Certain people are more likely to contract the infectious disease leprosy because of their genetic make-up, scientists have revealed.

A study of nearly 500 family members living in south India has found a genetic influence that could explain why leprosy tends to run in families.

Geneticists are now hunting for a specific susceptibility gene that could one day lead to new treatments for a disease that has long afflicted humanity.

Leprosy was recognised in the ancient civilisations of China, Egypt and India, and was mentioned in written records as early as 600 BC.

The germ that causes the disease is transmitted during close contact with infected persons. Leprosy is curable in its early stages but if left untreated can lead to permanent damage of the skin, nerve, limbs or eyes.

The disease has now been wiped out in 98 countries but there are still about 800,000 cases of leprosy around the world, half of them in India.

Doctors have long observed that the disease tends to run in families despite being caused by an infectious agent. But this is the first time that a definite genetic link has been located and narrowed down to a specific stretch of DNA.

The study was carried out by Madurai Kamaraj University, India, in collaboration with researchers at Oxford University, UK.

They are now hunting for a specific leprosy susceptibility gene or genes that could explain why some families are inflicted by the disease while others escape it.