A mysterious epidemic triggered by a deadly virus has blinded thousands of kangaroos -- report Australian scientists -- leading many to death through starvation, blundering into traffic and drowning in rivers.

To put the kangaroos out of their misery, some have been shot down. Reports of the deaths began appearing late last year. Says Tim Fraser, a National Parks and Wildlife Service ranger in Berri, South Australia: "Over the past 6 weeks or so, it has increased dramatically. It's now a very serious problem."

The disease, which irreparably damages retinas and optic nerves, is believed to be transmitted by mosquitoes or flies. Other theories put the blindness down to a vitamin A deficiency, or poisonous plants eaten because drought has left a shortage of feed.