domingo, 18 de agosto de 2013

DPDx - Cyclosporiasis

DPDx - Cyclosporiasis

Parasites and Health [Last Modified: 07/20/2009 11:14:59]
[Cyclospora cayetanensis]

Causal Agent:
The causal agent has been only recently identified as a unicellular coccidian parasite.  The species designation Cyclospora cayetanensis was given in 1994 to Peruvian isolates of human-associated Cyclospora.  It appears that all human cases are caused by this species.
  1. Herwaldt BL. Cyclospora cayetanensis: a review, focusing on the outbreaks of cyclosporiasis in the 1990s.  Clin Infect Dis 2000;31:1040-1057.
  2. Ortega YR, Gilman RH, Sterling CR. A new coccidian parasite (Apicomplexa: Eimeriidae) from humans. J Parasitol 1994;80:625-629.
  3. Pieniazek NJ, Herwaldt BL. Reevaluating the molecular taxonomy: Is human-associated Cyclospora a mammalian Eimeria species? Emerg Infect Dis 1997;3:381-383.
Life Cycle:
Life cycle of Cyclospora cayetanensis
Some of elements of this figure were created based on an illustration by Ortega et al. Cyclospora cayetanensis. In: Advances in Parasitology: opportunistic protozoa in humans. San Diego: Academic Press; 1998. p. 399-418.
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  .  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  .  Inside the cells they undergo asexual multiplication and sexual development to mature into oocysts, which will be shed in stools  .  The potential mechanisms of contamination of food and water are still under investigation.
Geographic Distribution:
Cyclosporiasis has been reported in many countries, but is most common in tropical and subtropical areas.  Since 1990, at least 11 foodborne outbreaks of cyclosporiasis, affecting approximately 3600 persons, have been documented in the United States and Canada.

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