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This recently described parasitic organism causes diarrhoea which is usually self-limiting, but can be prolonged and persistent in patients with impaired immunity. The organism exists in a circular form, around 10 micrometers in diameter, which can survive for several weeks in the environment. In the body the organism lives in cells lining the small intestine, causing inflammation and diarrhoea.


It is usually water-borne, either by drinking or swimming in contaminated water. Occasionally outbreaks occur due to contaminated fruit and vegetables, possibly due to spraying with contaminated water prior to harvesting. An individual with Cyclospora infection excretes the organism in the faeces, spreading infection if faecal material contaminates water sources or swimming pools. The organism is resistant to many types of water treatment, including chlorination.

Regions Affected

Cyclospora is found world-wide. It was first described in Papua New Guinea, and much of the research on this infection has been conducted in Peru and Nepal. The incidence of infection is inversely related to the level of sanitation, hygiene and treatment of water supply.


Cyclospora infections can be prevented by adequate sanitation facilities to avoid contamination of water supplies and swimming water with faeces. Boiling water for a minute will kill the organism.


None available.

Symptoms and Signs

After an incubation period of around a week, Cyclospora produces often abrupt onset watery diarrhoea, associated with nausea and abdominal cramps. The diarrhoea may last up to 2 months in previously healthy individuals, with significant weight loss and dehydration. Immunosuppressed patients may have more severe illness with persistent or relapsing diarrhoea for many months.


Cyclospora infection is diagnosed by finding the organism in stool samples by microscopic examination.


Most infections in people with normal immunity are self-limiting and do not require treatment. If the diarrhoea is prolonged, or if the patient has impaired immunity, treatment with the antibiotic Septrin may be given for one week or longer if necessary. No other antibiotics have been shown to be of any benefit.

Complications and Outcome

Patients with Cyclospora infection may have prolonged diarrhoea with significant weight loss and weakness. Other bowel complications such as bowel perforation or haemorrhage do not occur since the organism is present in the most superficial layers of the intestinal wall. In patients with impaired immunity Cyclospora infection may contribute to death, but patients would be unlikely to die of Cyclospora infection alone.

By Dr Ann Chapman