Cyclosporiasis pathophysiology: Difference between revisions
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===Life Cycle=== | ===Life Cycle=== | ||
Unsporulated oocysts of ''Cyclospora cayetanensis'' are excreted from infected persons. Under adequate temperatures (23-27ºC), these take about 7-15 days to sporulate, in order to become infectious. After being ingested, from contaminated water and food, oocysts excyst to release the sporozoites. Sporozoites will then infect epithelial cells of the gastrointestinal tract, particularly those of the duodenum and jejunum. The sporozoites undergo asexual reproduction, originating meronts type I and II, which will then differentiate into gametocytes. These last will be fertilized to produce a zygote. Oocysts are formed from the zygote, and then excreted as oocysts into the environment.<ref name="pmid10864257">{{cite journal| author=Eberhard ML, Ortega YR, Hanes DE, Nace EK, Do RQ, Robl MG et al.| title=Attempts to establish experimental Cyclospora cayetanensis infection in laboratory animals. | journal=J Parasitol | year= 2000 | volume= 86 | issue= 3 | pages= 577-82 | pmid=10864257 | doi=10.1645/0022-3395(2000)086[0577:ATEECC]2.0.CO;2 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10864257 }} </ref><ref name="pmid20065331">{{cite journal| author=Ortega YR, Sanchez R| title=Update on Cyclospora cayetanensis, a food-borne and waterborne parasite. | journal=Clin Microbiol Rev | year= 2010 | volume= 23 | issue= 1 | pages= 218-34 | pmid=20065331 | doi=10.1128/CMR.00026-09 | pmc=PMC2806662 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20065331 }} </ref> | Unsporulated oocysts of ''Cyclospora cayetanensis'' are excreted from infected persons. Under adequate temperatures (23-27ºC), these take about 7-15 days to sporulate, in order to become infectious. After being ingested, from contaminated water and food, oocysts excyst to release the sporozoites. Sporozoites will then infect epithelial cells of the gastrointestinal tract, particularly those of the duodenum and jejunum. The sporozoites undergo asexual reproduction, originating meronts type I and II, which will then differentiate into gametocytes. These last will be fertilized to produce a zygote. Oocysts are formed from the zygote, and then excreted as oocysts into the environment.<ref name="pmid10864257">{{cite journal| author=Eberhard ML, Ortega YR, Hanes DE, Nace EK, Do RQ, Robl MG et al.| title=Attempts to establish experimental Cyclospora cayetanensis infection in laboratory animals. | journal=J Parasitol | year= 2000 | volume= 86 | issue= 3 | pages= 577-82 | pmid=10864257 | doi=10.1645/0022-3395(2000)086[0577:ATEECC]2.0.CO;2 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10864257 }} </ref><ref name="pmid20065331">{{cite journal| author=Ortega YR, Sanchez R| title=Update on Cyclospora cayetanensis, a food-borne and waterborne parasite. | journal=Clin Microbiol Rev | year= 2010 | volume= 23 | issue= 1 | pages= 218-34 | pmid=20065331 | doi=10.1128/CMR.00026-09 | pmc=PMC2806662 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20065331 }} </ref> | ||
''C. cayetanensis'' oocysts have also been isolated from non gastrointestinal sites, namely from sputum of immunocompromised patients with HIV and concomitant TB. This leads to hypothesis that ''C. cayetanensis'' may be an opportunistic pathogen.<ref name="pmid10810327">{{cite journal| author=Di Gliullo AB, Cribari MS, Bava AJ, Cicconetti JS, Collazos R| title=Cyclospora cayetanensis in sputum and stool samples. | journal=Rev Inst Med Trop Sao Paulo | year= 2000 | volume= 42 | issue= 2 | pages= 115-7 | pmid=10810327 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10810327 }} </ref> | |||
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Insects, rotifers, and free-living nematodes could also play a role in the dissemination of oocysts, a phenomenon that has been described for Cryptosporidium (67, 74, 75, 90, 179) and other food-borne pathogens. The nematode Caenorhabditis elegans can ingest and excrete infectious bacteria (23, 98, 99) as well as Cryptosporidium parvum oocysts. Although the oocysts of Cyclospora are larger and may not be ingested by C. elegans, other, larger species of free-living nematodes could have a significant role in Cyclospora oocyst dissemination. Therefore, the role of free-living nematodes and other mechanical vectors in the contamination of produce and other food crops needs to be examined further (90). | Insects, rotifers, and free-living nematodes could also play a role in the dissemination of oocysts, a phenomenon that has been described for Cryptosporidium (67, 74, 75, 90, 179) and other food-borne pathogens. The nematode Caenorhabditis elegans can ingest and excrete infectious bacteria (23, 98, 99) as well as Cryptosporidium parvum oocysts. Although the oocysts of Cyclospora are larger and may not be ingested by C. elegans, other, larger species of free-living nematodes could have a significant role in Cyclospora oocyst dissemination. Therefore, the role of free-living nematodes and other mechanical vectors in the contamination of produce and other food crops needs to be examined further (90). | ||
Travel to rural areas and ingestion of contami- nated foods could be modes of infection. Accidental inhalation of oocysts has also been suggested (93) | |||
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Revision as of 18:15, 18 September 2014
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
Overview
Fresh produce and water can serve as vehicles for transmission and the sporulated oocysts are ingested (in contaminated food or water). The oocysts excyst in the gastrointestinal tract, freeing the sporozoites which invade the epithelial cells of the small intestine.
Pathogenesis
Life Cycle
Unsporulated oocysts of Cyclospora cayetanensis are excreted from infected persons. Under adequate temperatures (23-27ºC), these take about 7-15 days to sporulate, in order to become infectious. After being ingested, from contaminated water and food, oocysts excyst to release the sporozoites. Sporozoites will then infect epithelial cells of the gastrointestinal tract, particularly those of the duodenum and jejunum. The sporozoites undergo asexual reproduction, originating meronts type I and II, which will then differentiate into gametocytes. These last will be fertilized to produce a zygote. Oocysts are formed from the zygote, and then excreted as oocysts into the environment.[1][2]
C. cayetanensis oocysts have also been isolated from non gastrointestinal sites, namely from sputum of immunocompromised patients with HIV and concomitant TB. This leads to hypothesis that C. cayetanensis may be an opportunistic pathogen.[3]
- 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).
- In the environment, sporulation occurs after days or weeks at temperatures between 22°C to 32°C, resulting in division of the sporont into two sporocysts, each containing two elongate sporozoites.
- 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 and sexual development to mature into oocysts, which will be shed in stools.[4]
Various chemicals in the host's gastrointestinal tract cause the oocysts to excyst and release sporozoites; generally, two are observed per oocyst. After these sporozoites invade the epithelial cells, they undergo merogony, a form of asexual reproduction that results in many daughter merozoites. These daughter cells may either infect new host cells and initiate yet another round of merogony, or they can take on a sexual track via gametogony: daughter merozoites become male macrogamonts — which form many microgametes — and female macrogamonts. After fertilization has occurred via male microgamete fusion with female macrogamont, the zygote matures into an oocyst and ruptures the host cell, from which point it is passed with the stool. The oocysts that are passed are not, however, immediately infectious. Sporulation can take anywhere from one to several weeks, meaning that person-to-person transmission is not a likely problem. This differentiates C. cayentanensis from Cryptosporidium parvum — a closely related organism that causes a similar disease — since C. parvum oocysts are immediately infectious upon release from the host.
Life Cycle
The protozoan lives out its lifecycle intracellularly within the host’s epithelial cells and gastrointestinal tract. Infection is transmitted through the oral-fecal route, and begins when a person ingests oocysts in fecally contaminated food or water. Various chemicals in the hosts gastrointestinal tract cause the oocysts to excyst and release sporozoites; generally, two are observed per oocyst. After these sporozoites invade the epithelial cells, they undergo merogony, a form of asexual reproduction that results in many daughter merozoites. These daughter cells may either infect new host cells and initiate yet another round of merogony, or they can take on a sexual track via gametogony: daughter merozoites become male macrogamonts — which form many microgametes — and female macrogamonts. After fertilization has occurred via male microgamete fusion with female macrogamont, the zygote matures into an oocyst and ruptures the host cell, from which point it is passed with the stool. The oocysts that are passed are not, however, immediately infectious. Sporulation can take anywhere from one to several weeks, meaning that person-to-person transmission is not a likely problem. This differentiates C. cayetanensis from Cryptosporidium parvum — a closely related organism that causes a similar disease — since C. parvum oocysts are immediately infectious upon release from the host.
Transmission
The protozoan lives out its lifecycle intracellularly within the host’s epithelial cells and gastrointestinal tract. Infection is transmitted through the oral-fecal route, and begins when a person ingests oocysts in fecally contaminated food or water.
- Fresh produce and water can serve as vehicles for transmission and the sporulated oocysts are ingested (in contaminated food or water).
Microscopic Pathology
References
- ↑ Eberhard ML, Ortega YR, Hanes DE, Nace EK, Do RQ, Robl MG; et al. (2000). "Attempts to establish experimental Cyclospora cayetanensis infection in laboratory animals". J Parasitol. 86 (3): 577–82. doi:10.1645/0022-3395(2000)086[0577:ATEECC]2.0.CO;2. PMID 10864257.
- ↑ Ortega YR, Sanchez R (2010). "Update on Cyclospora cayetanensis, a food-borne and waterborne parasite". Clin Microbiol Rev. 23 (1): 218–34. doi:10.1128/CMR.00026-09. PMC 2806662. PMID 20065331.
- ↑ Di Gliullo AB, Cribari MS, Bava AJ, Cicconetti JS, Collazos R (2000). "Cyclospora cayetanensis in sputum and stool samples". Rev Inst Med Trop Sao Paulo. 42 (2): 115–7. PMID 10810327.
- ↑ 4.0 4.1 "Cyclosporiasis".