By Mark
Kinver
Some of the
world's rarest big cat species are facing a potentially deadly threat from a
virus carried by domestic dogs, a wildlife expert has warned.
Canine distemper virus has been confirmed in a
number of Amur tigers
John Lewis, director of
Wildlife Vets International, said there was evidence that Indonesian tigers
were at risk.
Canine distemper virus has
evolved in recent decades from infecting only dogs to affecting other animal
groups.
Dr Lewis plans to work with
Indonesian vets to develop a strategy to protect the nation's tigers from the
virus.
A close relative of
measles, Canine distemper virus (CDV) 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 as a result of the black
stripes on its back).
"If you wind the clock
back about 30 or 40 years, it was a dog disease - it was a canine virus and
only affected dogs," Dr Lewis explained.
"But in the
intervening years, the virus has evolved and has changed its pattern of animals
it can infect to include marine mammals (such as seals) and big cats."
Anecdotal evidence suggests
CDV is already affecting critically endangered Sumatran tigers
Reservoir
dogs
He told BBC News that CDV
needed a reservoir, like a population of dogs, to remain effective as a
pathogen.
These conditions were
present when the first case of the disease affecting wild big cats was
documented, he recalled.
"In the mid-1990s, in
the Serengeti, Africa, about 30% of the lions died from CDV, which came from
dogs in surrounding villages.
"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."
While some tigers appear as
if they are able to build up a reasonable immunity response, most of the
animals do succumb to the disease if they are exposed to the virus.
Dr Lewis explained that
symptoms manifested themselves in a number of ways:
"Some will die as a
result of respiratory problems, such as pneumonia for example.
"Some will have
neurological problems, such as losing the fear of people or having
seizures."
But, he added: "We do
not have enough information on CDV in tigers to know what percentage go on to
die; we just have a little bit of data from zoos and a little bit of data from
the wild.
"There are a lot of
cases of distemper in the region and tigers are partial to eating dogs.
"For a tiger to take a
dog on the periphery of a village is not usual at all, so you do have the
circumstances that would bring tigers into contact with CDV."
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.
Worrying
signs
The behaviour change in
tigers was particularly worrying, Dr Lewis observed.
"This puts them at big
risk because they lose their fear of poachers or they bring themselves in
situations of conflict, such as playing with traffic."
On a recent visit to the
Indonesian island of Sumatra, he said conversations with local wildlife vets seemed
to indicate that 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."
The Sumatran tiger is only
found on the island and population estimates suggest that there are fewer than
700 left in the wild, of which only 40% are viable mature individuals.
Dr Lewis is returning to
Sumatra in September to bring together all the vets from all the different
areas that come into contact with tigers.
"The goal is to thrash
out a very simple way of deciding what samples need to be taken from all tigers
that are handled by humans throughout Sumatra, in order to help us with
diagnostics," he explained.
"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."
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