Cyclospora

Cyclosporan organisms were first described by Eimer in 1870, and the genus Cyclosporn was named by Schneider in 1881.(30,40) Subsequently, oocysts ranging in size from 12 to 36 by 6 to 22 mu m and designated as members of various Cyclospora species have been detected in the intestines of snakes, myriapods, and rodents.(40) Ashford provided the first description of human-associated cyclosporan oocysts, based on detection in stool specimens collected in 1977 and 1978, from three individuals living in Papua New Guinea. Two of them had reported diarrhea.(2,3) The unfamiliar and nonspecific features of these oocysts hampered classification. Ashford's speculation that the organisms might be detected in other parts of the world ultimately proved to be correct; however, this realization followed a tortuous course over the next 15 years. Beginning in the mid-1980s, Cyclospora oocysts found in human diarrheal stool specimens were given a variety of identifiers, including fungal spores, cyanobacterium-like bodies, blue-green algae, and large Cryptosporidium.* In retrospect, all of the descriptions corresponded to that of a human-associated Cyclospora. Confirmation of genus assignment occurred in 1993 when Ortega et al succeeded in inducing sporulation and demonstrating that the organism contained two sporocysts per oocyst and two sporozoites per sporocyst.(41) The first known outbreak of human cyclosporiasis in the United States took place in 1990 in a hospital dormitory in Chicago.(28) Otherwise, only sporadic cases, mostly in travelers, and two small clusters of infection were recognized in North America before 1996.(6, 29) In the spring and summer of 1996, 1465 sporadic and cluster-associated cases of cyclosporiasis were reported in the United States and Canada.(24) Over 1000 cases again have been reported during the spring and early summer of 1997.(7, 8) The escalating number of cases over the past 2 years, attributed to consumption of contaminated food, have sparked a national effort coordinated by the Centers for Disease Control and Prevention to unravel the mysteries of this enigmatic, emerging coccidian pathogen.(14, 42)