A beautiful Sumatran tiger. (c) www.zoo.org.au

As reported earlier on ZME, as little as three thousand tigers are currently alive today in the wild from six subspecies, or thirty times fewer than 100 years ago. Loss of habitat and poaching are the main drivers that brought these majestic cats at the brink of extinction. Now, a new threat might put tigers at an even greater risk: a virus that typically affects domestic dogs has mutated and is seemingly affecting big cats as well.

Canine distemper virus (CDV), closely resembling measles, was first described at the beginning of the 20th Century and has been cited as contributing to the demise of the thylacine, commonly known as the Tasmanian tiger. In the past few decades, however, the virus has evolved and apparently it can now infect marine mammals like seals and big cats.

John Lewis, director of Wildlife Vets International, recently spoke to the BBC and recollected his findings working with Indonesian vets who have been reporting several cases of CDV infected tigers in the area. The news is extremely startling, considering the precedents. In the mid-1990s, in the Serengeti, Africa, about 30% of the lions died from CDV, which came from dogs in surrounding villages. Dr. Lewis speaks of other known cases of infected big cats:

“It has also been recognised in the Asian big cat populations,” he added.

“Since 2000, in the Russian Far East, there have been a few cats reported as behaving strangely and coming into villages, apparently not showing much fear towards people.

“In the past few years, tissue from at least a couple of those cats have now been confirmed as showing the presence of CDV infection.

“There have not been too many cases at the moment, we think about three or four, but we think there could have been more that have gone undiagnosed.”

Lack of fear, especially of humans, is one of the number of symptoms CDV infected animals exhibit. These include other neurological disorders like seizures and respiratory problems, such as pneumonia, that often lead to death. Although it was assumed the cause of CDV infection in tigers was a result of coming into contact with dogs carrying the virus, Dr Lewis said that a research project was under way to look at the source of CDV in Amur tigers (also known as Siberian tigers) in the Russian Far East.

After speaking to Indonesian vets in the island of Sumatra, where a distinct population of tigers that only live here and number a mere 700 individuals, Lewis reckons CDV could already be present in the population of the critically endangered Sumatran tiger. They told him that they had seen strange behaviour displays by tigers, such as the big cats coming into villages and losing their fear of people.

“To me, that suggests that distemper is already beginning to have an impact on tigers in Sumatra,” he warned.

“But before you say ‘yes, that is definitely the result of CDV’, you need diagnostic testing of brain tissue.

“The big threats facing tigers are habitat loss and degradation and poaching, but I think the third big threat now is likely to be disease, particularly one like CDV.”

In September, Lewis plans to return to Sumatra with a team of vets where they’ll sample tigers and dogs alike for the virus.

“We also need to thrash out what samples need to be taken from domestic dog populations.

“We need to work out where we can send these samples for laboratory testing. We need to work out how we are going to store and move these samples.

“Once we have got that nailed down then we start work and try to design some sort of mitigation strategy, and that won’t be easy.”