A groundbreaking study of Scots' DNA is being launched to discover why the nation has the highest rates of multiple sclerosis in the world.

It is hoped the research, which involves scouring the genes of hundreds of people, will explain why patients contract the devastating disease and help the development of new treatments.

The populations of Orkney and Shetland are the focus of the investigation as MS is more common in the two island communities than anywhere else.

Residents who suffer from the illness will be asked to give blood, as well as locals who have no history of the disease, so scientists can compare the samples. They hope to untangle the genetic code which makes people vulnerable to MS and see if their blood responds differently to a virus which it is thought might trigger the illness.

Dr Jim Wilson, a population geneticist at Edinburgh University who is leading the study, said: "We hope to unravel the mystery as to why rates of MS are so high in Orkney, Shetland and Scotland and also to provide possible answers to patients who suffer the disease around the world."

Edinburgh University is already working on new drugs to combat the effects of MS at their dedicated research centre, which was set up using a grant from author JK Rowling. Dr Wilson is based in the university's MRC Human Genetics Unit and was researching the genetic traits which predispose people to heart disease on Orkney four years ago when he became interested in MS.

He said: "As we visited people on the doorstep everyone asked us why we were not studying MS. It is very high up in people's consciousness in Orkney because so many people have it. I felt an obligation to do it."

He has obtained a grant of £215,000 from the MS Society Scotland and is launching the project this month.

First, he will identify the exact number of patients with MS on the two island groups. A study from the 1970s suggests there are more than 60 sufferers on Orkney alone, but Dr Wilson believes the numbers may have increased.

He then intends to recruit every patient if possible and twice as many people of a similar age and background without MS for DNA testing. His team will analyse these samples to see if a variation of the gene DR15, which is already associated with the disease, is common on the islands. In addition they will search for previously undiscovered genetic variations.

Dr Wilson said: "We will be looking at more than 300,000 genetic markers using the most up-to-date technology available."

Finally, in collaboration with Aberdeen University, he plans to study how introducing elements of the virus which causes glandular fever affects white blood cells taken from both the patients and the controls, to see if there is a difference. There is reason to believe the Epstein-Barr virus may play a role in the onset of MS.

Dr Wilson, who is from Orkney, added: "There has not been a lot of immigration in Orkney so it is much easier to pick out the signal of a genetic effect from all the background noise."

Mark Hazelwood, director of the MS Society Scotland, said: "Scotland has the highest prevalence of multiple sclerosis in the world and we believe it must make a major contribution to international research efforts to understand it."

Dr Wilson wants to recruit MS patients born in Orkney and Shetland who have moved elsewhere for the research. They are asked to ring 0131 651 1643 or e-mail orkney@ed.ac.uk.