Cyclospora Cayatenensis

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  • Topic: Apicomplexa, Cyclospora cayetanensis, Cyclosporiasis
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Cyclospora cayetanensis
Synonym: Cryptosporidium cayetanensis Tauxe, 1997 lapsus Synonym: Cyclospora cayetenensis Duluol, Teilhac, Poirot, Heyer, Beaugerie, & Chatelet, 1996 lapsus Updated: 31 October 2001
E-mail: Steve J. Upton Division of Biology, Kansas State University, Manhattan, KS 66506 Main menu: Cryptosporidium homepage

History: The first published report of Cyclospora cayetanensis in humans appears to be by Ashford (1979), who found unidentified Isospora-like coccidia in the feces of 3 individuals in Papua, New Guinea. At least the photomicrographs in the paper reveal an organism morphologically identical to that we see now. Later, Narango et al. (1989) reported what may be the same organism from several Peruvians with chronic diarrhea and termed the organism Cryptosporidium muris-like. Other investigators thought the unsporulated oocysts appeared more similar to cyanobacteria, and the name "cyanobacterium-like body" or CLB became prevalent in the literature (occasionally, authors also used the term "coccidian-like body" for CLB). Eventually, Ortega et al. (1992) published an abstract reporting that they had sporulated and excysted the oocysts, resulting in placement of the parasite in the genus Cyclospora. They also created the name Cyclospora cayetanensis at this time. However, since no morphologic information was presented in the abstract, C. cayetanensis technically became a nomen nudum (a named species without a description). Although Ortega et al. (1993) later published additional details about this coccidian, it wasn't until 1994 that a complete morphologic description was published to validate the name (Ortega et al., 1994). Thus, the correct name for this parasite is Cyclospora cayetanensis Ortega, Gilman, & Sterling, 1994, and the etymology of the nomen triviale is derived from Cayetano Heredia University in Lima, Peru. During this 2-year period when C. cayetanensis was a nomen nudum, anyone wishing to publish a complete morphologic description and change the name would have been free to do so. But, we are now doomed forever in our struggle to spell and pronounce "cayetanensis." Life-cycle and basic biology: The life-cycle of Cyclospora cayetanensis begins, like all enteric coccidia, with ingestion of a sporulated "oocyst" (the environmentally resistent cyst stage). This sporulated oocyst contains 2 "sporocysts" (smaller cysts within the oocyst), each enclosing 2 "sporozoites" (the infective stages; each oocyst contains a total of 4 sporozoites). Once inside the gut, these sporozoites exit from the sporocysts and oocyst, eventually penetrating epithelial cells along the small intestine. The preferred site is the jejunum. Sporozoites undergo multiple fission inside cells to form "meronts," which contain numerous "merozoites." Ortega et al. (1997a) has described two asexual generations: the first having 8-12 merozoites and the second as having 4 merozoites. The final generation of merozoites penetrate new cells to form gametes, which can also be found in the jejunum. Most gametes simply enlarge to form the female gamete, or "macrogamete." Some become "microgametocytes," which undergo multiple fission to form numerous flagellated sperm-like "microgametes." Mature microgametes exit the microgametocyte, fertilize the macrogametes, and a resistent oocyst wall is layed down around the zygote. In time, the unsporulated oocyst is sloughed from the intestinal wall along with the host cell and passes into the external environment with the feces. Further development of sporocysts and sporozoites is termed "sporogony" or "sporulation" and occurs only in the presence of the higher atmospheric oxygen concentrations. Sporulation is complete in 7-12 days at a "warm" room temperature, for instance at 30 C. Hosts: Humans may be the only true hosts for this coccidian. Although the parasite has been reported from chimpanzees, Pan troglodytes from Uganda (Ashford et al., 1993), and baboons and chimpanzees from Tanzania...
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