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Management of Cystoisospora (Isospora) infections

Karin Leder, MBBS, FRACP, PhD, MPH, DTMH
Section Editor
Peter F Weller, MD, MACP
Deputy Editor
Jennifer Mitty, MD, MPH


Cystoisospora belli (formerly known as Isospora belli) is an opportunistic protozoan that in immunocompetent patients can cause self-limited watery diarrhea. However, in immunocompromised patients, such as those with the acquired immune deficiency syndrome (AIDS), it can result in severe debilitating chronic diarrhea with wasting.

The clinical management of patients with Cystoisospora infection will be discussed here. The epidemiology, clinical manifestations, and diagnosis of Cystoisospora infection are discussed elsewhere. (See "Epidemiology, clinical manifestations, and diagnosis of Cystoisospora (Isospora) infections".)


The management of patients with Cystoisospora involves supportive treatment for the dehydration and malnutrition associated with a severe diarrheal illness. For certain patients, especially immunocompromised hosts, antibiotic therapy against the pathogen is also administered. There are special treatment considerations for HIV-infected individuals, such as early initiation of potent antiretroviral therapy and secondary prophylaxis. (See 'Secondary prophylaxis' below and 'Antiretroviral therapy' below.)


Fluid and electrolyte support — Patients with Cystoisospora infection may have evidence of severe volume depletion and electrolyte abnormalities, such as hypokalemia, hypomagnesemia, and bicarbonate wasting. Aggressive fluid resuscitation is critical with intravenous crystalloid, as well as supplementation of potassium chloride and magnesium sulfate. Cardiac monitoring may be necessary for patients with severe electrolyte imbalances. (See "Maintenance and replacement fluid therapy in adults".)

Nutritional support — It is important to address nutritional needs with parenteral nutritional support (where feasible) followed by enteral or oral feeding as soon as the patient’s clinical symptoms improve. Immunocompromised patients (eg, patients with acquired immune deficiency syndrome [AIDS]) who have chronic diarrhea from enteric pathogens often have malabsorption of fats and vitamins, which can lead to elevated prothrombin and low serum albumin levels. Malnutrition can also lead to significant thymic gland atrophy that can affect T cell mediated immune responses [1].

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Literature review current through: Sep 2017. | This topic last updated: Jul 25, 2017.
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