Cyclospora Infection

  • Medical Author:

    Sandra Gonzalez Gompf, MD, FACP is a U.S. board-certified Infectious Disease subspecialist. Dr. Gompf received a Bachelor of Science from the University of Miami, and a Medical Degree from the University of South Florida. Dr. Gompf completed residency training in Internal Medicine at the University of South Florida followed by subspecialty fellowship training there in Infectious Diseases under the directorship of Dr. John T. Sinnott, IV.

  • Medical Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

Cyclospora infection (cyclosporiasis) facts

  • Cyclospora is a small parasitic organism. It is passed to humans when they ingest food contaminated with feces from an infected person.
  • It is most common in tropical countries, and imported foods such as lettuce have caused outbreaks in the United States. Travelers to tropical or subtropical countries are at risk, although the risk is relatively low.
  • Diarrhea is the most common symptom, often accompanied by cramping abdominal pain and fatigue. If left untreated, the diarrhea can last for several weeks.
  • The recommended treatment is a seven- to ten-day course of oral trimethoprim-sulfamethoxazole (Bactrim, Septra, Cotrim).
  • Complications are uncommon, but it is important for patients to drink lots of fluids to prevent dehydration.
  • Prevention efforts are focused on improving the safety of the food supply. Cyclospora requires a period of time outside the body to become infectious. The organism is not spread directly from person to person.

What is a Cyclospora infection?

Cyclospora infection is a diarrheal illness that occurs when humans accidentally ingest the Cyclospora parasite. This happens by eating or drinking items contaminated with soil or water.

What causes a Cyclospora infection?

Cyclospora cayetanensis is a parasite that cycles between the environment (soil) and humans during its life cycle. It survives for long periods of time in nature as an oocyst. The oocyst can resist extreme temperatures and the usual levels of chlorine in treated water. When temperatures warm, the oocyst matures and produces the infectious form, called sporozoites. When sporozoites are ingested by a human, they multiply in the gut and form new oocysts. These are excreted in feces, starting the cycle all over again.

What are the risk factors for a Cyclospora infection?

Cyclospora causes disease throughout the world, but it is commonest in tropical and subtropical climates. Outbreaks in cooler areas are often caused by food imported from warmer climates. Food is at risk if exposed to soil or water that is contaminated with human feces. Produce like lettuce, raspberries, basil, and snow peas have caused past outbreaks. In 2013, an outbreak involved many states, including Texas, Iowa, and Nebraska. It affected hundreds of people and was at least partially caused by bagged lettuce grown in Mexico. There have been small outbreaks in 31 states with a total of 546 people diagnosed with the infection in 2015.

Although travel to a tropical or subtropical country is a risk factor for Cyclospora infection, the risk is relatively low. Cyclospora is not a major cause of travelers' diarrhea.

Is Cyclospora contagious? What is the contagious period for Cyclospora?

Cyclospora is not contagious directly from person to person. Even though the oocysts are shed in stool, they take days to weeks to mature in the environment before becoming infectious. People can only be infected by eating or drinking something contaminated with mature oocysts.

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Berry, Berry, Quite Contrary...Cyclospora Outbreaks

Outbreaks of illness in the United States causing infectious watery diarrhea, nausea, and vomiting recently have been found to be caused by a parasite called Cyclospora. Food-borne outbreaks of the illness have been reported in the U.S. since the mid-1990s.

What are the symptoms of a Cyclospora infection?

Cyclospora causes watery diarrhea that lasts more than a week, up to four weeks or more. Cramping and fatigue are common. The infected person may have five to 15 bowel movements per day. Also common are fevers, belly pain, heartburn, nausea, increased gas, decreased appetite, and weight loss. Symptoms are worse in those with weak immune systems, such as people with acquired immunodeficiency syndrome (AIDS).

What is the incubation period for a Cyclospora infection?

The incubation period (the time between swallowing the oocysts and the start of symptoms) is two to 14 days, or an average of 10 days.

What types of specialists treat Cyclospora infections?

Most people with persistent diarrhea will probably be evaluated first by a primary-care provider, such as an internist, pediatrician, family medicine doctor, or nurse practitioner. As diarrhea continues beyond a couple of weeks, referrals may be made to a gastroenterologist or an infectious-disease doctor for further evaluation and treatment.

How do health-care professionals diagnose a Cyclospora infection?

Most cases of diarrhea are caused by viruses or bacteria that produce a short period of illness and resolve without specific treatment. Most people are not sick long enough to go to the doctor and have tests performed. If a person has diarrhea that is persisting beyond a week or so, there are a number of possible causes. Food, travel, and antibiotic exposures should be discussed with a doctor, who may order stool studies. Cyclospora is diagnosed by examining the stool under a microscope and finding oocysts. Even with a lot of diarrhea, oocysts may be hard to find, because oocysts are not shed continuously. At least three stool samples should be collected 24-48 hours apart. To increase the ability to diagnose Cyclospora, special staining methods, polymerase chain reaction (PCR) tests, and stool specimen concentration techniques are used. Physicians must alert the laboratory to look for Cyclospora if ordering stool studies, because these tests are not routine. There is no blood test that can detect Cyclospora.

What is the treatment for Cyclospora infections?

Cyclospora infection often goes away by itself, and mild or asymptomatic cases require no treatment. For those who require treatment, the best option is oral trimethoprim-sulfamethoxazole (TMP-SMX) (Bactrim, Septra) twice daily for seven to 10 days. For those who continue to have symptoms or have persistent oocysts on stool examination, another seven-day course is usually effective. For people with a sulfa allergy, there are few good options. There are reported cases where nitazoxanide (Alinia) twice daily was successful as an alternate therapy. One small study suggested that ciprofloxacin (Cipro, Cipro XR, ProQuin XR) twice daily for seven days is an option in adults. However, it has a higher failure rate compared to TMP-SMX. These medications are not approved for routine use in pregnancy. Pregnant women should check with their obstetrician (ob-gyn doctor) before taking any new prescription.

What are complications of a Cyclospora infection?

Profuse, watery diarrhea may cause dehydration. Thus, keeping up with fluids is important. Diarrhea also contains salts and potassium, so drinking fluids that contain electrolytes (such as sports drinks) may be beneficial. Some people feel loss of energy for some time after the diarrhea goes away.

What is the prognosis of a Cyclospora infection?

The prognosis of Cyclospora infection is excellent and complete recovery is anticipated. As discussed above, recovery can be hastened by the use of antibiotics in symptomatic people.

Patients who are infected with the human immunodeficiency virus (HIV), however, may relapse after treatment is stopped and should be referred to an infectious-disease doctor.

Is it possible to prevent Cyclospora infections?

General food-safety practices are important to prevent many infections, especially while traveling in areas where sanitation is uncertain. Wash hands in disinfected or fizzy water, or use alcohol-based hand sanitizer before eating. Cooked food that is served steaming hot is generally safe, but undercooked or raw fruits and vegetables pose a risk of Cyclospora and other infections. A good rule of thumb is to avoid raw fruits and vegetables that you have not washed and peeled with your own cleaned hands, using disinfected or factory-sealed bottled water. Bottled or canned fizzy drinks are safe to drink and wash with; bubbles mean the bottle has not been refilled with tap water and sealed with glue. If a water filter is used, it must be labeled as effective against cysts or particles up to 1 micron (a measure of length equal to one millionth of a meter). Foods that have been handled raw, such as salsas, salad greens, or cut-up fruit on a platter, are best avoided. Street vendors are iffy. Make sure you see the food taken right off the grill, and that it is not touched before giving it to you.

Since many foods are grown or prepared outside the U.S., it is important to consider food safety at home as well. Packaged raw vegetables and fruits, especially with extra handling (for example, chopped bagged salads), should be thoroughly rinsed even if labeled as triple washed.

You can be infected with Cyclospora more than once if you ingest contaminated food or water. Currently, there is no available vaccine to prevent Cyclospora infection.

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Medically Reviewed on 9/23/2016

United States. Centers for Disease Control and Prevention. "Food and Water Safety." Oct. 20, 2015. <>.

United States. Centers for Disease Control and Prevention. "Parasites -- Cyclosporiasis (Cyclospora Infection)." Jan. 10, 2013. <>.

Wright, S.G. "Protozoan Infections of the Gastrointestinal Tract." Infect Diseases of North America 26 (2012): 323-339.

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