins in animal populations.
In December 2023, a new research programme focusing on climate, environment and health was launched at the NUS Saw Swee Hock School of Public Health.
The programme aims to deepen understanding of the health risks associated with changes in the climate and environment, such as how rising temperatures could lead to the spread of diseases like malaria or dengue.
It also studies how climate mitigation strategies may be executed with human health in mind. This includes how reforestation can be carried out without creating new habitats ripe for mosquitoes, which can act as vectors that transmit diseases from wildlife to humans.
Dr Kimberly Fornace, who leads the NUS programme, said that habitat disruptions impact the behaviour of wildlife populations, in terms of where they find food, how they move and how close they are to people.
“An animal that’s more stressed can also release more pathogens or become more infectious with certain diseases,” she added.
Climate change is one of the biggest health challenges of the next century, Dr Fornace said.
“It’s certainly something that’s very relevant for a tropical country like Singapore, as there are many kinds of climate-sensitive infectious diseases,” she added.
Singapore does not have many livestock farms or broad swathes of nature, but experts say the Republic has other vulnerabilities to zoonotic disease spread.
For example, as Singapore is a transit stopover and international hub for animal trade and products, many people and goods pass through its shores each day, increasing the risk of the transboundary spread of zoonotic diseases.
Dr Ng Lee Ching, group director of the National Environment Agency’s (NEA) Environmental Health Institute, said Singapore’s high population density and urban greenery could also increase contact between humans and wildlife.
Using the example of vector-borne diseases like dengue, Dr Ng said: “I always say that the mosquito is spoilt for choice in Singapore. It’s like a buffet.
“Less than a metre away, and there will be another 10 people surrounding you, so it’s very easy to infect people with just a single mosquito.”
The WHO has dubbed this approach of recognising the links between human health and that of animals and the environment as One Health.
The global health agency recommends that countries devise their own national One Health frameworks by creating an inter-agency government body, facilitating integration across organisations and furthering knowledge in One Health-related fields, among other things.
NParks officers setting up mist nets on Pulau Ubin to catch birds for biosurveillance before releasing them again. -- ST PHOTO: GAVIN FOO
Singapore’s One Health approach
Singapore established its One Health framework in 2012.
It comprises five agencies – NParks, Ministry of Health (MOH), NEA, the Singapore Food Agency and PUB, Singapore’s national water agency.
These agencies collaborate closely to monitor upstream biological risks in the environment by routinely taking samples from different animal populations – including poultry, wild birds and various insects – and analysing them for the presence of pathogens.
For example, to ensure Singapore remains free from highly pathogenic avian influenza, which is fuelling an ongoing global outbreak, NParks conducts checks on both wild birds and poultry.
Since 2020, a deadly strain of avian influenza, H5N1, has spread more widely than ever before – infecting cattle and humans in countries such as the US. In December 2024, the US reported its first severe case of bird flu in a human, a 65-year-old from Louisiana, who fell ill after being exposed to infected birds in backyard flocks.
During migratory bird season in Singapore, which is from August to April, NParks officers conduct sampling exercises similar to the one on Pulau Ubin every two weeks. For the rest of the year, sampling takes place once every two to three months.
Such checks on wild birds have been conducted since 2003, said NParks’ Dr Chua.
“Avian influenza is a global panzootic disease – which is the animal version of a pandemic. The virus may be carried by wild migratory birds. Not all of them die and succumb immediately, and can thus carry the virus over long distances,” said Dr Chua.
During wild bird surveillance, details of each bird caught – including its species and other biological data such as its weight, sex, age and wing length – are recorded. A metal ring with a unique code is then slipped around the right leg of each bird, to allow easy identification should it be recaptured.
A long cotton swab – akin to those in Covid-19 test kits – is used to take a sample of genetic material from the rear of the bird before it is released back into the wild. The samples are transported on ice to NParks’ Animal & Veterinary Service laboratory, where it undergoes testing for highly pathogenic avian influenza.
To date, bird flu has not been detected in wild birds tested by NParks.
As for imported poultry, NParks conducts checks before trucks carrying live chickens and ducks from Malaysia are allowed into Singapore.
At the checkpoints in Singapore, NParks officers first perform a visual scan of the poultry, checking for symptoms of disease in birds, and to see if any are dead.
Dr Chua said visible symptoms include a purple discolouration in birds’ wattles and combs, which are usually bright red. The discolouration happens because the virus attacks small blood vessels, causing blood to leak out of the capillaries.
If any sick or dead birds are found, swabs of genetic material from the rear of the bird will be put through a 20-minute rapid influenza test to check for the virus.
“If the initial test findings show a suspicion of disease, we will not allow entry of trucks into Singapore while we further investigate and send samples to the Centre for Animal & Veterinary Sciences for confirmatory testing,” said Dr Chua.
NParks officers also check documents to ensure the importer has secured the necessary permits and certificates, including from Malaysia’s Department of Veterinary Services.
Border biosurveillance has been conducted for more than 20 years, and no cases of bird flu have been detected at the border thus far, said Dr Chua. But since 2021, 18 trucks have failed the document check and were refused entry to Singapore.
Asked why Singapore’s One Health approach is important, NEA’s Dr Ng said: “Intervening downstream would mean only medical care – when you get sick, you go and treat it, but what we want is to move backwards to the source to solve the root of the problem.”
Dr Chua said that if any zoonotic disease of concern is detected by the agencies in their routine monitoring efforts, the relevant One Health agencies – including MOH – will be informed. The agencies would then work together to respond to any emerging zoonotic risks that may occur.
An NParks officer conducting a physical examination of live chickens and ducks at Tuas Checkpoint. --ST PHOTO: GAVIN FOO
The chikungunya intervention
From 2008 to 2009, Singapore grappled with an outbreak of a mosquito-borne disease called chikungunya.
The disease causes symptoms such as fever and joint pain, and was first reported in 1953 in Tanzania, a country in East Africa. During the 2008 to 2009 outbreak in Singapore, 1,033 cases were recorded.
Dr Ng said that despite repeated introductions of the chikungunya virus and its vectors, as well as low population immunity against the disease, chikungunya has not been able to cause explosive and lasting epidemics in Singapore.
“This attests to the robustness of our disease surveillance and aggressive vector control strategies in preventing severe chikungunya epidemics,” she said.
In Singapore, biosurveillance efforts against vector-borne diseases are conducted by NEA.
There are 182 species of mosquitoes in Singapore, although most people are aware of just one – Aedes aegypti, which spreads dengue. Other species of mosquitoes here include those from the genus Culex, which may transmit the West Nile virus and Japanese encephalitis virus – though both diseases are currently not endemic, or usually prevalent, here.
By tapping global public health networks and biosurveillance efforts, NEA said it is able to minimise the spread of vector-borne diseases in Singapore.
Dr Ng said: “Before chikungunya hit us, it was already happening elsewhere. We worked with these countries to understand the issue, and thus understood that it could be the Aedes albopictus mosquito that was transmitting it.”
When the virus hit Singapore, NEA could thus immediately sequence the genetic information of the disease-carrying mosquito and more precisely roll out targeted vector control.
As Aedes albopictus mainly inhabits outdoor habitats, while Aedes aegypti mainly colonises indoor spaces, when the former was thought to be the culprit in the disease, mosquito control strategies could be tailored towards external environments.
For instance, NEA may advise managers of premises with large outdoor spaces and greenery to keep a lookout for outdoor breeding habitats such as ground depressions, canvas sheets and tree holes. Chemical control measures, such as fogging, may also be intensified during an outbreak.
Singapore has a suite of measures to monitor mosquito populations.
Other than gravitraps, which are often seen at Housing Board block landings to catch the urban, day-biting Aedes aegypti, NEA also deploys traps in forested areas to keep tabs on other mosquito populations.
These include a trap called the night catcher, so called for its purpose of trapping night-biting mosquitoes, such as those of the Anopheles genus, which can spread malaria. The trap also catches other arthropods such as biting midges and sandflies.
“For sandflies, they are the main vector for leishmaniasis. And for biting midges, they are thought to transmit the Oropouche virus,” said Dr Wilson Tan, director of the NEA’s Vector Biology and Control Division, which is within its Environmental Health Institute.
The trap’s key feature is its 12 tubes, which rotate every hour to catch insects active at different hours of the night.
Senior research officer Ding Huicong said: “We can identify which insect species are the early biters, or which are found later, at maybe towards dawn.”
An NEA officer collecting samples from the night catcher mosquito trap at Jurong Lake Gardens.ST -- PHOTO: GAVIN FOO
Partnering with the community
Singapore’s One Health agencies also work closely with others in the community, including Mandai Wildlife Group, the operator of Singapore’s four wildlife parks, on biosurveillance efforts.
Home to more than 1,000 species of animals, Mandai employs a variety of strategies to ensure each one is healthy and disease-free.
To keep its birds safe from highly pathogenic avian influenza, Mandai taps NParks’ existing biosurveillance programme, sending in avian faecal samples monthly during the migratory season, and once every three months during the rest of the year.
Several design elements of Bird Paradise – which opened in 2023 – also help reduce the risk of disease transmission.
Each aviary is bordered by a layer of mesh. This restricts contact between the park’s birds and wild birds – which could be carrying disease.
Tucked away in each aviary are big cages where birds can be isolated if they display symptoms of disease. In the case of larger-scale disease outbreaks, Mandai also has its own isolation facility.
“One area we did design specifically for biosecurity is our quarantine building, which is completely separate from all of our parks,” said Dr Xie Shangzhe, Mandai’s vice-president of veterinary healthcare.
In partnership with NParks, Mandai is also exploring new ways of detecting disease in animals.
One way is to take environmental samples – where air and water in exhibits may be tested for the presence of pathogens. This could enable diseases to be detected even before animals start to display symptoms.
With the abundance of animal species within the Mandai group’s premises, Dr Xie and his team are keenly aware of the importance of biosurveillance. They perform checks and tests diligently, even for parasites such as nematodes and coccidia, throughout the year.
Dr Xie said: “Because we have almost 1,000 species in the park, basically any parasite is possible.
“Biosurveillance is the backbone of the preventive healthcare programme for all our animals.” - The Straits Times/ANN
