Protozoa represent a diverse group of unicellular eukaryotic organisms that are free-living or parasitic and can cause significant disease beyond the gastrointestinal tract. Protozoa possess complex life cycles and transmission routes that can lead to a variety of clinical manifestations, affecting organs such as the liver, lungs, and central nervous system. Many protozoa also affect the skin and subcutaneous tissues. Extraintestinal protozoa infections include the following:
(See also Overview of Free-Living Amebas.)
Some pathogenic protozoa are introduced into humans by vectors such as Anopheles mosquitoes, Triatominae bugs, and tsetse flies. Understanding the epidemiologic risk factors, life cycles, and resulting pathophysiology of extraintestinal protozoa is therefore critical for diagnosis and management, especially in immunocompromised patients, who may be at increased risk.
See Approach to Parasitic Infections for additional information regarding diagnosis, treatment, and prevention of these infections.
