Poultry farmers have voiced fears that bird flu could wipe out their businesses and pose a threat to their families.

Experts have identified a list of migratory birds which could bring the killer virus to Sussex, including the wigeon, teal, pochard, mallard, pintail, shoveler and tufted duck.

Farmers are preparing for the worst amid virologists' warnings that the spread of the H5N1 strain is inevitable.

Richard Barton, 37, manager of six organic poultry farms containing 45,000 laying hens, in north Chailey, Ditchling, Wivelsfield Green and Barcombe, said he was extremely anxious for his family, 20 staff and birds.

He said: "There was a different strain of bird flu in Holland three years ago and that decimated the industry over there. H5N1 is an even more serious strain of avian influenza and we are in close contact with the hens every day.

"If our hens did catch H5N1, that would mean 20 staff losing their jobs and six farms having to close. We are also one of the biggest organic egg suppliers in the country, so suddenly organic eggs would be in very short supply throughout the supermarkets."

Brian Masters looks after 6,000 organic egg-laying hens at Little Teagues Farm, in Scaynes Hill, near Haywards Heath, with his wife and two staff.

He said: "We have the usual array of foot dips and are monitoring who comes on to the farm and keeping visitors to a minimum at the moment. That is to stop any potential disease spreading."

The H5N1 strain's march westwards, from south-east Asia to Russia and Kazakhstan, was confirmed on a poultry farm last week.

The virus can only be passed from bird to bird and bird to human. But scientists have warned it could mutate into one which humans could catch from each other.

The Sussex branch of the Royal Society for the Protection of Birds (RSPB) said the main birds migrating here for the winter might include wigeon and teal from Russia, Siberia, Iceland and Scandinavia.

A prominent route for wigeon to reach Sussex is from Siberia or Russia through the Baltic countries, then to Denmark and Holland and then Chichester harbour, Pagham harbour or the Cuckmere Valley.

Another migratory bird is Bewick's swan which, after starting out from Siberia, has in the past stopped off at Estonia and the Netherlands before reaching the Arun Valley in Sussex.

The RSPB is watching out for unusual events where large numbers of sick or dying birds have been reported.

Spokesman Adrian Thomas said: "The risk of migratory birds bringing avian flu into the UK is low and, even if it did happen, the risk to humans would be low.

"There are no records of humans contracting flu from wild birds. The H5N1 virus originated in domestic poultry in south-east Asia, and the only way humans contract it is by close contact with the poultry."

Hospitals are awaiting instructions from the Government before planning detailed responses to a possible pandemic.

A spokeswoman for Royal Sussex County Hospital said: "It is too early to tell how the trust will be affected by bird flu as the Department of Health is still establishing the possible health risks if the virus reaches the UK and then affects humans."