**Abstract**

Extracellular vesicles (EVs) have lately emerged as crucial mediators in parasite infections. Recent research suggests that protozoan parasites, including *Leishmania*, employ EVs as transport vehicles to deliver biologically active effector molecules such as parasitic virulence factors to modulate the host immune system and their microenvironment. The immunomodulatory effects of EVs play an essential role in the formation and progression of parasitic diseases. The immunomodulatory strategies applied by EVs of protozoan origin have similarities to the development and progression of other infections or diseases such as cancer. In this chapter, we will provide recent insights into the role of EVs in host-pathogen interactions, intercellularcommunication, immunomodulation and pathogenesis of *Leishmania* and other protozoan parasites, including *Plasmodium spp., Toxoplasma spp*. and *Trypanosoma spp.* In addition, biologically inspired by the immunomodulation strategies of protozoan parasites, new immunotherapeutic models are being currently investigated to implement EVs more intensively in both therapy and diagnostics. Therefore, besides highlighting the role of EVs in protozoan infections, this chapter sheds light briefly on new immunotherapeutic approaches utilizing the strategies of protozoan EVs in medicine.

**Keywords:** extracellular vesicles, immunomodulation, pathogenesis, protozoan, *Leishmania*, infectious disease
