LONDON, Nov 28 (Reuters) - Britain's toad population could face extinction in some areas within 10 years due to an infectious fungal disease, scientists said on Wednesday.

Deadly Batrachochytrium dendrobatidis was introduced to Britain with the release of non-native North American bullfrogs. They have since been exterminated but the disease remains.

New mathematical models developed by researchers at Imperial College London and the Institute of Zoology point to the disease having a potentially devastating impact in Britain where it has so far been detected only in the southern county of Kent.

The big unknown is just how long the fungus, which lives on the skin of host amphibians, can survive on its own in water. Scientists fear it may be a very long time.

"We start to see dramatic effects if the chytrid (fungus) lives for longer than seven weeks outside the host," said Mat Fisher of Imperial College.

"We strongly suspect that it can live for longer because of the devastating effect it has had elsewhere, and the new models show that this would be very bad news for toads in this country."

If the fungus is able to live outside the host for a year, there would be a severe decline in the overall population of the European common toad (Bufo bufo) in Britain and, in some places, extinction in 10 years, the models suggest.

The disease has already destroyed entire amphibian populations in Central and South America, and Australia, and is a growing problem in some parts of Europe. Scientists have linked its spread to global warming.

Luckily, the common British frog (Rana temporaria) is resistant to the disease.

The findings by Fisher and his colleagues were published in the journal Proceedings of the Royal Society. (Reporting by Ben Hirschler; editing by Robert Woodward)

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