The dissemination of infective Cyclospora oocysts via water, soil, and unprocessed foods (e.g., fruits and vegetables, including ready-to-eat salads) is enabled by their small size (8–10 cm), low specific gravity, and high infectivity. Such oocysts can survive for weeks to months in water and food, depending on the environmental temperature, and are resistant to the routine sanitization or chemical disinfection procedures used in irrigation systems, recreational waters, or drinking water treatment plants.
Cyclospora infects the small intestine (bowel) and usually causes watery diarrhea, bloating, increased gas, stomach cramps, flatulence, loss of appetite, nausea, low-grade fever, and profound fatigue. In some cases, vomiting, explosive diarrhea, muscle aches, and substantial weight loss can occur. The incubation period between acquisition of infection and onset of symptoms averages ~1 week (ranges from~2–14 or more days); however, some people who are infected with Cyclospora do not have any symptoms.
Cyclosporiasis is usually diagnosed symptomatically in clinical settings, including the presence of watery diarrhea, abdominal cramping, and bloating. In untreated, immunocompetent people, the diarrhea can last from days to weeks to a month or more and can wax and wane, with variable oocyst shedding. Oocysts can continue to be shed (intermittently or continuously) by non-symptomatic people, and symptoms can also persist in the absence of oocysts in feces. In a clinical context, conventional diagnosis usually involves microscopic examination of intestinal tissue biopsy sections, stool samples for the presence of developmental stages of Cyclospora, or advanced molecular testing for DNA. Improved specificity and sensitivity have been possible largely using PCR (polymerase chain reaction), which enables the specific amplification of genetic loci from tiny amounts of genomic DNA of Cyclospora. Because of the intermittent nature of oocyst shedding and the low numbers of this stage in feces, it is recommended that multiple stool samples be collected at 2–3-day intervals over a period of more than a week, to increase the likelihood of identifying the disease microscopically.
Cyclospora infection is typically self-limited but may be prolonged and accompanied by progressive fatigue and weight loss. According to the CDC, the recommended treatment is a combination of two antibiotics: trimethoprim-sulfamethoxazole, also known as Bactrim, Septra, or Cotrim. It is advisable for people who have diarrhea to also rest and drink plenty of fluids. No equally effective treatments have been identified yet for people with Cyclospora infection who are unable to take sulfa drugs, such as those with allergies, pregnant or breastfeeding women, or pediatric patients. Some experimental studies, however, have suggested that ciprofloxacin or nitazoxanide may be effective, although to a lesser degree than trimethoprim-sulfamethoxazole.