Cyclospora Infection (Cyclosporiasis)

What Is Cyclospora Infection (Cyclosporiasis)?

  • The Cyclospora parasite causes cyclosporiasis (an intestinal illness) when humans ingest contaminated water or food containing Cyclospora sporulated oocysts.
  • Symptoms and signs of Cyclospora infections include watery diarrhea, gas, cramping, bloating, nausea, weight loss, appetite loss, and fatigue.
  • Medical care should be sought if symptoms last a week or more, if a person has traveled through an endemic area, or if they become dehydrated and weak.
  • Diagnosis of Cyclospora infections require special laboratories and lab tests to detect the parasites.
  • The only CDC-recommended treatment is the antibiotic trimethoprim-sulfamethoxazole (Bactrim DS, Septra, Sulfatrim).
  • Self-care at home consists of symptomatic treatment and completing oral antibiotic therapy.
  • Follow-up is not usually required if treatment is effective, but follow-up for certain individuals is recommended.
  • The prognoses of most treated Cyclospora infections is good to excellent; the prognoses of untreated infections range from good to a few poor outcomes.
  • Complications of Cyclospora infections may include a relapsing illness, malabsorption, cholecystitis, Reiter's syndrome (reactive arthritis), dehydration, and electrolyte problems in some patients.
  • There is no vaccine to prevent Cyclospora infections; the CDC recommends avoiding water and foods contaminated with human feces and adherence to FDA guidelines for food growers and food packagers.

What Are the Causes and Risk Factors for Cyclospora Infection?

Cyclospora infection (cyclosporiasis) is caused by a parasite that infects human small intestinal tract cells. The parasite is named Cyclospora cayetanensis; it's a single-cell parasite that can only be viewed with a microscope. Older literature termed the parasites as cyanobacterium-like. The parasite was recently discovered in 1977 and only named in 1994. The parasite has a complicated life cycle that requires development in human intestinal cells. Sporulated Cyclospora oocysts are the infective stage of the parasite. Sporozoites are intestinal parasites that infect small intestine epithelial cells after oocysts spore breaks open, a process termed excystation, which is followed by several developmental steps. After development, non-sporulated oocysts, passed out of the body of an infected person in bowel movements, must mature (sporulate) in the environment before they can infect another human. Person-to-person infection may occur indirectly by the fecal-oral route only after sporocyst maturation.

Anyone at any age is at risk of getting cyclosporiasis if they ingest water or foods contaminated with sporulated oocysts. Most individuals infected live in tropical or subtropical regions. Most of the U.S. foodborne outbreaks have been relatively small and linked to imported fresh produce (raspberries, snow peas, basil, and lettuce) but not to frozen or canned produce. A large outbreak in 2013 was linked to imported salad mix and cilantro. This large outbreak involved 25 states, primarily Iowa, Nebraska, and Texas. In 2018, two large outbreaks were reported. One was due to pre-packaged vegetables produced by Del Monte, and another caused McDonald's to stop selling salads at about 3,000 locations, mainly in the Midwest.

What Are Symptoms and Signs Cyclospora Infection?

Some people in areas where cyclosporiasis is endemic (semitropical and tropical areas) may have no symptoms or signs. Many others, especially individuals that have never been exposed to the parasites typically develop symptoms about seven days after ingestion although reports range from a few days (two days) to about two weeks. The sign most commonly reported in an infected person is watery diarrhea (sometimes characterized as explosive diarrhea). Other common symptoms and signs may include gas, bloating, cramping, abdominal discomfort or abdominal pain, nausea, loss of appetite, weight loss, fatigue, flu-like symptoms, and less commonly, low-grade fever and vomiting. Unfortunately, these are all nonspecific symptoms and can be caused by many different infections and diseases. Though many of these symptoms are short-term symptoms, cyclosporiasis symptoms of food poisoning often last for weeks to months if untreated.

When Should I Call the Doctor about Cyclospora Infection?

If a person has ingested the same food or water (liquid) that someone with a diagnosis of cyclosporiasis has ingested, or has been in an area where cyclosporiasis is endemic, and develops symptoms, they should seek medical care by a health care provider. Individuals with diarrhea lasting a week or more should seek medical care unless dehydration or weakness develops sooner.

How Do Health Care Professionals Diagnose Cyclospora Infections?

Cyclospora infections are not common in the U.S., so individuals who have been in endemic areas or who have other health concerns (for example, long-term diarrhea, eating imported foods without careful washing) should inform their medical caregivers if they suspect a Cyclospora infection. In turn, medical caregivers need to alert laboratories they suspect such infections so that the stool samples will be tested specifically for Cyclospora parasites. In addition, it is likely other tests will be done to determine if other pathogens or similar parasites like Microsporidia or coccidian Isospora parasites are causing the symptoms.

Labs may need to examine and concentrate samples of stool specimens because only a low number of oocysts are shed into the feces. In addition, special stains (note that acid-fast staining of the parasite is variable), fluorescence microscopy, or PCR tests are used to find and identify the parasites.

What Is the Treatment for Cyclospora Infection?

Diagnosis is important because only one combination drug (antibiotic) is the treatment of choice, trimethoprim-sulfamethoxazole (TMP-SMX, Cotrim, co-trimoxazole, Bactrim DS and others) 160/800 mg, oral tablet, twice a day for seven to 10 days. Some immunocompromised patients may require longer treatment. If an individual is allergic to this drug, alternative antiprotozoal agents like nitazoxanide may be successful. However, these people should be evaluated by an allergist, or an infectious disease expert. In addition, the use of anti-diarrheal medications may be considered after consultation with a health care provider.

Are There Home Remedies for Cyclospora Infection?

Other that staying well hydrated, avoiding contaminated foods or water, and taking the prescribed medication, there is no self-care role for this infection.

What Is the Follow-up for Cyclospora Infection?

For most individuals who get appropriate treatment with trimethoprim-sulfamethoxazole, follow-up is not required. However, any patient who has recurrent symptoms should follow up with their treating physician. Infection does not prevent relapses or subsequent infections, especially in untreated patients with Cyclospora infections.

What Is the Prognosis for Cyclospora Infection?

In general, the prognoses for treated Cyclospora infections range from good to excellent. Usually, the infection, even untreated, is not life-threatening, although secondary problems such as dehydration or electrolyte problems and recurring symptoms can happen.

What Are the Possible Complications of Cyclospora Infection?

Usually, there are few complications that occur from Cyclospora infections. However, such complications as relapsing illness, malabsorption, cholecystitis, and Reiter's syndrome (reactive arthritis) have been reported. In addition, severe diarrhea may lead to dehydration and electrolyte problems in patients. People with a compromised immune system are more susceptible to infection and complications.

How Can I Prevent Cyclospora Infections?

According to the CDC, the best way to avoid or prevent Cyclospora infections is by avoiding foods and liquids (water) that have been contaminated with human feces. The CDC further advises that by following the published guidelines for food growers and food packagers, the chances for Cyclospora infections are substantially reduced. Compliance with such guidelines is expected in this country, but larger outbreaks are most commonly due to imported products. Unfortunately, there is no vaccine available to prevent Cyclospora infections.

Explosive diarrhea is a sign of Cyclospora infection.

What Are the Signs and Symptoms of Cyclospora Infection?


  • Diarrhea is the frequent passage of loose, watery, soft stools with or without abdominal bloating, pressure, and cramps commonly referred to as gas or flatulence.
  • Causes of diarrhea include viral and bacterial infections, as well as parasites, intestinal disorders or diseases, reactions to medications, and food intolerance.
  • The main symptom of diarrhea is watery, liquid stools.
  • Diarrhea is usually diagnosed by the appearance of the symptoms, and no tests may need to be ordered. In some cases, a doctor may order a stool culture, blood tests, a colonoscopy, or imaging tests such as X-rays or CT scans to determine an underlying cause.
  • In most cases, diarrhea can be treated at home and it will resolve itself in a few days.
Shoff, W. "Cyclospora Infection (Cyclosporiasis) Medication." Medscape. Aug. 8, 2017. <>.

United States. Illinois Department of Public Health. "Cyclospora." July 31, 2018. <>.