View source for Cystoisospora belli

== Background ==

=== Epidemiology ===
* Worldwide, but more in tropical and subtropical areas
* Can have outbreaks with daycare, animal exposures
* Mostly associated with HIV infection, but can also cause a traveller's diarrhea

=== Life Cycle ===
* '''Oocysts''' are shed into the environment
** Each contains one '''sporoblast'''
** Remain viable for months
* Oocysts sporulate in the environment before becoming infectious
** Sporoblasts dividing and maturing into two '''sporocysts''', which in turn divide and mature into two '''sporozoites''' each
* The sporulated oocyst (containing four sporozoites) is ingested
* In the proximal small bowel, the sporozoites are released and develop into '''merozoites'''
* The merozoites go through asexual reproduction, eventually followed by sexual reproduction that results in development of an immature oocyst, which is shed

== Clinical Presentation ==
* Incubation period of 1 week
* Watery diarrhea with abdominal cramping, malaise, anorexia, and weight loss
* Fever, if it occurs, is low-grade
* One of the only intestinal protozoa that can cause a peripheral '''eosinophilia'''
* Lasts 2 to 3 weeks, but can continue to shed oocysts for weeks after

=== Immunocompromised patients ===

* Includes HIV (CD4 <200) and chemotherapy
* Disease course may be more severe and may be chronic
* Can include '''hemorrhagic colitis'''

== Management ==
* In HIV patients:
** [[Is treated by::Trimethoprim-sulfamethoxazole]] DS po qid for 10 days
** Alternative: [[Is treated by::ciprofloxacin]] 500 mg po bid for 7 days then three time weekly, [[Is treated by::pyrimethamine]] 75 mg po daily with folinic acid, or [[Is treated by::nitazoxanide]]

{{DISPLAYTITLE:''Cystisospora belli''}}
[[Category:Protozoa]]
[[Category:Gastrointestinal infections]]