Skip to Main Content


This chapter offers a brief survey of the protozoan and helminthic parasites of medical importance. A synopsis of each parasite is provided within tables that are organized by the organ system that is infected (eg, intestinal and blood/tissue protozoan infections and intestinal and blood/tissue helminthic infections). Key concepts are provided at the beginning of the protozoa and helminths sections to give the reader an overview of the paradigms in medical parasitology. Current updates to information provided in this chapter can be found at the Centers for Disease Control and Prevention (CDC) website


The parasites covered in this chapter are categorized into two major groups: parasitic protozoa and parasitic helminths.

Protozoa are unicellular eukaryotes that form an entire kingdom. Classifying protozoan parasites into taxonomic groups is an ongoing process, and their status is often in a state of flux. For this reason, this chapter separates the parasitic protozoa into four traditional groups based on their means of locomotion and mode of reproduction: flagellates, amebae, sporozoa, and ciliates. Table 46-1 lists several medically important protozoan parasites by the organ system they infect, the mode of infection, diagnosis, treatment, and geographic location.

TABLE 46-1Synopsis of Protozoan Infections by Organ System

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.