Cyclospora: An Overview

Popularization of the acid-fast stain in the early 1980s for detecting species in stool specimens set the stage for recognition of Cyclospora species. Between 1986 and 1993, there were nine reports linking diarrheal illness in more than 200 immunocompetent and immunocompromised children and adults to an unidentified, acid-fast organism resembling a Cryptosporidium [2-10]. On the basis of electron microscopic studies in 1990 that revealed photosynthesizing organelles within the organism, similar to those of blue-green algae, Long et al. suggested that it was a cyanobacterium similar to Chlorella species [7]. Thus, in addition to being called a large Cryptosporidium, the organism has been called a coccidian-like body or a cyanobacterium-like body (CLB), a bluegreen alga, a muris-like cyst, a fungal spore, and a species of Blastocystis. In 1993, Ortega et al. [11] succeeded in inducing Cyclospora to sporulate and showed that, when mature, it has two sporocysts, each containing two sporozoites. Thus, the organism is the oocyst stage of the coccidian parasite Cyclospora [11]. Detailed electron microscopic studies, which revealed that the Cyclospora sporozoites possess a membrane-bound nucleus and micronemes that are characteristic of the phylum Apicomplexa, provided additional evidence that the organism is a coccidian [11]. With use of molecular phylogenetic analysis, Relman [12] recently confirmed that Cyclospora is a coccidian related to Eimeria species and possibly most closely related to Isospora species [12]. It is of interest that the first report of human cyclospora infection (which had largely gone unnoticed until 1993) came from Papua New Guinea in 1979, before the popularization of acid-fast stained stool smears and the advent of molecular phylogenetic analysis [2, 13]. In that report, Ashford [2] detailed the morphological characteristics of a coccidian-like or-