Experts discover origin of virus killing Britain's frogs

A mystery virus that has ravaged the frog population of Britain may have entered the country inside imported goldfish, scientists said yesterday.

Naturalists have reported hundreds of cases of dying frogs over the past year, suffering from a disease that causes their paws and feet to drop off.

Tom Langton, director of the Froglife Trust, said that the epidemic is worse than myxomatosis, the plague that destroyed the rabbit population 40 years ago. He said: "It's a living death. The animals take a considerable time to die, and there are some indications that their numbers are permanently depressed in some areas."

An investigation of more than 62,000 dead frogs by scientists at the Institute of Zoology in London and the Froglife Trust has concluded that the culprit is an unknown viral infection. Writing in BBC Wildlife magazine, Mr Langton said that 20 years ago goldfish were imported from Italy but now they mostly come from Israel and the United States, where bullfrogs are often blasted with shotgun pellets to stop them competing for fish food.

"Bits of bullfrog could be eaten by a goldfish that is netted and flown off for quick distribution to British garden centres," Mr Langton said. The American bullfrogs may have been infected with the same virus, he added. There a worldwide decline in frog numbers, along with other species of amphibians, and a range of causes have been suggested, from infections to loss of habitat. This particular disease in Britain first appeared in London gardens in the late Eighties. Since then it has spread north and has crossed the Scottish border.

Mr Langton said: "We have found no evidence of the disease affecting people, pets or other pond life. Most people report that toads, newts and fish in a pond where frogs are dying appear totally healthy."

He said that a number of other factors may also be playing a role in making frogs more susceptible to infection. "It's a complex situation and the exact causes are still not known," he added. "Slug pellets, vehicle emissions and changing weather patterns may play a role in reducing frogs' resistance to the virus," he said.