Cyclosporiasis

Cyclosporiasis is an infectious disease caused by Cyclospora cayetanensis, a pathogenic apicomplexan protozoan parasite that primarily infects the small intestine of humans and other primates. The organism is an obligate intracellular parasite whose life cycle requires an environmental sporulation period before becoming infectious to new hosts. First identified in human clinical cases in the late 1970s, the parasite has since been recognized as an emerging cause of foodborne illness worldwide.

Following an incubation period of approximately one week after ingestion, infected individuals develop a characteristic syndrome of severe watery diarrhea accompanied by bloating, fever, stomach cramps, and muscle aches. The parasite preferentially invades the mucosa of the jejunum, causing inflammation of the lamina propria and increased plasma cell infiltration in the intestinal wall. Oocysts may be recovered from duodenal aspirates during acute infection. While most cases resolve with appropriate treatment, chronic infection has been associated with rare neurological complications including Bell's palsy, though this represents an uncommon sequela.

Human cyclosporiasis was first documented in 1977-1979 when three cases were identified in Papua New Guinea by British parasitologist Ashford, who noted the parasite's unusually long sporulation period of 8-11 days. The disease has since been recognized globally, with numerous outbreaks traced to contaminated fruits and vegetables. The requirement for environmental sporulation means that direct person-to-person transmission is highly unlikely, though travelers to endemic areas face elevated risk. The parasite enters the environment primarily through contamination of water sources or soil fertilized with human feces.

Cyclosporiasis is transmitted via the fecal-oral route through ingestion of food or water contaminated with sporulated oocysts. Outbreaks have been repeatedly associated with consumption of contaminated fresh produce, including various fruits and vegetables. A critical feature of transmission biology is that freshly shed oocysts are not immediately infectious; they require 1-2 weeks in the environment to sporulate and become capable of establishing infection. This requirement substantially limits direct person-to-person spread and distinguishes cyclosporiasis from some other intestinal protozoan infections.

Travelers to regions with inadequate water treatment and sanitation infrastructure face elevated risk of infection through consumption of contaminated food or water. Individuals consuming raw or minimally processed fresh produce, particularly in outbreak settings, represent a significant exposure group. Immunocompetent hosts typically experience self-limited illness, though the disease can cause prolonged symptoms lasting weeks without treatment. The parasite's host range is limited primarily to humans and other primates, distinguishing it from some zoonotic intestinal parasites.

Prevention centers on avoiding exposure to potentially contaminated food and water sources. Travelers to endemic regions should consume only thoroughly cooked foods and avoid drinking untreated surface water. Proper washing and cooking of fresh produce can reduce transmission risk, though the oocyst's environmental hardiness complicates control efforts. No vaccine is currently available for prevention of human cyclosporiasis, though vaccines exist for veterinary use in reducing fetal losses in sheep.

Surveillance for cyclosporiasis requires awareness of the disease's distinctive epidemiology, as cases often present in travelers or as outbreak clusters linked to common food sources. Laboratory diagnosis is challenging because unsporulated oocysts in stool specimens may be mistaken for fungal spores and are otherwise difficult to recognize. Confirmation typically requires specialized techniques including acid-fast staining or PCR-based DNA testing. The relatively recent recognition of this pathogen in humans means that historical surveillance data may underestimate true disease burden.

1. 1 Wikidata. cyclosporiasis.
2. 2 Wikipedia. Cyclosporiasis - Wikipedia.

ICD-10

ICD-11

Total cases

7K

Peak month

2019-07

Coverage

1 reporting countries · 2019-01-12 → 2026-05-09