After sequencing the complete genome of Leishmania donovani, a parasite causing one of the most important tropical diseases after malaria, a team of scientists from Europe, Nepal, and India, has identified a series of mutations specific of ‘superparasites’ and developed a simple assay that should allow tracking them anywhere.
Leishmania is a unicellular parasite that is transmitted through the bite of sandflies and occurs mainly in Latin-America, East-Africa, Asia and countries around the Mediterranean Sea. The parasite causes a disease called leishmaniasis which can range from self-healing cutaneous to deadly visceral disease, depending on the infecting species.
The WHO estimated up to 1,6 million of new cases of leishmaniasis every year, affecting essentially the poorest of the poor. In comparison to these figures, the hundreds of imported cases reported among travelers appear a drop of water in the ocean. Some of these parasites are more dangerous than others, among them those causing visceral leishmaniasis, a clinical form which is lethal in the absence of treatment.
Recently, the same team reported among these dangerous microbes, the existence of ‘superparasites’ in the Indian sub-continent, which are drug resistant and at the same time also better equipped to cope with our immune system. To our knowledge, it is the first time such a doubly armed organism is found in nature. These superparasites could jeopardize current efforts to control this devastating disease.
Now, the team has unraveled the DNA code of Leishmania using state-of-the-art genomic technologies while aiming to discover features allowing to track superparasites. The scientists have found a series of mutations that were specific for these drug resistant and more virulent microbes and developed an easy-to-apply assay that would allow to detect them rapidly. The results appear in the current issue of the Journal of Infectious Diseases.
“Thanks to the discovery of these mutations, made possible through funding by the European Commission, the spread and emergence of these drug resistant parasites can be more efficiently monitored, contributing to a better and more adequate control of the parasite and the disease it causes,” said lead author Dr Manu Vanaerschot of the Institute of Tropical Medicine in Antwerpen, Belgium.
“We hope that this finding will ultimately pave the way to a field applicable drug resistance detection device not only for pentavalent antimonials but for all antileishmanial drugs. This is an important breakthrough which will help immensely in the control of the menace of leishmaniasis”, added study co-author Dr Shyam Sundar of the Banaras Hindu University.
Technological revolutions during the last years have allowed a huge effort of sequencing the genome of hundreds of microbes. This type of research provides an unprecedented potential for new solutions to fight these pathogens by revealing their Achilles heal, so to say. These technologies can reveal the microbes true identity, offering new targets for drugs or vaccines and allowing scientists to track them.
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Bibliographic information: Vanaerschot et al. 2012. Genetic markers for SSG-resistance in Leishmania donovani and SSG-treatment failure in visceral leishmaniasis patients of the Indian subcontinent. Journal of Infectious Diseases, Jun 29, ahead of print; doi: 10.1093/infdis/jis424
