Cyclosporiasis describes the condition of being infected with the coccidian protozoan parasite Cyclospora cayetanensis. The main symptom of infection in an immunocompetent host is a self-limiting diarrhea. An infected immunocompromised patient will have chronic diarrhea and rarely acalculous cholecystitis. Children in underdeveloped countries and travelers are especially susceptible to recurrent diarrhea illness. It is an emerging infectious disease with increased incidence rates over the last 20 years. Diagnosis is made by analyzing stool samples for oocysts. Trimethoprim/sulfamethoxazole is an effective treatment. Ciprofloxacin or nitazoxanide are alternative treatments.
Incubation lasts between 7 and 14 days after consuming sporulated oocysts. The primary symptom is profuse, malodorous, watery, and non-bloody diarrhea. This type of diarrhea is seen in many other types of GI infection and is indistinguishable from Cryptosporidium or Isospora infections. Additionally, the patient may suffer from the associated symptoms of abdominal cramps, nausea, loss of appetite, malaise, fatigue, dehydration, and weight loss . Malabsorption and low grade fever are also possible. These symptoms are self-limiting in a patient with a healthy immune system, but remission is common. The condition may last several weeks. These symptoms are more aggressive in children. The symptoms of cyclosporiasis in patients with a depressed immune system are more aggressive and should be treated with antibiotics. Additionally, these patients may develop acalculous cholecystitis with right upper quadrant pain and tenderness   .
The mortality rate from cyclosporiasis is very low. Infection in an immunocompetent patient is usually self-limiting. The severe, though short lived, diarrhea associated with this infection can lead to severe dehydration and malnutrition, especially in children. Full recovery in this population is expected but reinfection is possible. Treatment with antibiotics can speed recovery and reduce oocyte shedding, but is usually not necessary. In an immunosuppressed patient, infection is chronic. Dehydration and malnutrition can lead to weight loss. Additionally, this population can develop acalculous cholecystitis. Antibiotics are usually required to treat the infection and prophylactic antibiotics may be necessary to prevent reinfection.
Cyclosporiasis is caused by ingestion of sporulated Cyclospora cayetanensis oocysts. They are often found in fecal contaminated water or sewage, especially in the underdeveloped world. Travelers to these areas are very susceptible . However, cyclosporiasis is becoming more common in the developed world as well. The immunocompromised population is at risk of developing chronic cyclosporiasis.
C. cayetanesis oocysts are frequently isolated in individuals from developing countries or travelers returning from these countries  . Infection prevalence in endemic areas is between 2-18%. Endemic areas include Guatemala, Haiti, Nepal, and Peru. In developed countries the prevalence is between 0.1% - 0.5% . The incidence rate in the developed world is increasing. Cases of infection are often associated with contaminated food or water and travelers returning from endemic areas.
Cyclospora measure 8-10 micrometers in diameter, are round to ovoid in shape, and variably acid-fast. As part of their life cycle, they require about 7 days outside the human GI tract to sporulate. Two infectious sporocysts are produced for every one immature, noninfectious oocyst. Transmission occurs after the sporocysts are ingested, usually in feces infected water or contaminated food. Incubation takes 7-14 days after consumption. Two sporozoites emerge from each sporocytsts and invade the enterocyte lining of the GI tract in the small intestine. The sporozoites have an anterior polar complex that is required to enter the host’s enterocytes. The precise mechanism is not known.
In the enterocytes of the jejunum and ileum of the small intestine the parasite replicates asexually to form type I and type II meronts. Type II meronts mature into male mircogametocytes and female macrogametocytes. The microgametocyte fertilizes the microgametocyte, still while inside the intestinal epithelial cell. Unsporulated oocysts are formed and escape the intracellular space into the lumen of the GI tract, where they are excreted with the stool to continue the cycle. Cyclospora unsporulated oocysts may be confused with cryptosporidium oocysts because they are both acid fast, but cryptosporidium (4-5 um) are about half the size of Cyclospora oocysts (8-10 um) . Cryptosporidium oocysts are also instantly infectious where Cyclospora oocysts are not  . Experiments to infect various animals species with Cyclospora cayetanensis were unsuccessful, suggesting the need for a specific, unknown trigger to initiate infection .
While traveling abroad in underdeveloped countries do not consume untreated water or ice and do not eat unpeeled fruits and vegetables which can be contaminated. Thoroughly heating foods and boiling water effectively neutralizes the parasite and will prevent infection. Hand hygiene is also essential.
Cyclospora are single celled coccidian protozoa. They are found throughout the world and infect many different types of animals including mammals and reptiles. Humans are the only recognized hosts for C. cayetanesis. Cyclosporiasis is classified as an emerging infectious disease. The parasite is infectious to both immunocompetent and immunocompromised hosts. In the immunocompromised, it produces a chronic disease. Infection is limited to the gastrointestinal (GI) tract and is characterized by a profuse, malodorous, and watery diarrhea with nausea, abdominal cramping, bloating, and fatigue. Symptoms can last up to 2 months. Explosive diarrhea is also possible. Similar GI symptoms are found in other parasite infections from Cryptosporidium or Isospora. The route of transmission is person to person as oocysts are released in the stool. A fresh stool sample is not communicable, they require about 1 week outside the GI tract to sporulate before they are infectious . A person with an active C. cayetanesis infection may be asymptomatic but still excrete oocysts.
Cyclosporiasis describes an intestinal infection caused by Cyclospora cayetanensis. It is more commonly found in the developing world, especially in children, and in travelers to these parts of the world; however, it is an emerging infectious disease in the developed world.
Transmission is caused by ingestion of water or food contaminated with fecal material that contains Cyclospora oocysts. Incubation is 1-2 weeks after ingestion of infectious oocytes.
Signs and symptoms
Cyclosporiasis is diagnosed by stool examination. Multiple stool samples may need to be analyzed to find an oocyte.
Most patients with a healthy immune systems (immunocompetent) will recover without treatment, though antibiotics will ameliorate symptoms (especially the diarrhea). Patients with a compromised immune system (HIV/AIDS, chemotherapy for cancer, anti-rejection medication after an organ transplant) may develop a chronic disease and will require antibiotic treatment and prophylaxis to prevent future disease. Treatment consists of the combination of trimethoprim and sulfamethoxazole. Ciprofloxacin and nitazoxanide are equivalent alternative treatments.