Cyclospora cayetanensis morphology, life cycle and treatment

Simon Doyle

The cyclospora cayetanensis it is a microscopic parasite that belongs to the group of protozoa. It is responsible for thousands of cases of persistent and chronic diarrhea annually in endemic countries. It is transmitted through contaminated water or food, which contains a mature evolutionary form capable of transmitting the infection called a sporulated oocyst.

Humans are the only living being that can become infected, by ingesting contaminated food or water, releasing in their intestines the evolutionary form of the parasite that is responsible for its reproduction: the sporozoite..

Photomicrograph showing the presence of four Cyclospora cayetanensis oocysts

Through reproduction, non-sporulated oocysts are released, which will be excreted through the feces, and contaminate the environment, where they later mature, towards their infectious evolutionary form..

Cyclosporiasis is the disease produced by Cyclospora cayetanensis, this consists of a clinical picture characterized by diarrhea, nausea, vomiting, abdominal distention, flatulence, and fever.

Treatment consists of administering Trimeroprim Sulfamethoxazole for 7 days, although there are other therapeutic options in case of allergies..

Article index

  • 1 Morphology and discovery
    • 1.1 Morphology
    • 1.2 Discovery
  • 2 Life cycle and transmission
  • 3 Symptoms of cyclosporiasis
  • 4 Risk factors for Cyclospora cayetanensis infection
  • 5 Treatment
  • 6 References

Morphology and discovery


Cyclospora cayetanensis is a parasite that belongs to the group of protozoa. They are very small parasites, which can only be seen with a microscope..

Its morphology is characterized by presenting as spherical oocysts of 8-10 nanometers in diameter, covered by a thick wall. They contain 2 sporocysts inside, of which each contains 2 sporozoites, which are responsible for causing the infection.

It belongs to the phylum Apicomplexa, subclass Coccidiaina and family Eimeriidae. Although approximately 13 types of Cyclospora have been described, Cyclospora cayetanensis is the only one that has been known to infect humans..


The parasite was described in the year 1979 in humans, when a scientist named Ashford found a germ similar to coccidia in the feces of some people in New Guinea..

It was not until 15 years later, when Ortega et al. (1994) published an article in which they had been able to emulate the reproductive cycle of the parasite, calling it Cyclospora cayetanensis and describing its morphological characteristics..

From then on, it would be the subject of multiple studies due to its similarity with other parasites, and the disease it produces..

Life cycle and transmission

By Franciscosp2 (self-made (using xfig and Linux).) [GFDL ( or CC BY-SA 4.0 ( by-sa / 4.0)], via Wikimedia Commons

The life cycle of Cyclospora cayetanensis begins when a human ingests sporulated oocysts through contaminated food or water, which upon reaching the digestive tract release sporozoites.

In its intestinal cycle, the sporozoite invades the epithelial cells of the human digestive tract, remaining within them to reproduce asexually, forming merozoites that later go on to reproduce sexually through female and male gametes, producing a zygote that matures. in an oocyst.

The oocyst (not sporulated) breaks the cell, is released into the intestinal lumen and remains in the fecal matter until it is expelled, where it comes into contact with the environment..

The non-sporulated oocyst remains in the environment for a period of 2 weeks. A temperature of 22 to 32 ° C is necessary for optimal sporulation of the oocyst to occur.

For this reason, the infection does not occur in direct person-person contact through fecal-oral transmission, but rather through the ingestion of food or water that contains sporulated oocysts in the environment..

Symptoms of cyclosporiasis

Cyclosporiasis is the disease caused by Cyclospora cayetanensis. It is a clinical picture characterized by presenting gastrointestinal symptoms such as:

  • Watery diarrhea: They are liquid stools with great loss of water and electrolytes. They occur in number from 5 to 15 per day, and are the cause of persistent and chronic diarrhea, diarrhea lasting on average 30 to 50 days in previously healthy people.
  • Anorexy: in most cases loss of appetite is described secondary to the other symptoms that occur.
  • Nausea and vomiting.
  • Weightloss: weight loss is associated with the immune status, since in patients with HIV / AIDS it is accentuated more than in previously healthy ones.
  • Bloating and abdominal pain: abdominal pain is crampy, post-feeding and mild to moderate in intensity.
  • Flatulence.
  • Fever: they are low-temperature fevers with no hourly predominance.

In some cases the infection by the parasite may occur and not present symptoms, this situation is known as the case of "asymptomatic carrier".

Once the sporulated oocysts are ingested, the infectious process has an incubation period that lasts from 7 to 15 days. In this period there are no symptoms of cyclosporiasis.

The severity of the symptoms will depend on several factors: the patient's immune status, age, and other associated diseases..

Symptoms can vary from very mild, in individuals from endemic areas for the parasite, to severe, in immunocompromised patients and travelers..

Risk factors for Cyclospora cayetanensis infection

Cyclospora cayetanensis is more frequent in tropical and subtropical areas, in less developed countries, where hygienic conditions and sanitation of public waters do not comply with strict regulations. Similarly, people who travel to these endemic areas are at risk..

Countries with frequent cyclosporiasis outbreaks are Haiti, Guatemala, Peru, Nepal, Indonesia, China, Mexico, Honduras, the United States, and Canada..

The time of year is associated with cyclosporiasis outbreaks. Spring and summer are the times when more cases of cyclosporiasis are reported, also associated with the importation of contaminated fruits and vegetables from endemic countries..

Some animals, such as pigeons, can transmit it, through contact with contaminated feces or water, so the presence of these animals near water sources represents a risk factor for the disease..

Young children who play in sandboxes, or open areas, especially in endemic areas, are at risk of being infected by polluted waters.


The treatment of choice for cyclosporiasis is an antimicrobial called Trimethoprim Sulfamethoxazole. It must be kept at least 7 days to guarantee the elimination of oocysts in the stool.

In people allergic to trimethoprim silfamethoxazole, the therapeutic options of Ciprofloxacin and Nitasuxonide are available, although they are not as effective as the first..


  1. Barbara L. Herwaldt (2000) Cyclospora cayetanensis: A Review, Focusing on the Outbreaks of Cyclosporiasis in the 1990s. Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia. Recovered from:
  2. Yne's R. Ortega, Roxana Sanchez (2010) Update on Cyclospora cayetanensis, a Food-Borne and Waterborne Parasite. Clinical microbiology reviews, Jan. 2010, p. 218-234 Recovered from:
  3. (2013) Cyclospora cayetanensis. Publication available at:
  4. Chacin-Bonilla, L. 2017. Cyclospora Cayetanensis. Michigan, USA. Recovered from:
  5. Wikipedia. Cyclospora cayetanensis. Updated August 4, 2018.Available at:
  6. Centers for disease, control and prevention. Parasites - Cyclosporiasis (Cyclospora Infection). Updated June 7, 2018.Available at:

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