Evidence is growing that garden birds in East Anglia are at risk from the spread of a deadly disease, experts warned last night .

Evidence is growing that garden birds in East Anglia are at risk from the spread of a deadly disease, experts warned last night.

Hundreds of garden birds, including finches, sparrows, doves and pigeons, have been reported to have been struck down by the lethal parasite in the west of the country over the last few weeks.

But officials in Norfolk fear that the contagious trichomonas parasite, which is also known as "canker," has arrived in the county and are urging people with bird feeding stations to be on their guard.

Post-mortem examinations on a number of garden birds, carried out by the British Trust for Ornithology (BTO), based in Thetford, have found that the disease has thrived during the hot summer.

So far the organisation has received reports of 600 dead greenfinches across the country, but last week was told of a trichomonas case in Wroxham.

The RSPB in East Anglia has also received isolated reports.

Paul Stancliffe, from the BTO, said it looked like the disease originated in the West Midlands and spread to the North West, Lincolnshire and now East Anglia.

"BTO scientists believe that this summer's weather may have triggered a more substantial outbreak. From reports received so far, greenfinches seem to be the hardest hit.

"There is a chance that the cold weather will kill the disease, but we want to track where this is going on and urge people to keep a clean bird feeding stations," he said.

The parasite, which can live outside a host for up to five days, affects species that congregate around feeding stations, including greenfinches, chaffinches, house sparrows, and pigeons, and is transferred via regurgitated food and contaminated seed and water.

Infected birds appear lethargic, with fluffed-up plumage and may also have difficulty swallowing and have a severe swelling of the neck.

Chris Durdin, spokesman for the RSPB in East Anglia, said the spread of trichomonas was a "concern" and the society was keeping a close eye on its development.

"It seems to spread unless action is taken, so people need to be aware of the symptoms and solutions. If it gets out of control, you never know, but at present levels it will not affect populations. The cold would likely kill it, but we are predicted to have a mild and wet winter, which would be counter productive," he said.

Both bird organisations are urging householders to prevent the disease by cleaning feeding stations and bird baths with a light disinfectant, to change drinking water daily, and to move feeders frequently to avoid a build-up of contamination.

Reports of diseased garden birds should be made to the Garden Bird Health Initiative on 0207 449 6685 or for more information, visit www.bto.org or www.rspb.org.uk