Sabah's wild pigs are being stalked by a killer virus


  • Living
  • Tuesday, 23 Mar 2021

Scientists collecting tissue samples from a dead wild pig in Sabah. - Sabah Agriculture and Fisheries Ministry

Before Covid-19 restrictions put an end to the stream of visitors to Sabah, dozens of tour buses and vans used to stop along the long, winding two-lane highway between Tamparuli and Kundasang. Most of the tourists – usually Chinese nationals – were either on their way to or from Mount Kinabalu and would stop for another of the state’s attractions: sinalau bakas, or smoked wild boar.

Amidst smoke rising from barbecue pits, they would feast on the smoked wild boar meat that sold for between RM20 and RM26 a kilo. However, these days, most of the stalls along the road – known among tourists as the sinalau bakas highway – are shuttered, as are those in tamu markets as well as high-end shoplots. But it isn’t the pandemic that closed down most of these shops but another dreaded disease: African swine fever (ASF).

ASF ravaged herds of domestic pigs in China in mid-2018 and still occasionally crops up there, most recently in Sichuan. Now the virus has made an appearance in Sabah. Unlike the coronavirus, ASF is not at all dangerous to humans but it is deadly to pigs, domestic or wild – it has a staggering mortality rate of almost 100%.

A bearded pig in the wild captured by a camera trap. Could we lose these hardworking 'forest gardeners’ to African swine fever? - FilepicA bearded pig in the wild captured by a camera trap. Could we lose these hardworking 'forest gardeners’ to African swine fever? - FilepicEconomic losses

Malaysia had hitherto been free of the virus that is originally endemic to sub-Saharan Africa before it was first officially detected in Sabah early last month. This is despite the highly contagious haemorrhagic disease appearing in livestock in Indonesia, the Philippines and Vietnam.

Quick take on African swine feverQuick take on African swine feverWith infected pigs almost certain to die, sometimes within a week of contamination, the fever’s economic impact is devastating. At the peak of the epidemic in late 2018 and 2019, over 100 million pigs in China either died or had to be culled.

Already Sabah’s population of wild pigs, the Bornean bearded pig (Sus barbatus) and the common wild boar (Sus scrofa), are threatened, with pictures of dead animals turning up on social media in late January.

Scientists had warned of this possibility: A paper entitled “African Swine Fever threatens South-East Asia’s 11 endemic wild pig species” was published by members of the Society of Conservation Biology in December 2020.

In fact, a team of scientists in Glasgow University has even posited that the ASF outbreak in China could have led people there to seek out alternative sources of meat, triggering the zoonotic Covid-19 to spill over into humans. The timeline makes it an interesting (albeit yet to be peer reviewed) theory.

Dying by the dozens

A file photo of a vendor preparing sinalau bakas, or smoked wild boar, at a roadside stall in Sabah. Such stalls have been shuttered in March 2021 as Sabah’s pigs, both domesticated and wild, are being threatened by African swine fever. - 123rf.comA file photo of a vendor preparing sinalau bakas, or smoked wild boar, at a roadside stall in Sabah. Such stalls have been shuttered in March 2021 as Sabah’s pigs, both domesticated and wild, are being threatened by African swine fever. - 123rf.comOn March 10, Sabah Wildlife Department director Augustine Tuuga said that the department had received reports of ASF deaths in the state's wild pig population in late December 2020. This is even before the pictures of dozens of dead wild boar in Kinabatangan in eastern Sabah and in the Sugud and Paitan areas in the north-east went viral.

“Until now, we have detected at least 100 of these deaths in several areas in north-eastern Sabah, Kinabatangan, Tawau, the central region and most recently in Tabin, ” he said in a response to a question during a March 10 panel discussion hosted by WWF-Malaysia on Facebook Live.

Tabin is also the location of the Tabin Wildlife Reserve, a 122,539ha home to indigenous species, including wild pigs.

The webinar, themed Protecting Ecosystem: Why is Protecting Our Forests and Our Oceans So Important for Our Wellbeing, was organised in collaboration with the United States Embassy.

Tuuga’s comment confirms what Deputy Chief Minister and state Agriculture and Fisheries Minister Datuk Dr Jeffrey Kitingan announced on March 17, 2021: the disease is spreading ("Pig culling in Sabah to continue until spread of ASF is stopped", The Star).

On Feb 9, Kitingan told The Star that initial results of tests of tissue samples from dead wild boar on the east coast showed that it was not ASF, only for the virus to show up in samples from dead animals in Pitas on Feb 21.

ASF has so far infected domestic pigs in Kota Marudu and Pitas and wild boar in Lahad Datu, Sandakan, Kinabatangan, Beluran and Telupid. In Pitas, 2,000 pigs will be culled along with some 1,000 wild bearded pigs within a 50km radius of the town.

In infected areas, the virus is “almost everywhere inside our forest”, infecting wild pigs, says Tuuga. There is no means of stopping the animals from moving around and infecting one another. “Hopefully, there are some individuals that are immune and can survive the AFS, ” says Tuuga, adding that the Wildlife Department is working with local scientists to record the impact of the epidemic on the wild pig population.

Disinfecting pens on a pig farm in Sabah. - Sabah Agriculture and Fisheries MinistryDisinfecting pens on a pig farm in Sabah. - Sabah Agriculture and Fisheries MinistrySabah’s Veterinarian Department has yet to disclose the variant of the virus in the state or how it reached our shores. The state’s strategy currently is to protect pig farms by putting a strict SOP in place. Peninsular Malaysia does not bring in pork or pigs from Sabah so its livestock has not been affected, and Sarawak instantly closed its borders to protect its animals. There is also a ban against hunting wild pigs currently in force in Sabah.

Fear of extinction

Of the two species in Sabah, the Bornean bearded pig, Sus scrofa, is classified as vulnerable by the International Union for Conservation of Nature. It was reported that, as at March 18, at least 128 Bornean bearded pigs have died. Domestic pigs, Sus scrofa domesticus, are a subspecies of the Sus scrofa.

With the critically endangered Malayan tiger in Peninsular Malaysia at risk from diseases like canine distemper, will our wild pig population in Sabah be the next to face extinction? It’s one thing to protect the country’s wildlife from poachers but quite another to protect animals from being stalked by invisible enemies like the ASF virus.

There is now a real fear among scientists that over half of the wild pig population in Sabah may be wiped out. Is there any way to save the animals in the state, or even the populations in other countries or related species like the babirusa that is endemic to north Sulawesi in Indonesia?

‘A bottleneck event’

Based on research on the ASF, Dr Jayaraj Vijaya Kumaran predicts that the two wild pig species in Sabah may be threatened in the near future as the virus acts swiftly and the animals can die within a week of infection.

Jayaraj studies mammals and is from the Global Entrepreneurship Research and Innovation Centre, Universiti Malaysia Kelantan,

As most wild boar and pigs are very mobile, the scientist warns that the disease can quickly spread to other areas in the state. “We may be looking at a possible bottleneck event in wild populations, ” he says.

A bottleneck event, he explains, is when the death of individuals happens on a large scale in a short period of time, resulting in the total gene pool of a species, and hence its genetic diversity, dropping significantly. Upon recovery from the ASF outbreak, the genetic diversity of wild pigs in Sabah will have dropped, which is not the best condition for conservation.

A poor gene pool is one of the obstacles Sabah has faced in its unsuccessful attempts to breed and conserve the last of its Sumatran rhinos, which are now extinct in the wild.

“Genetic diversity is very important in conservation as it allows species to survive such events as a viral outbreak like the ASF, ” says Jayaraj.

He thinks it is still possible for a few individuals to be immune and survive the epidemic, as wild pigs are genetically more diverse than domestic ones.

“The proactive solution is to trap at least 30 individuals and keep them as a source population in a safe place in the event of total extinction of the animals in Borneo, ” says Jayaraj.

Forest gardeners

In Peninsular Malaysia, most people tend to view wild pigs as a nuisance: they were second only to long-tailed macaques in the number of complaints lodged with the Wildlife and National Parks Department (Perhilitan) in 2018.

However, in the jungle, wild pigs play an important ecological role. Apart from being an important food source for large carnivores like tigers, wild pigs also function as seed dispensers as they forage for their food on the forest floor.

“There is a recent study that discusses the role of pigs in forest regeneration. Scientists have proposed that these animals can be used to regenerate logged forests, ” says Jayaraj.

University of Queensland School of Biological Sciences lecturer Dr Matthew Luskin agrees. Often maligned as ecosystem destroyers, wild pigs, according to Luskin’s new study, actually help to cultivate biodiverse rainforests in their native habitats.

“Wild pigs have generally been considered a nuisance and pest in most of their native and introduced ranges by farmers, land managers and conservationists alike.

“Their negative impacts on natural and cultivated ecosystems have been well documented – they range from soil disturbances to attacking newborn livestock, ” says Luskin, who has studied wild pigs in Borneo and Peninsular Malaysia.

The joint study by Nanyang Technological University in Singapore and the United States’ Smithsonian Institution shows that wild pigs can support higher diversity ecosystems when they build nests.

Before giving birth, female pigs – or sows – build nests made up of hundreds of tree seedlings, usually on flat, dry sites in the rainforest.

“Sows select dense patches of seedlings to build nests, seedlings that are often the offspring of a nearby prolific mother tree.

“When nesting, the pigs kill many seedlings in these patches that are often dominated by a single prolific tree species, reducing the abundance of locally dominant species, but usually not a locally rare species.

“The effect provides a rare species advantage, supporting tree diversity in rainforests, ” explains Luskin, who calls wild pigs “accidental forest gardeners”.

For the study, the researchers tagged over 30,000 tree seedlings in a rainforest in Malaysia, recovering over 1,800 from inside more than 200 pig birthing nests.

“Now we are concerned that the lethal onslaught of ASF across Asia may severely reduce wild pig densities in the coming years and alter ecosystem functioning and diversity, ” says Luskin

The researcher is part of the team that warned about the disease’s potential threat against the population.

Even if, despite all odds, a few of the wild pigs in Sabah were to survive ASF, we may have to seriously consider a future with much fewer “gardeners” at work in the Bornean jungle.

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