Malayan tigers face new threat: Extinction-level virus could wipe them out

The three-minute long viral video of a tiger roaming – “unafraid” and “harmless” – among villagers in Mersing, Johor, in early March looked familiar to us. In many ways it was a repeat of an incident in Dungun, Terengganu, over 330km away and some six months earlier, in July 2019, which was also caught on video and went viral.

In both cases, the tigers – found close to the villages and the villagers – were disoriented and underweight.

The two animals were also later found to have died from the canine distemper virus or CDV.

Awang Besul, the “tame” male tiger in Dungun, died of the disease despite efforts by Wildlife and National Parks Department (Perhilitan) officers to treat it upon capture. The tiger in Mersing was found dead and decomposing on a hillside in Ladang Aramijaya on March 4.

At that time, although the tiger had been showing signs of having been infected by CDV, authorities could not be sure until after a necropsy had been conducted.

In a statement to The Star on March 30, the department confirmed that the second tiger in Mersing had indeed died of CDV.

While Malaysia, along with the rest of the world, is caught up in the fight against Covid-19, another virus is threatening the population of our wild tigers.

Being unafraid of humans is a behaviour symptomatic of the disease due to brain damage wreaked by the virus. Other symptoms are respiratory problems, diarrhoea, seizures and loss of motor control.

Although CDV is primarily associated with dogs and wild canines like wolves and foxes, it can also infect other carnivores, such as ferrets, pandas, seals and, in some cases, even humans.

Catching the tiger Awang Besul in Kampung Besul Lama, in Dungun, Terengganu, was a tame affair as the canine distemper virus infecting it had affected its brain, leaving it unafraid of humans. — Perhilitan

With the last official count of the wild Malayan tiger population at less than 200 in our jungles, putting them on the brink of extinction, will it be a viral epidemic that finally rings the death knell for the species?

“I wouldn’t say (the population) is doomed but yes, it is in danger, particularly populations that are isolated, ” remarks Dr Mark Rayan Darmaraj, WWF-Malaysia tiger lead.

“The Malayan tiger is already declining due to poaching, habitat loss and fragmentation or degradation, as well as prey loss – and now CDV seems to be emerging as yet another threat.”

Dr Mark Rayan Darmaraj, WWF-Malaysia tiger lead

However, there is a saving grace for Malayan tigers, as Dr Darmaraj puts it, in that transmission of the disease is faster within a pack of animals. And tigers are not pack animals, unlike, say, wolves.

“Tigers are mainly solitary, except when mating, with young or, at times, when dispersing as sub-adults, ” he explains.

But the disease, he warns, can still be quickly transmitted from other groups of carnivores that come into contact with tigers.

“Very often, tigers have been known to kill dogs, either to eat them or to reduce the likelihood of the tiger’s presence being revealed, as dogs bark and alert people of a threat.

“This would apply to other wild carnivores such as leopards and wild dogs in Malaysia, ” says Dr Darmaraj.

Sick In Siberia

This is not the first time that vulnerable wild tiger populations have been hit by CDV. In 2001, there were reports of endangered Siberian tigers (Panthera tigris altaica) in distress in Russia; weak, disoriented, underweight and incapable of hunting, four of the animals had to be put down after they wandered into a town.

It was only in 2011 that the condition was traced to CDV. The highly contagious disease is caused by the canine morbillivirus from the Paramyxoviridae family, which is closely linked to the human measles virus. By 2013, CVD had infected 15% of the more than 400 Siberian tigers in Russia’s far east.

A similar viral outbreak has been reported among wild tigers in India and there are fears that tigers much closer to Malaysia, in Sumatra, Indonesia, may be at risk as well.

Around the mid-1990s, CDV was reported to have killed about one-third of the lions in the Serengeti in Africa.

It was thought then that the lions and tigers must have caught the disease from eating infected dogs or other carnivores, as it is not unusual for disease to jump from one species to another. A case in point is the Malayan tiger in the Bronx Zoo in New York City that was infected with Covid-19 from one of the staff.

Targeted Studies Needed

But since then, some scientists have linked the prevalence of CVD with dwindling populations in the wild, because the Siberian tigers, like Malayan tigers, are also endangered although not as critically.

Dr Darmaraj does not think this is necessarily true, though.

“The prevalence could just be at the interface where there are human-caused conditions allowing the disease to be transmitted from domesticated or feral animals to wild animals, usually as an edge effect. (Feral animals are domesticated animals that have gone wild and live on the fringes of human habitation and are different from wild animals.)

“These could be on the fringes of the forests and not affect the core areas of a population, ” he points out.

‘Tame’ tiger Awang Besul being cared for by a Perhilitan staff member at the National Wildlife Rescue Centre in Sungkai, Perak. The tiger, which was infected with the canine distemper virus, caught on July 19, 2019, and died on July 23. Photo: Perhilitan

Dr Darmaraj is now calling for more targeted studies to collect baseline data on CDV cases in wild carnivores in Malaysia.

“This is needed to better understand the role of feral or domestic animals as contributors to a local CDV reservoir, ” he says.

Because feral and domesticated dogs are known to be carriers and could be a source of transmission, Dr Darmaraj says that for a start, during an outbreak, dogs living near or in the fringes of the forest, particularly in villages, plantations and logging camps, can be tested for the presence of CDV antibodies.

If they are found to be positive, they must be vaccinated, he says.

But this is only a short-term measure.

“Ideally, you would want to devise a disease surveillance and management strategy that not only looks at managing an outbreak but also minimises future risks, ” he points out.

Vaccination Programme

Dr Darmaraj says, to his knowledge, scientists dealing with the viral outbreak in Russia have used relatively similar measures, except in the case of Siberian tigers because they range over long distances and have large home ranges spanning interconnected landscapes.

“In general – not just in Russia – even if tigers are affected and a proportion of the population dies off, the existence of interconnected forest landscapes will definitely help the process of recovery, ” he adds.

That’s why, ultimately, it is critical for there to be connectivity through the Central Forest Spine of peninsular Malaysia to reduce the likelihood of populations being wiped out, Dr Mark points out. Not just by CVD but by all sorts of threats.

“This is because the process of tiger dispersal is facilitated by the presence of corridors that connect large forest complexes, allowing for tigers to move across their range and establish new home ranges.

In other words, having large interconnected landscapes is important to reduce the likelihood of diseases wiping out a population. Meanwhile, Perhilitan says it has already planned several programmes and studies in collaboration with other agencies to ensure that wild populations in the areas involved are not threatened by CDV.

“A vaccination programme for pet dogs is one of the programmes being planned in cooperation with other agencies.”

This article was published on 21 April 2020 by Sim Leoi Leoi | The Star Online

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