Leishmaniasis control: limitations of current drugs and prospects of natural products

Abstract Leishmaniases are endemic in 98 countries and a serious threat to approximately 310 million people living in endemic regions of affected countries. Out of 53 described species of Leishmania parasites, 20 are known to cause human pathogenesis and may produce three discreet clinical manifestations, that is, cutaneous (CL), mucocutaneous (MCL), and visceral (VL) leishmaniasis that differ in their immunopathologies and degree of morbidity and mortality. It is estimated that approximately 0.7–1.2 million new CL and 0.2–0.4 million of new VL cases occur each year in disease endemic countries. The current treatment options comprise only three drugs, viz. pentavalent antimonials, amphotericin B (and its liposomal formulation, AmBisome), and miltefosine that also produce severe side effects. These drugs do not produce a sterile cure, leaving behind a possible and potent source of parasitic reservoirs for further disease transmission along with the emergence of drug-resistant parasites. The limited drug regimen, coupled with the unavailability of a licensed vaccine, necessitates the development of a true antileishmanial drug to combat increasing incidences of leishmaniasis. In this chapter, we summarize a wide range of compounds isolated from various natural sources that are worth screening to develop a true antileishmanial drug along with a short discussion on the limitations of current drugs.