Overview Of Protozoal Infections And Antiprotozals

Protozoa ( Table 1) are microscopic unicellular eukaryotes found in most habitats worldwide.  They were first visualized in 1674 by Antonie van Leeuwenhoek using a single-lens microscope.  Protozoal infection can be commensal or pathogenic depending on the organism, the immune status of the host, and the prevalence of the protozoal organism within a region.  Protozoa often have complex lifecycles that include alterations in pathogen structure or host environment during different stages.  Treatment must be tailored to local resistance patterns and may require a species-specific medication.

Pathogenic protozoa are typically transmitted by the fecal-oral route or by insect bite (eg, mosquitos, ticks, bugs) ( Table 2).  In humans, protozoal disease most commonly occurs in the intestines, bloodstream, or genitourinary tract; however, immunocompromised hosts are at risk for a wider array of illnesses by various protozoa, some of which may attack other organs (eg, lungs, brain).  A broad discussion of common protozoal illnesses in different organ systems follows.