The black fever parasite migrates to organs such as liver, spleen and bone marrow and if left untreated will almost always be fatal.
Symptoms of the disease, known as kala azar in India, include fever, weight loss, mucosal ulcers, fatigue, anaemia and substantial swelling of the liver and spleen.
Leishmaniasis affects 12 million people and there are an estimated 1.5 million new cases annually, mainly in India, Bangladesh, Nepal, Sudan, South Sudan, Ethiopia and Brazil, the journal Nature Genetics reports.
Jenefer Blackwell, professor and head of genetics at the Telethon Institute for Child Health Research, University of Western Australia co-authored the study which has uncovered a single major genetic risk factor for visceral leishmaniasis.
Scientists from India, Brazil, Britain, US and Australia, Blackwell identified variation in a specific region of the major immune response locus, known to immunologists as the major histocompatibility complex (MHC), as the single most important genetic risk factor for disease, according to an university statement.
The researchers compared genomes of 1,346 people suffering from disease in India and Brazil against those of 2702 healthy controls.
The findings were confirmed in an independent cohort of 941 cases and 990 healthy controls (not suffering from black fever) from India.
Teams in Australia, Britain and the US are using the results to study the way the immune system interacts with the disease in mice.
"Earlier genetic studies of visceral leishmaniasis in inbred mice allowed us to clearly demonstrate the importance of the MHC in regulating this disease," Blackwell said.
