History[ edit ] The first published report of Cyclospora cayetanensis in humans appears to be by Ashford , who found unidentified Isospora -like coccidia in the feces of three individuals in Papua, New Guinea. The photomicrographs in the paper reveal an organism morphologically identical to that seen now. Later, Narango et al. 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", or CLB. Eventually, Ortega et al.
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Resources Causal Agents Cyclospora cayetanensis is a coccidian protozoan. It appears that all human cases are caused by this species; no animal reservoirs for C. Life Cycle View Larger When freshly passed in stools, the oocyst is not infective thus, direct fecal-oral transmission cannot occur; this differentiates Cyclospora from another important coccidian parasite, Cryptosporidium.
The sporulated oocysts can contaminate fresh produce and water which are then ingested. The oocysts excyst in the gastrointestinal tract, freeing the sporozoites, which invade the epithelial cells of the small intestine.
Inside the cells they undergo asexual multiplication into type I and type II meronts. Merozoites from type I meronts likely remain in the asexual cycle, while merozoites from type II meronts undergo sexual development into macrogametocytes and microgametocytes upon invasion of another host cell.
Fertilization occurs, and the zygote develops to an oocyst which is released from the host cell and shed in the stool. Several aspects of intracellular replication and development are still unknown, and the potential mechanisms of contamination of food and water are still under investigation.
Hosts Humans appear to be the only major host for C. Occasionally, cysts are recovered from animal feces, but it is likely that this represents spurious passage following coprophagy. Geographic Distribution Cyclosporiasis has been reported in many countries, but is most common in tropical and subtropical areas. In the United States, the majority of cases are reported during the spring and summer months. Outbreaks have been identified nearly every year since the mids. Clinical Presentation After an average incubation period of one week, symptomatic infections typically manifest as watery diarrhea of varying severity.
Other manifestations include complications of dysentery, further abdominal symptoms, and sometimes non-specific systemic symptoms e. Untreated infections typically last for 10—12 weeks and may follow a relapsing course.
The duration of symptoms and associated weight loss are greater in individuals with HIV or possibly other immunosuppressive conditions. Infections can be asymptomatic in disease-endemic regions. Cyclospora cayetanensis oocysts in wet mounts. Cyclospora cayetanensis oocysts are spherical, 7. Sporulation in the environment is temperature-dependent and may take one to several weeks for an infective oocyst to contain two sporocysts, each containing two sporozoites.
Oocysts of C. Figure A: Oocyst of C. Figure B: Oocyst of C. Figure C: Oocyst of C. Image taken at x magnification. Figure D: Oocyst of C. Figure B: Oocysts of C. Figure E: Oocyst of C. Figure F: Oocyst of C. Figure A: Oocysts of C. Note the variability of staining in the four oocysts. Figure B: Two oocysts of C. Both oocysts failed to take up the carbol fuschin stain.
Figure C: Oocysts of C. Note the wrinkled edge and the lack of stain in the two oocysts. Figure E: Oocysts of C. Figure F: Oocysts of C. Figure E: A pair of oocysts of C. Cryptosporidium spp. The refractile globules are easily visible under DIC. There are two sporocysts are visible in this image. Figure F: Rupturing oocyst of C. One sporocyst has has been released from the mature oocyst; the second sporocyst is still contained within the oocyst wall.
Laboratory Diagnosis Unpreserved stool collected in enteric transport media e. Unpreserved specimens should be refrigerated and sent to the diagnostic laboratory as rapidly as possible. Cyclospora oocysts can be excreted intermittently and in small numbers. Concentration procedures should be used to maximize recovery of oocysts. Both modified acid-fast stains and modified safranin staining will stain Cyclospora cysts from a pink to brilliant red.
Staining may be more variable using modified acid-fast. Other common stains including Giemsa and trichrome are not adequate for the reliable detection of Cyclospora. Molecular Diagnosis Several conventional and real-time PCR protocols have been developed to specifically detect Cyclospora cayetanensis in stool.
Commercial, FDA-approved panels that include other enteric pathogens are available and are highly sensitive. Laboratory Safety Standard precautions for the processing of stool samples apply. Cyclospora oocysts are not immediately infectious when passed, however, precautions should still be taken to avoid exposure to other pathogens that may be present in stools.
Update on Cyclospora cayetanensis, a food-borne and waterborne parasite. Clinical Microbiology Reviews, 23 1 , pp. Casillas, S. Morbidity and Mortality Weekly Report, 67 39 , p.
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Parásitos - Ciclosporosis (infección por Cyclospora)