Cyclosporiasis pathophysiology
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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
Cyclospora cayetanensis infects epithelial cells of the gastrointestinal tract, especially those of the duodenum and jejunum. It is transmitted through the fecal-oral route. C. cayetanensis is excreted in stool in its noninfectious form, and requires certain environmental conditions, such as temperatures of 23-32ºC, to sporulate and become infectious. Once ingested, from contaminated water and/or food, sporozoites are released from oocysts, and infect gastrointestinal cells. It causes histological changes in the infected mucosa, which may include: loss of the brush border appearance, villous atrophy, crypt hyperplasia, and vacuolization of the tips of the villi.
Pathogenesis
Life Cycle
Unsporulated oocysts of Cyclospora cayetanensis are excreted from infected individuals. When freshly passed in stool, the oocyst is not infective (thus, direct fecal-oral transmission cannot occur, which differentiates Cyclospora from other important coccidian parasites such as Cryptosporidium). Under adequate temperatures (23-32ºC), oocysts take about 7-15 days to sporulate and become infectious. After ingestion, oocysts excyst to release elongated sporozoites. Sporozoites then infect epithelial cells of the gastrointestinal tract, particularly those of the duodenum and jejunum. The sporozoites undergo asexual reproduction giving rise to meronts type I and II, which then differentiate into gametocytes. Gametocytes are fertilized to produce a zygote.[1][2] Inside cells, zygotes undergo asexual reproduction and development to mature into oocysts, which are shed in the stool.[3] C. cayetanensis oocysts have also been isolated from non-gastrointestinal sites, such as sputum, especially in immunocompromised patients with HIV and concomitant TB. This led to the hypothesis that C. cayetanensis may be an opportunistic pathogen.[4]
Transmission
C. cayetanensis is transmitted by the fecal-oral route. Individuals are infected with Cyclospora by ingesting sporulated oocysts (infective form of the parasite). This occurs most commonly when food or water contaminated with human fecal material is consumed. The parasite is shed in the feces of infected persons in the unsporulated oocyst form (non-infective) and, in a favorable environment, sporulate and become infective. Therefore, direct person-to-person transmission is unlikely, as is transmission via ingestion of newly contaminated food or water.[3][2]
Pathology
C. cayetanensis infects epithelial cells of the small intestine, especially those of the jejunum. Infected patients may have evidence of intestinal injury on endoscopy such as mucosal erythema.[2] Histologic samples of small bowel of these patients demonstrate involvement of the lamina propria and neutrophilic infiltration in some cases. Cyclosporiasis may demonstrates evidence of chronic inflammation, with plasma cells observed in mucosal samples of infected patients.[5] Classically, immunocompromised patients are more prone to develop chronic inflammation of the gastrointestinal epithelium.[2]
Infected epithelial cells of the gastrointestinal tissue may demonstrate the following changes:[5][2]
- Loss of brush border appearance
- Vacuolization of the tips of the villi
- Epithelial changes from columnar to cuboid
- Villous atrophy (partial)
- Crypt hyperplasia
- Absence of parasitic vacuoles in biopsied samples
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.
- ↑ 2.0 2.1 2.2 2.3 2.4 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.
- ↑ 3.0 3.1 3.2 "Cyclosporiasis".
- ↑ 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.
- ↑ 5.0 5.1 Connor BA, Shlim DR, Scholes JV, Rayburn JL, Reidy J, Rajah R (1993). "Pathologic changes in the small bowel in nine patients with diarrhea associated with a coccidia-like body". Ann Intern Med. 119 (5): 377–82. PMID 8338291.