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Cyclosporiasis refers to infection by the sporeforming protozoan known as Cyclospora. Protozoa are a group of parasites that infect the human intestine. Parasites are organisms that live in another body, called the host, and get food and liquids from that host. This parasite is a member of the group of protozoa known as coccidia, to which Cryptosporidia also belongs. This group of parasites infects the human intestine, and causes chronic recurrent infections in those with altered immunity or AIDS. Even in people with normal immune function, Cyclopsora can cause prolonged bouts of diarrhea and other gastrointestinal symptoms.


Until recently, Cyclospora was considered to be a form of algae. The parasite causes a common form of waterborne infectious diarrhea throughout the world. Just how the parasite gets into water sources is not yet clear. It is known that ingestion of small cysts in contaminated water leads to disease.

Causes and symptoms

Symptoms begin after an incubation period of about a day or so following ingestion of cysts. A brief period of flu-like illness characterized by weakness and low-grade fever is followed by watery diarrhea, nausea, loss of appetite, and muscle aches. In some patients, symptoms may wax and wane for weeks, and there are those in whom nausea and burping may predominate. It is also believed that infection can occur without any symptoms at all.
In patients with abnormal immunity (immunocompromised patients), such as those with AIDS and cancer, prolonged diarrhea and severe weight loss often become a major problem. The bile ducts are also susceptible to infection in AIDS patients.


The disease should be suspected in anyone with a history of prolonged or recurrent diarrhea. The parasite is identified either by staining stool specimens or by applying certain fluorescent ultraviolet techniques to find the characteristic cysts. Biopsy of an infected organ such as the intestine through an endoscope is another way to make the diagnosis.


The first aim of treatment as with any severe diarrheal illness is to avoid dehydration and malnutrition. Oral Rehydration Solution (ORS) or intravenous fluids are sometimes needed. Medications used to treat diarrhea by decreasing intestinal motility, such as loperamide or diphenoxylate are also useful, but should only be used with the advice of a physician.
The use of the medication, trimethoprim-sulfamethoxazole (Bactrim) for one week can be successful in treating intestinal infections and prevents relapse in those with a normal immune system. The same medicine can be prescribed to treat infections of both the intestine or bile ducts in immunocompromised individuals, but maintenance or continuous treatment is often needed.


The outlook is quite good for individuals in whom a diagnosis is made. Even without treatment, symptoms usually do not last much more than a month except in cases with altered immunity. Fortunately, treatment is usually successful even in those patients.


Aside from a waterborne source as the origin of infection, little else is known about how the parasite is transmitted. Therefore, little can be done regarding prevention, except to maintain proper hand washing techniques and hygiene.

Key terms

Anti-motility medications — Medications such as loperamide (sold as Imodium), dephenoxylate (sold as Lomotil), or medications containing codeine or narcotics that decrease the ability of the intestine to contract. This can worsen the condition of a patient with dysentery or colitis.
Cyst — A protective sac that includes either fluid or the cell of an organism. The cyst enables many organisms to survive in the environment for long periods of time without need for food or water.
Immunocompromised — A change or alteration of the immune system that normally serves to fight off infections other illnesses. This can involve changes in antibodies that the body produces (hygogammaglo-bulinemia), or a defect in the cells that partake in the immune response. Diseases such as AIDS and cancer exhibit changes in the body's natural immunity.
Oral Rehydration Solution (ORS) — A liquid preparation developed by the World Health Organization that can decrease fluid loss in persons with diarrhea. Originally developed to be prepared with materials available in the home, commercial preparations have recently come into use.
Parasite — An organism that lives on or in another and takes nourishment (food and fluids) from that organism.
Protozoa — Group of extremely small single cell (unicellular) or acellular organisms that are found in moist soil or water. They tend to exist as parasites, living off other life forms.
Spore — A resistant form of certain species of bacteria, protozoa, and other organisms.



Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311.


"Cyclospora." Centers for Disease Control.


Infection with Cyclospora.


/cy·clo·spo·ri·a·sis/ (-spah-ri´ah-sis) infection by protozoa of the genus Cyclospora, especially C. cayetanen´sis, seen especially in immunocompromised patients and occurring as recurrent gastrointestinal disease and watery diarrhea.


n. pl. cyclospori·ases (ə-sēz′)
Intestinal infection with a protozoan parasite, Cyclospora cayetanensis, that is transmitted by contaminated food or water, characterized by diarrhea, nausea, fatigue, and abdominal cramps.


Infectious disease Infection with Cyclospora spp, in particular C cayetanensis Vector Poorly cleaned imported fruits & vegetables Clinical Protracted diarrhea described as profuse, malodorous, watery, and can cause dehydration and weight loss; the diarrhea may be associated with nonspecific complaints–eg, intermittent abdominal colic, N&V, low-grade fever, malaise, myalgias, anorexia, bloating, flatulence, and/or profound fatigue, clinically identical to Cryptosporidium and Isospora infections Management TS for 1 wk; AIDS Pts require longer therapy. See Traveler's diarrhea. Cf Cryptosporiasis.
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Observations in the present study extend our knowledge of the geographic and host range for cyclosporiasis.
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