Importance of nonenteric protozoan infections in immunocompromised people

Abstract

There are many neglected nonenteric protozoa able to cause serious morbidity and mortality in humans, particularly in the developing world. Diseases caused by certain protozoa are often more severe in the presence of HIV. While information regarding neglected tropical diseases caused by trypanosomatids and Plasmodium is abundant, these protozoa are often not a first consideration in Western countries where they are not endemic. As such, diagnostics may not be available in these regions. Due to global travel and immigration, this has become an increasing problem. Inversely, in certain parts of the world (particularly sub-Saharan Africa), the HIV problem is so severe that diseases like microsporidiosis and toxoplasmosis are common. In Western countries, due to the availability of highly active antiretroviral therapy (HAART), these diseases are infrequently encountered. While free-living amoebae are rarely encountered in a clinical setting, when infections do occur, they are often fatal. Rapid diagnosis and treatment are essential to the survival of patients infected with these organisms. This paper reviews information on the diagnosis and treatment of nonenteric protozoal diseases in immunocompromised people, with a focus on patients infected with HIV. The nonenteric microsporidia, some trypanosomatids, Toxoplasma spp., Neospora spp., some free-living amoebae, Plasmodium spp., and Babesia spp. are discussed.

FIG. 1.

Transmission electron micrograph of an Encephalitozoon cuniculi spore. The main characteristics are labeled, including the polar filament (PF), posterior vacuole (PV), plasma membrane (PM), endospore (EN), exospore (EX), polarplast (Pp), and nucleus (Nu).

FIG. 2.

Clinical presentation of cutaneous leishmaniasis. (A) Ulcerative lesion of the face resulting in complete perforation of the cheek. (B) Partially healed cutaneous lesion of the hand.

FIG. 3.

Diffuse cutaneous leishmaniasis presenting as widespread, nonulcerative plaques.

FIG. 4.

Microscopic images from clinical samples. (A) Trypanosoma brucei trypomastigotes in a blood smear (Leishman stain). (B) Oval-shaped Leishmania infantum amastigotes from a bone marrow aspirate (Leishman stain). (C) Toxoplasma gondii tachyzoites from CSF (Giemsa stain). (D) Typical round Leishmania amastigotes from a bone marrow aspirate (Leishman stain).

FIG. 5.

Clinical presentation of Acanthamoeba keratitis. (Courtesy of Paul Badenoch.) (A) Keratitis demonstrating ring-stage infiltrate. (B) Keratitis with multiple ring infiltrates and hypopyon. (C) Keratitis with near-total suppuration.

FIG. 6.

Fixed, stained sections from corneal scrapings showing cysts and a trophozoite of Acanthamoeba. (Courtesy of Paul Badenoch.) (A) Acanthamoeba cysts stained with calcofluor white. (B) Acanthamoeba cyst stained with a Giemsa stain. (C) Acanthamoeba cyst stained with a Gram stain. (D) Acanthamoeba trophozoite stained with a Giemsa stain.