SINGAPORE: Last year, when an exotic disease reached Singapore’s shores, a chain of testing, investigation and contact tracing was triggered to contain it.
It's not COVID-19, but rabbit haemorrhagic disease or RHD - a deadly disease for bunnies that was detected in Singapore for the first time last year.
In September 2020, a notice was sent out to all rabbit owners to minimise contact between their pets and other rabbits as the illness is highly contagious.
Back then, eight out of 11 rabbits died within two days of being sent to the vet. Two rabbits recovered after “prolonged hospitalisation” and one was found not to have the disease, according to a research paper published in Transboundary and Emerging Diseases on Apr 23.
For infectious diseases affecting animals, the National Parks Board’s (NParks) Animal and Plant Health Centre plays a key role in examining the issue at hand and formulating solutions.
Tucked away in Lim Chu Kang, the centre has a team of experts including veterinarians, microbiologists and laboratory technologists.
During a visit to the centre on Monday (Jul 12), Dr Kelvin Ho, senior vet at the Animal & Veterinary Service, said that their job was like being a “disease detective”.
He told reporters that when the first RHD cases were reported, the centre reached out to vets, particularly those with more rabbit patients.
The vets also sent samples from the cases they had seen to the laboratories at the centre for testing - liver tissue samples from infected rabbits showed signs of massive bleeding. The lab then used Polymerase Chain Reaction (PCR) tests to confirm that it was RHD.
Dr Ho said they also reached out to a tight-knit and active community of rabbit owners who sometimes held rabbit parties - something which caused concerns as such events would help the disease to spread. However, COVID-19 restrictions meant that there were no recent gatherings then.
“Part of the disease investigation is contact tracing. So we identified cases, we got the history from the vet: Where did they go? Did they go to any party?” he said.
The vets and scientists tried to search for the source of the infection but to no avail. They did however help procure a vaccine, which was not previously available here as the disease had never been found in Singapore.
Although RHD only affects rabbits, the centre is also on the lookout for zoonotic diseases - those which can spread from animals to humans - such as bird flu, rabies and coronaviruses.
This includes monitoring the birds and bat population here as well as other wildlife that live in close proximity with humans, such as palm civets.
This could involve collecting bat guano, or droppings, and sampling roadkills and injured bats brought to them, said Dr Benjamin Lee, director of Wildlife Management Research at NParks.
Dr Lee said that bats are a very diverse mammal group and about a fifth of the world's mammals or about 1,400 species are bats. This diversity means that they harbour a large number of viruses.
“The wildlife will not necessarily fall sick even if they have the viruses,” said Dr Lee. “Bats are a very good example because they have this really unique and special immune system that has evolved over the years ... to combat the viruses.”
So far, nothing of concern has been found. But by regularly surveying the bats since 2011, particularly those living near urban areas, the team is then able to find out what viruses are present in the healthy population of bats, he said.
While it doesn’t happen in Singapore, people harvesting wildlife and eating them can lead to diseases skipping from animals to humans. By having a better understanding of what is present in the environment, people would understand “how these connections (in nature) work, and then not to disrupt any of these connections for optimal health outcomes”, said Dr Lee.
DEADLY OUTBREAK IN HORSES
Dr Charlene Judith Fernandez, director of the Centre for Animal & Vet Sciences, said that one of the main tasks of the Animal & Plant Health Centre is to prevent the “incursion of exotic disease”.
As Singapore is largely urban with few farms, the centre’s role may not have a high profile - unlike in countries with large agricultural sectors. But Dr Fernandez emphasised that it is important to protect the animal populations in Singapore because they are small.
An example is African Horse Disease, described as one of the most feared infectious diseases for horses, which surfaced in Thailand last year. More than 90 per cent of horses die if they contract the disease.
In various provinces in Thailand, horses were dying suddenly and African Horse Disease was not initially suspected as it was not endemic. It was a “shock” to find that it had come to Southeast Asia, said Dr Fernandez.
If let loose among Singapore’s horses, of which there are fewer than 2,000, the consequences would be “disastrous”, said Dr Fernandez.
“If we have an incursion of an exotic disease that is significant, especially if it's a significant public health issue, everybody's at risk, and we don't just stop at our own borders, we have partnerships with our regional neighbours,” she said.
“We cannot wait until something comes into Singapore, we have to make sure that we have our eyes on the horizon. If something happens in the region, generally it would be a matter of time before it hits us.”
The centre has close ties with Singapore’s ASEAN neighbours and also works closely with Australia and the United Kingdom, she added.
“FIRST AND LAST LINE OF DEFENCE”
Because of the centre’s close ties with neighbouring countries’ laboratories, they had an early heads-up about the horse disease, said Ms Wendy Sng, deputy director at AVS’ Veterinary Health Management.
Ms Sng said that this was a case in which the centre had set up systems to deal with potential threats before they appear.
For instance, the disease is spread by biting midges which they had already identified as an area of concern for surveillance. Even before the African Horse Disease alert, they had worked with the National Environment Agency to modify mosquito traps for midges, which were smaller in size.
As a precaution, they deployed these at the Turf Club, which has the largest herd of horses in Singapore.
The centre also helped identify the specific serotype of the African Horse Disease using a PCR test, which helped to narrow down the vaccine for the horses.
The lab had already acquired technology to quickly sequence the genome without having to culture the original sample - thus saving weeks of time.
This all happened in about a weeks’ time after receiving the sample from Thailand, said Dr Huangfu Taoqi, deputy director at the Centre for Animal and Veterinary Sciences.
While the disease was not found in Singapore, it is now on the centre’s radar.
“We're almost like the first and the last line of defence for animal health ... there's nobody else that's going to do that in Singapore,” said Dr Charlene Judith Fernandez (Director of Centre for Animal & Vet Sciences).
“It doesn't mean that we don't have collaborators or partners whom we work with, but the responsibilities lie with us.”