Evolution of the protist Leishmania donovani, causative agent of serious human disease

 Lukeš J., Jirků M., Chocholová E., Oborník M., Horák A., Zemanová E.

Leishmaniasis is a geographically widespread disease of humans, whose incidence has been increasing. There are about 2 million people infected per year and over 350 million in 88 countries are nowadays at risk. The disease is caused by flagellated protist of the genus Leishmania (Kinetoplastida), which is transmitted to the human host from a phlebotom flies (Diptera: Phlebotominae). About 20 Leishmania species are pathogenic for humans. Leishmaniasis is a complex disease, including cutaneous and also visceral forms of the disease, the later of which is lethal if untreated. The Leishmania donovani complex has pathogenic members that have been classified to four distinct species, L. archibaldi, L. chagasi, L. donovani, L. infantum, based on their vectors, reservoir hosts and pathology. We performed a substantial taxonomy revision of the complex based on phylogenetic and population genetics analyses of over 18 000 characters from selected 25 representative strains. In addition, we have formulated new a hypothesis about the origin and spread of theL. donovani complex. Strong correlation between the genetics and phylogeny of strains and their geographical origin has been discovered. On the other hand, no relation has been found between the genetic clustering, pathology of the disease and its traditional classification. We propose a revised taxonomy distinguishing only two species within the complex, L. donovani in Africa and India, and L. infantum in Europe. Our evolutionary scenario supposes the appearance of the complex ancestor in Central America about 36-46 million years ago (MYA), diversification of the complex in Asia about 1.2 - 0.7 MYA and arrival to Europe and Africa about 0.6-0.4 and 0.5-0.3 MYA respectively. We can expect that due to proposed global climate changes leishmaniasis will spread to the European regions that have been restricted to the vectors due to low temperatures.