Visceral leishmaniasis (VL), also known as kala-azar, is caused by the protozoan parasites Leishmania donovani and Leishmania infantum (= Leishmania chagasi), and is a potentially fatal disease with a worldwide distribution in Asia, East Africa, South America and the Mediterranean region (including Southern Europe). Almost all VL patients die within months if untreated. Leishmaniasis persists in poor and remote areas, where there is limited health care and patients have little access to preventive measures and affordable drugs. For VL, almost all of the 500,000 new cases arising from recurrent epidemics each year occur in the rural areas of the Indian subcontinent ( India, Nepal, Bangladesh), Brazil, Sudan and Ethiopia. The real burden of VL is unknown, but it is estimated that only 20% of cases are reported in India.The parasites are transmitted through the bite of female phlebotomine sand flies and in the human host are obligate intracellular parasites of the mononuclear phagocyte system, surviving and multiplying in different macrophage subsets in many different tissues. Sub-clinical infection in partially immune humans may be an important source of parasites when sand flies are active. Other mammals, often canids, either domesticated or wild, act as an additional zoonotic reservoir of Leishmania infantum. Patients with VL develop splenomegaly, irregular febrile episodes, anaemia, pancytopaenia, weight loss and weakness progressively over a period of weeks or even months.
The incidence of leishmaniasis shows an important increase over the last decades due (i) to failing preventive and therapeutic measures in developing countries as a result of insufficient/inefficient control of vector and reservoir, and emergence of drug resistant parasites, (ii) to urbanization and climate changes that expose naïve populations to infected Sand flies in previously unaffected areas, and (iii) to Leishmania -HIV co-infections and anthroponotic transmission by needle sharing in the industr ialized world. In consequence, leishmaniasis has been declared by the World Health Organisation (WHO) as a category I neglected disease for which no vaccine and no efficient, safe, and affordable treatment is available. The need to search for more effective medicine to treat leishmaniasis was highlighted by the WHO during the 60 th World Health Assembly in March 2007. The 193 Member States recognised leishmaniasis as one of the most neglected tropical diseases and approved a resolution on the control of this disease. Member States were urged to find alternative safe, effective and affordable medicines to treat VL.