Cyclosporiasis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Kalsang Dolma, M.B.B.S.[2]
Overview
Cyclosporiasis is an intestinal illness caused by the protozoan Cyclospora cayetanensis, which is transmitted by feces or feces-contaminated fresh produce and water. Outbreaks have been reported in imported raspberries. Fortunately it is not spread from person to person. It is commonly the cause of diarrhea for many travelers.
Pathophysiology
When freshly passed in stools, the oocyst is not infective (thus, direct fecal-oral transmission cannot occur; this differentiates Cyclospora from another important coccidian parasite, Cryptosporidium). In the environment, sporulation occurs after days or weeks at temperatures between 22°C to 32°C, resulting in division of the sporont into two sporocysts, each containing two elongate sporozoites. Fresh produce and water can serve as vehicles for transmission and the sporulated oocysts are ingested (in contaminated food or water). The oocysts excyst in the gastrointestinal tract, freeing the sporozoites which invade the epithelial cells of the small intestine. Inside the cells they undergo asexual multiplication and sexual development to mature into oocysts, which will be shed in stools. The potential mechanisms of contamination of food and water are still under investigation.
Causes
Cyclospora cayetanensis has been only recently identified as a single-celled coccidian parasite. The species designation was given in 1994 to Peruvian isolates of human-associated Cyclospora. It appears that all human cases are caused by this species.
Differential Diagnosis
Cyclosporiasis must be differentiated from other infectious causes of watery diarrhea.
Epidemiology and Demographics
Cyclosporiasis occurs in many countries, but the disease seems to be most common in tropical and subtropical regions. In areas where cyclosporiasis has been studied, the risk for infection is seasonal. However, no consistent pattern with respect to environmental conditions such as temperature or rainfall has been identified.
Risk Factors
People of all ages are at risk for infection. Persons living or traveling in tropical or subtropical regions may be at increased risk because cyclosporiasis is endemic (found) in some developing countries. Foodborne outbreaks of cyclosporiasis in the United States and Canada have been linked to various types of imported fresh produce.
Natural History, Prognosis and Complications
The symptoms usually start within one week of ingestion of contaminated food and water. If left untreated, symptoms may persist for weeks and months. This infection is not life threatening and is rarely associated with complications. People living in endemic area might have asymptomatic infections.
Diagnosis
History and Symptoms
Symptoms of cyclosporiasis start approximately 7 days following ingestion of water and food contaminated with sporulated oocysts. The most common symptom is watery diarrhea. Other symptoms include loss of appetite, cramping, flatulence, fatigue, low-grade fever, nausea and vomiting.
Physical Examination
The diagnosis of cyclosporiasis is mainly clinical relying on the history of symptoms. There are no specific physical findings. A patient might have non specific signs of dehydration, fatigue and fever.
Laboratory Findings
Health care providers should consider Cyclospora as a potential cause of prolonged diarrhea, particularly in patients with a history of recent travel to Cyclospora endemic areas. Testing for Cyclospora is not routinely done in most U.S. laboratories, even when stool is tested for parasites. Therefore, if indicated, health care providers should specifically request testing for Cyclospora. Cyclospora infection is diagnosed by examining stool specimens. Diagnosis can be difficult in part because even persons who are symptomatic might not shed enough oocysts in their stool to be readily detectable by laboratory examinations. Therefore, patients might need to submit several specimens collected on different days. Special techniques, such as acid-fast staining, are often used to make Cyclospora oocysts more visible under the microscope. In addition, Cyclospora oocysts are autofluorescent, meaning that when stool containing the parasite is viewed under an ultraviolet (UV) fluorescence microscope the parasite appears blue or green against a black background. Molecular diagnostic methods, such as polymerase chain reaction (PCR) analysis, are used to look for the parasite's DNA in the stool.[1]
Treatment
Medical Therapy
Trimethoprim-sulfamethoxazole (TMP-SMX), or Bactrim, Septra, or Cotrim, is the treatment of choice.Most people who have healthy immune systems will recover without treatment. If not treated, the illness may last for a few days to a month or longer. Symptoms may seem to go away and then return one or more times (relapse). Anti-diarrheal medicine may help reduce diarrhea, but a health care provider should be consulted before such medicine is taken. People who are in poor health or who have weakened immune systems may be at higher risk for severe or prolonged illness.[2]
Primary Prevention
The main preventive measure against cyclosporiasis is to avoid unclean water and food that are contaminated with feces.