ABSTRACT
Infections by protozoa can cause some of the most serious human diseases, particularly in tropical regions. However, the number of available drugs used to treat such diseases tends to be limited with relatively high toxicity, and the vast majority of such drugs were developed in the 1920s to 1970s. The development of antiprotozoal drugs has been hindered owing in part to: (1) the highly complicated life cycles of such organisms and their ability to avoid innate immune defences;(2) challenges associated with culturing such organisms particularly in different phases of their growth and amplification;and (3) a lack of investment in biomedical research aimed at developing treatments for tropical diseases that do not tend to affect more affluent countries. Indeed, only three new drugs have entered into clinical trials in recent times, highlighting the tremendous gap in knowledge that should be bridged to more effectively treat protozoal infections.