Canine distemper virus: An emerging disease in rare Amur tigers

Aug 13, 2013

Rare Amur tigers in Russia are succumbing to infection with canine distemper virus (CDV), a pathogen most commonly found in domestic dogs, according to the authors of a study published in mBio, the online open-access journal of the American Society for Microbiology.

Pressure from poaching, decimation of their prey base, and have diminished the population of Amur tigers (also called Siberian tigers) to fewer than 500. In the study, a team of scientists from the US and Russia show that CDV infected and caused fatal neurological disease in members of this critically endangered species. They estimate that the virus has killed at least 1% of Amur tigers since 2009.

"Losing 1% of an endangered population is pretty significant," says corresponding author Denise McAloose, Head Pathologist at the Wildlife Conservation Society in The Bronx, New York. "And these losses represent only the deaths we know about. I imagine that there were others that we just never saw," says McAloose.

Since 2001, several rare Amur Tigers have exhibited a set of strange behaviors. Normally a reclusive species, tigers have been seen entering villages and wandering onto roads in the Russian Far East, stumbling, emaciated, and unafraid of humans. (One example can be found below). In each of the documented cases, the tiger eventually died or was destroyed after its condition worsened. Early findings showed that at least one of the tigers was infected with a member of the morbillivirus family of viruses, but conclusive answers had evaded scientists and until now.

This video is not supported by your browser at this time.

Using from five wild Amur tigers that died or were destroyed due to neurological disease in 2001, 2004, or 2010, McAloose and her colleagues proved that infection with CDV, a type of morbillivirus, is to blame for the deaths of two of the tigers and caused a serious infection in a third. Under the microscope, the brains of the two tigers that died of CDV infection were riddled with lesions, indicating they suffered from severe viral encephalitis, consistent with their clumsy, abnormal behavior. Molecular analyses to identify CDV-specific proteins and immunolabelling with CDV-specific antibodies confirmed that CDV was present in these tissues. A gene for a CDV-specific gene was detected in the third tiger.

The problem isn't limited to one location, says McAloose. The three tigers that tested positive for CDV were distributed across the Russian Far East.

"That tells us this is a disease that is distributed all across Amur tiger range," McAloose says. "And it also appears to be a relatively new threat to tigers since blood samples from wild tigers prior to 2000 tested negative for antibodies to the virus".

But how do tigers contract a CDV infection? Relatively few domestic dogs in the Russian Far East are vaccinated against CDV, McAloose says, and tigers do kill and eat dogs, so they represent one possible source. But domestic dogs aren't the only suspects.

"In the Russian Far East, are one of the biggest concerns, but other species, like raccoon dogs or foxes, can also harbor the disease," says McAloose.

McAloose and her colleagues are now working on collecting samples from dogs and small wild carnivores in the Russian Far East to get a more complete picture of the various strains of CDV in circulation in the hopes of linking tiger infections to a source, knowledge that would hopefully aid in preventing more infections among tigers.

"The situation is quite serious", says McAloose, and when asked if CDV could spell the demise of Amur , she says, "It's possible."

"It's the first infectious disease that we know is a significant risk to Amur tiger survival," says McAloose.

Explore further: NYSCF Research Institute announces largest-ever stem cell repository

add to favorites email to friend print save as pdf

Related Stories

Nepal's Royal Bengal tiger numbers soar

Jul 29, 2013

Nepal's number of Royal Bengal tigers in the wild has soared 64 percent to 198 in just four years, according to a government survey released Monday.

White tiger mystery solved

May 23, 2013

White tigers today are only seen in zoos, but they belong in nature, say researchers reporting new evidence about what makes those tigers white. Their spectacular white coats are produced by a single change ...

Rare Sumatran tiger cubs born at US zoo

Aug 08, 2013

Two rare Sumatran tiger cubs were born this week at the National Zoo in the US capital, in what zookeepers described Thursday as a conservation victory for the critically endangered cats.

Recommended for you

Crowdsourced power to solve microbe mysteries

21 hours ago

University of New South Wales scientists hope to unlock the secrets of millions of marine microbes from waters as far apart as Sydney's Botany Bay and the Amazon River in Brazil, with the help of an international ...

Reading a biological clock in the dark

Oct 21, 2014

Our species' waking and sleeping cycles – shaped in millions of years of evolution – have been turned upside down within a single century with the advent of electric lighting and airplanes. As a result, ...

User comments : 0