A significant step towards understanding the genetic make-up of a parasite which causes leishmaniasis - a flesh-eating disease spread by the bite of a female sand fly - has been made by a team of researchers from the University of Glasgow. The study is published in the journal Genome Research.
Approximately 350 million individuals in 88 countries, including Afghanistan, Syria, Saudi Arabia, Peru, Iran, Brazil and parts of china, are at risk of catching the disease.
There are 21 species of the parasite in two different forms: Cutaneous leishmaniasis, which affect the skin and mucus membranes and systemic or visceral leishmaniasis, which affect the entire body. Symptoms include, skin sores, difficulty breathing, ulcers and erosion in the mouth, gums, lips, and tongue, fever, diarrhea, as well as potentially fatal infections of the liver and spleen. The disease, which infects white blood cells, is usually treated with chemotherapy.
Investigators have now been able to examine the genome of different species, which in turn will assist them to better understand how different forms of the parasite develop as well as finding better treatments.
The investigation project led by researchers at the Wellcome Trust Centre for Molecular Parasitology at the University of Glasgow with colleagues at the University of York and the Sanger Institute in Cambridge received £1m in funding from the Wellcome Trust and was aimed at furthering understanding what the World Health Organization (WHO) classifies as a neglected tropical disease.
According to the WHO, up to 12 million individuals worldwide are currently infected with the disease, with an estimated one to two million new cases occurring each year.
After examining and sequencing the genomes - the complete set of genes within an organism - of 4 different species of the parasite, in addition to different isolates of the same species, the researchers found that genetic content for all four species was similar, but were arranged in different ways.
Professor Jeremy Mottram, of the University of Glasgow, explained:
"There are many species of the parasite that can cause different forms of the disease and require different forms of treatment. This can also cause problems for diagnosis.
We discovered that different species of the leishmania parasite share a large number of similar genes, but the genomes are structured in different ways and with extensive variation in the number of chromosomes - the pieces of DNA that store genetic information about an organism."
Dr Nick Dickens, a genome specialist at the University, stated:
"It is largely the different genome structure, including the copy number of genes and as a result, the amount of proteins expressed by these genes that cause differences between the species and hence clinical forms of the disease.
A combination of many genes within a parasite can be responsible for the disease, so identifying and understanding the genetic and structural differences in the species could help develop improved treatments."
The parasite is a form of trypanosomatid protozoa related to parasites that cause sleeping sickness and Chagas' disease.
The disease mainly affects poor individuals in developing countries. Over 90% of the severest form of the disease occurs in Brazil, Bangladesh, Sudan, Nepal and India.
Numerous British Soldiers deployed in Afghanistan have been infected with the disease as well as British television presenter and adventurer Ben Fogle, who was treated for the disease in 2008.
The disease is named after William Boog Leishman, the Scottish pathologist and British Army Doctor and graduate of the University of Glasgow who discovered the parasite.
Written by Grace Rattue