A man is fighting for his life with a suspected case of rabies after being bitten by a rabid bat, making him probably the first person in Britain to contract it this way for a century.

The unnamed man from Angus handled bats as part of his volunteer work. He is being treated in an isolation ward in the intensive care unit of Ninewells hospital, Dundee, where his condition is described as critical.

Doctors said the case is still only suspected rabies, but tests could prove the initial clinical diagnosis of the virus and whether his symptoms are advanced. If confirmed, rabies is ultimately a fatal disease.

The test results are expected to be known tomorrow. If the patient dies, it will be the first death from an infected bat with rabies in the UK since 1902.

It is understood the worker was not immunised against the strain of rabies - European Bat Lyssavirus.

Dr Drew Walker, director of public health at NHS Tayside, said it was a rare disease and there was minimal risk to the public. He said: "First of all we need to have confirmation this is a case of rabies but it is very easy for people to avoid becoming infected.

"These measures are simply avoiding handling bats under any circumstances. If they come across bats which need help they should contact experts."

There were no immediate plans to cull any bat populations or colonies as a result of the suspected case.

Dr Dilip Nathwani, consultant physician in infectious disease, said the patient was extremely ill and that diagnosis was very difficult because the illness was so rare.

Of the two types of rabies, Dr Nathwani said the worker could have the less common form of paralytic rabies, a neurological illness whose symptoms are fever and paralysis from the feet upwards.

The illness could be prevented by vaccines given before exposure or after the virus has been taken on board. Officials today declined to comment on whether the patient had been vaccinated.

Most licensed workers whose work brings them into close contact with bats are vaccinated as a precaution, as well as travellers going abroad where rabies and bats are more common.

The patient's family has been informed of the possible diagnosis and were being offered advice and vaccination, as were clinical staff closely involved in his treatment.

However, Dr Nathwani said: "There have been no cases of person-to-person rabies transmission recorded anywhere." The risk of the virus spreading from one person to another was purely "theoretical", he said.

Health officials would only say the man had been in hospital for "less than one month". "But he was not moved on to an isolation ward immediately on admittance," Dr Nathwani said. Dr Nathwani said even if tests proved negative that would not necessarily rule out the clinical diagnosis of rabies.

Colin Galbraith, chief scientist at Scottish Natural Heritage, said the worker had been known to his organisation and had worked with bats for a "considerable length of time".

The worker could have been infected from as long ago as two years because the incubation period varies, although the infection is more likely to have occurred within the last few months.

Meanwhile, the bat that may have passed on the infection could have flown from mainland Europe and not necessarily be from the UK.

Mr Galbraith said Scottish Natural Heritage would look at guidelines for workers handling bats in light of the suspected infection. "We will certainly be looking at what bat workers do in general when they are in close contact with these animals."

He added that investigations were being carried out as far as possible to ascertain when and where the worker may have been infected by the bat. A warning was issued earlier this year that British bats may carry the rabies virus. It is thought just 50 people in Scotland are licensed to handle bats, which are protected species.