Deadly virus pushing tigers toward extinction

Adding to the already devastating pressures of habitat loss, poaching and depletion of prey species, a new threat to tiger populations in the wild has surfaced in the form of canine distemper virus (CDV).

CDV has the potential to be a significant driver in pushing the animals toward extinction, said a study from the Wildlife Conservation Society (WCS).

Smaller populations of tigers are more vulnerable to extinction by CDV, the findings showed.

Populations consisting of 25 individuals were 1.65 times more likely to decline in the next 50 years when CDV was present.

"Many tiger populations have become smaller and more fragmented, making them much more susceptible to diseases such as CDV," said Dale Miquelle, program director, WCS Russia.

The authors evaluated the impacts of CDV on the Amur tiger population in Russia's Sikhote-Alin Biosphere Zapovednik (SABZ), where tiger numbers declined from 38 individuals to 9 in the years 2007 to 2012.

In 2009 and 2010, six adult tigers died or disappeared from the reserve, and CDV was confirmed in two dead tigers.

The scientists used computer modeling to simulate the effects of CDV infection on isolated tiger populations of various sizes and through a series of transmission scenarios.

The results are profoundly disturbing for global wild tigers given that in most sites where wild tigers persist they are limited to populations of less than 25 adult breeding individuals.

The findings appeared in the journal PLOS ONE.