Cyclospora cayetanensis

# Overview
Cyclospora cayetanensis is a protozoan that causes disease in humans, and possibly in other primates.  It has also been isolated from the feces of other animals such as ducks and chickens.  Due to the spherical shape of C. cayetanensis sporocytes, it was placed in the Cyclospora genus.  It has a double layered wall that gives it resistance against disinfectants and adhesins which are responsible for its adherence characteristics.  The bacteria show tropism for epithelial cells of the small intestine, especially of the duodenum and jejunum.

# Taxonomy
Eukaryota; Alveolata; Apicomplexa; Conoidasida; Coccidia; Eucoccidiorida; Eimeriorina; Eimeriidae; Cyclospora

# Biology
Cyclospora cayetanensis is an obligate intracellular apicomplexan, cyst-forming coccidian protozoan, of the family of Eimeriidae, which commonly causes self-limiting diarrhea.  Morphologically C. cayetanensis has spherical oocysts that are between 7.5 and 10 micrometers in diameter that also have a 50 nanometer thick bilayered wall with an outer threadlike coat that has been called a wrinkle by some researchers.
According to a phylogenetic analysis performed with the 18S rRNA gene, in the Cyclospora species isolated from a group of baboons, this species, although different, was proved to be similar to the C. cayetanensis that infects humans.  These two species were then documented was belonging to the same clade of the Eimeria species.  Other three species of Cyclospora were also identified in non-human primates and characterized with the SSU rRNA analysis, later that year.  Because there are morphologically similar, there can not be differentiated by light microscopy.  These species: C. cercopitheci, C. colobi and C. papionis were identified in green monkeys, colobus monkeys, and baboons, respectively.  C. cayetanensis and these three other species of Cyclospora all share the characteristic of being host-specific.
It is not known the exact conditions and location required for the sporulation of oocysts in the natural environment, however, these data would help to understand and predict the distribution and seasonality of C. cayetanensis.  Due to its double-layered wall it is highly resistant, particularly to disinfectants used during food processing. This resistance along with its binding affinity to certain produce, explains the risks associated with contaminated foods.  The adhesive properties of C. cayetanensis are stronger than those of the oocysts of Giardia or Cryptosporidium, however, the responsible adhesins are yet to be identified.

# Tropism
Cyclospora cayetanensis shows tropism for epithelial cells of the small intestine, especially for the jejunum.

# Natural Reservoir
C. cayetanensis is an host specific parasite that is able to infect humans.  Cyclospora oocysts have also been isolated from the feces of several animals, such as ducks, chickens and dogs.  Attempts to identify and to infect different animals with C. cayetanensis have failed.
Certain shellfish may acquire C. cayetanensis from contaminated waters, and concentrate its oocyst for several days.

# Differential diagnosis
Cyclospora cayetanensis infection must be differentiated from other causes of viral, bacterial, and parasitic gastroentritis.
8Small bowel diarrhea: watery, voluminous with less than 5 WBC/high power field
Large bowel diarrhea: Mucousy and/or bloody with less volume and more than 10 WBC/high power field
 It could be as high as 1000 based on patient's immunity system.
The table below summarizes the findings that differentiate inflammatory causes of chronic diarrhea