Cyclospora: clinical and travel guidance
Source: gov.uk (2025-07-15)

Travel and clinical advice on Cyclospora including characteristics, symptoms, diagnosis and epidemiology.

This content was originally produced by Public Health England (PHE). This content is now owned and managed by the UK Health Security Agency (UKHSA)

There are several species of Cyclospora but only Cyclospora cayetanensis is known to cause diarrhoeal illness in humans. It is an intestinal coccidian protozoal parasite that occurs predominantly in tropical and subtropical regions of the world, and is also an emerging cause of travellers’ diarrhoea.

Epidemiology

Cyclospora was first identified in 3 patients with a diarrhoeal illness in Papua New Guinea in 1979. In the 1980s and early 1990s, the parasite was found in samples from several patients with diarrhoea, mostly in travellers to endemic areas and AIDS patients. The organism was later named Cyclospora cayetanensis in 1993.

The epidemiology of C. cayetanensis is not fully understood, but it is thought to occur predominantly in tropical and subtropical regions of the world. Infection rates of between 0 and 13% (http://www.ncbi.nlm.nih.gov/pubmed/20382099) have been documented in countries in South and Central America, South and South East Asia, the Middle East and Africa. It can affect both children and adults.

Outbreaks of C. cayetanensis are most commonly reported in non-endemic countries and have been associated with travel to an endemic area or with an imported fresh food. Raspberries, snow peas, lettuce, basil, cilantro (leaf coriander) and field greens have been implicated as the vehicles of infection for several reported outbreaks (http://www.ncbi.nlm.nih.gov/pubmed/11049789) in Europe, the United States and Canada. Drinking untreated water has also been associated with outbreaks reported in endemic areas.

Symptoms

Symptoms of Cyclospora infection typically begin 7 days after ingestion of sporulated oocysts (the infective form of the parasite). Infection with Cyclospora may be asymptomatic or mild in some people particularly in endemic areas. Some people have a flu-like illness for a few days initially, followed by rapid onset of gastrointestinal symptoms. Typical symptoms include:
- watery diarrhoea
- fatigue and muscle pain
- loss of appetite
- weight loss
- cramping
- abdominal wind or bloating
- nausea
Illness caused by Cyclospora is self-limiting in most people, but can be prolonged for 6 weeks or so and particularly severe in those who are immunocompromised, such as those with HIV infection.

Transmission

Cyclospora is acquired by ingesting food or water that is contaminated with sporulated oocysts. Once the oocysts are ingested they travel to the gut where sporozoites (mobile form of the parasite) are released, invade cells in the gut and multiply inside them causing symptoms. The parasites then undergo sexual development in the gut forming unsporulated oocysts, which are then excreted in faeces. These unsporulated oocysts must undergo sporulation (mature into an infective form) in the environment before they can cause illness in humans. The exact mechanism of this is not fully understood, but it is likely to be temperature dependent, and it can take at least 10 days.

Direct human to human transmission or transmission by ingesting food or water contaminated with fresh human faeces does not occur.

Diagnosis and treatment

Returning travellers with symptoms should contact their GP for further assessment and management. Diagnosis is made by detection of Cyclospora oocysts by undertaking stool microscopy. However, if appropriate screening algorithms are not followed, cases can go undetected. Faecal samples can be examined at the local laboratory using a wet preparation and a concentration technique. Any structures resembling Cyclospora are further examined under UV light for parasite autofluorescence or confirmed using modified Ziehl-Neelson and accurate measurement. Specimens should be referred to the PHE National Parasitology Reference Laboratory, Hospital for Tropical Diseases, for confirmation and typing.

While most cases have self-limiting symptoms, severe or prolonged infection can be treated with the antibiotic co-trimoxazole.

Prevention and advice for travellers

Infection with Cyclospora occurs after ingesting fresh food or water contaminated with Cyclospora oocysts. Travellers should follow good food and water hygiene advice (https://travelhealthpro.org.uk/factsheet/44/food-and-water-hygiene) at all times on holiday, particularly in tropical and subtropical areas, even if staying in high-end, all-inclusive resorts. Travellers should avoid food that cannot be washed in treated water or cooked. Foods often involved in Cyclospora outbreaks include soft fruits like raspberries and salad or herb products such as coriander, basil and lettuce.

Travellers should only use bottled or treated water for drinking and cleaning teeth. Ice in drinks should be avoided unless from a treated water source. Remember that drinks may also contain uncooked herbs, vegetables or fruit.

See Cyclospora advice for travellers (https://www.gov.uk/government/publications/cyclospora-advice-for-travellers)

Further information for the public on Cyclospora is available on NHS Choices (https://www.nhs.uk/conditions/cyclospora/).

Cyclospora in the UK

Between 2005 and 2014, on average, 32 cases of Cyclospora were reported in England and Wales each year. Of these, country or region of travel was known for around a quarter of all cases. Cases most commonly had reported travel to South and South East Asia and South and Central America.

In 2015, an increase in cases returning from Mexico was reported in the UK and Canada. Between 1 June and 22 September 2015, a total of 79 cases were reported in the UK (England, Scotland and Wales) that were associated with travel to Mexico (mainly to the Riviera Maya); a similar outbreak occurred in 2016 involving 443 UK cases.