Archives of The Cold Blooded News

The Newsletter of the Colorado Herpetological Society

Volume 29, Number 4;   April, 2002

Mystery Virus Ravages UK Frogs

by Alex Kirby

Scientists say they are now certain that the disease that has killed millions of British frogs is caused by a virus. The disease, which began in south-east England, has crossed the Scottish border, hundreds of kilometres to the north. Tom Langton, the director of the Froglife Trust, stated that: "The ends of their limb extremities, their hands and feet, drop off, they haemorrhage, open sores develop, they get thin and emaciated, and then they die."

BBC Wildlife Magazine published the research showing that a virus is responsible. The work of Froglife and the Institute of Zoology involved investigation of more than 62,000 dead frogs. Writing in the magazine, Mr. Langton says one theory for the disease's origin is a change in the source of imported goldfish. Until 20 years ago most goldfish imported to the UK came from Italy, but since then Israel and the US have dominated the trade.

In the US, bullfrogs breed alongside the goldfish enclosures, and are often attacked with shotguns to stop them competing for food pellets. Mr. Langton writes: "Bits of bullfrog could be eaten by a goldfish that is netted and flown off for quick distribution to British garden centres."

"It's a complex situation and the exact causes are still not known. Slug pellets, vehicle emissions, and changing weather patterns may play a role in reducing frogs' resistance to the virus; the isolation of urban frogs and inbreeding could also be a factor. More research is needed urgently."

Froglife says the disease was first seen to be increasing in suburban London gardens in the late 1980s. "Typically, adult frogs are seen to be dying over several weeks, resulting in dozens, or even hundreds, of deaths." Reports of the virus reach a peak in July and August. Large-scale frog mortalities also occur in late winter and are usually caused by a garden pond freezing over, which can suffocate male frogs hibernating at the bottom. "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."