ABSTRACT
I. BACKGROUND Cyclospora cayetanensis is a protozoan parasite of humans that causes diarrheal illness after colonizing the mucosal epithelium of the small intestine. In retrospect, this coccidian parasite was first described in persons from Papua New Guinea in 1979 (1), but the specific identification as a Cyclospora species would not occur until 1993 (2). In the intervening years the parasite was alternately described as either a large variant of Cryptosporidium, a blue-green alga (cyanobacteriumlike), or an unidentified coccidian. The actual nature was not discerned until stool specimens were stored without a fixative for sufficient time to allow the undifferentiated oocysts to sporulate and reveal both sporocysts and sporozoites (2,3).
