Infections by Intestinal Coccidia and Giardia duodenalis

Abstract

The coccidians Cryptosporidium spp, Cyclospora cayetanensis, and Cystoisospora belli and the flagellate Giardia duodenalis are pathogenic protozoa associated with gastrointestinal manifestations. Diagnosis relies heavily on microscopy, and although ova-and-parasite examinations can detect Giardia and Cystoisospora, Cryptosporidium and Cyclospora often require specific diagnostic requests. Approved non-microscopy methods are available for Giardia and Cryptosporidium, although negative results are frequently followed by microscopic assays. Polymerase chain reaction-based methods are not frequently used for diagnosis of Giardia and Cryptosporidium and have been used primarily for epidemiologic or outbreak investigations of Giardia and Cryptosporidium.

Keywords: Cryptosporidium; Cyclospora cayetanensis; Cystoisospora belli; Giardia duodenalis; Human enteric coccidian.

Fig. 1

Comparison of (A, D) Cryptosporidium spp, (B, E) Cyclospora cayetanensis, and (C, F) Cystoisospora belli stained with modified acid-fast and safranin stains, original magnification × 1000. (Public domain images, courtesy of DPDx, Centers for Disease Control and Prevention, Atlanta, USA).

Fig. 2

Cyclospora cayetanensis oocyst viewed under normal light (left) and ultraviolet light (right) in an unstained wet mount. (Original magnification × 1000). (Courtesy of DPDx, Centers for Disease Control and Prevention, Atlanta, USA).

Fig. 3

Trophozoite (left) and cyst (right) of Giardia duodenalis (trichrome, original magnification × 1000). (Courtesy of DPDx, Centers for Disease Control and Prevention, Atlanta, USA.)