Blood protozoan parasites are single-cell organisms that can be found in the
bloodstream of the infected individuals or spread to others through exposure to
infected blood as in blood transfusion. The medically important blood protozoa
are Plasmodium spp., Leishmania spp., and Trypanosoma spp. Infection by these
parasites is naturally transmitted by insects (vectors). They cause life-threatening
diseases that are among the most widespread and lethal all over the world with
high prevalence in developing countries. Research studies showed that extracellular
vesicles (EVs) released from these blood protozoa or infected host cells play
a significant role in the pathogenesis of parasitic diseases and have an effective
role on the host immune responses. Blood protozoa–released EVs transfer genetic
materials among parasites and different cells in the host leading to the dissemination
of parasitic infections. More importantly, EVs provide a new direction in the
management of blood protozoan parasitic diseases as well as may be candidates
for immune prevention of these parasitic diseases. This chapter summarizes the
implications of extracellular vesicles in blood protozoan parasitic diseases,
mainly focusing on trypanosomiasis, leishmaniasis, and malaria.