Cyclospora cayetanensis

Synonym: Cryptosporidium cayetanensis Tauxe, 1997 lapsus
Synonym: Cyclospora cayetenensis Duluol, Teilhac, Poirot, Heyer, Beaugerie, & Chatelet, 1996 lapsus

Steve J. Upton Division of Biology, Kansas State University, Manhattan, KS 66506

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. If you want additional information on the life-cycle of a coccidian, try Andreas Weck-Heimann's Life-cycle Eimeria homepage.

Hosts: In addition to humans, C. cayetanensis has been reported from chimpanzees, Pan troglodytes from Uganda (Ashford et al., 1993), and baboons and chimpanzees from Tanzania (Smith et al., 1996). It is likely that this parasite will be found to infect a wide range of primates. There are also reports of the parasite in dogs (Yai et al. 1997) and poultry (Garcia-Lopez et al. 1996) but I am not yet convinced these cases represent true parasitism.

DiagnosisCyclospora are spherical, measure approximately 9.0 micrometers in diameter, and are passed in the feces unsporulated. They are passed in low to moderate numbers, and are easily recognized using conventional microscopy. Fluorescent microscopy employing a filter with a wavelength in the range of 340-380 nm reveals the oocysts to glow a bright, pale blue. Only a moron could misdiagnose the parasite using this latter method.

Clinical signs and pathogenesis: Individuals infected with Cyclospora may experience prolonged watery diarrhea, abdominal cramping, weight loss, anorexia, myalgia, and occasionally vomiting and/or fever. Symptoms generally begin approximately 1 week after ingestion of oocysts and may persist for a month or more. The small intestine becomes inflammed, and the parasite causes mucosal changes that include villous atropy and crypt hyperplasia. Mild infections may produce few or no clinical signs.

Epidemiology: With the exception of some outbreaks, the overall prevalence of Cyclospora in most populations appear to be far less than 1%. Outbreaks seem to occur most frequently in late spring and summer, and these warmer temperatures are clearly needed to get oocysts to sporulate with any rapidity. In addition, this time of year correlates with increased import of fruits and vegetables into the US from our more southern neighbors. Individuals become infected when they ingest contaminated food or water containing viable, sporulated oocysts. Because so many of the foods we consume are shipped over long distances and involve contact by many individuals, transportation of pathogens such as Cyclospora between states and countries has become unavoidable. However, the odds of becoming infected with Cyclospora, and many other foodborne pathogens, can be greatly diminished by simply washing fruits and vegetables well prior to consumption. However, it should be noted that simply washing foods does not removed 100% of the oocysts (see Ortega et al., 1997b).

Treatment: Some success has been achieved treating patients with co-trimoxazole (160 mg trimethoprim, 800 mg sulfamethoxazole) twice daily for 7 days. Children should receive trimethoprim at 5 mg/kg body weight plus sulfamethoxazole at 25 mg/kg body weight twice a day for 7 days. For more specific information on treatment, see the papers below marked with an asterisk (*).

Cyclospora cayetanensis: additional links

Case report (by D. Purych, MD)
CDC public announcement
Differentiation of Cyclospora from Eimeria by PCR
MedicineNet announcement
Outbreaks in 1996 (MMWR 45: 549-551, June 1996)
Protocol for preparation of oocysts for PCR following extraction from produce