Cyclosporiasis (Cyclospora cayetanensis)

An issue on everyone's mind lately is the parasite Cyclospora. The good news is that, for the overwhelming majority of healthy people, this is more of an unpleasant gastrointestinal illness than a dangerous infection. 

Cyclosporiasis is an intestinal infection caused by the protozoan parasite Cyclospora cayetanensis, acquired almost exclusively by ingesting contaminated fresh produce or water. Humans are the only known reservoir. Unlike many enteric pathogens, the parasite's oocysts require 1–2 weeks in the environment to sporulate and become infectious, making direct person-to-person transmission highly unlikely. 

Although the current U.S. outbreak has been larger than usual, serious complications remain uncommon. During the 2025 U.S. season, the CDC recorded 1,180 domestically acquired cases, 105 hospitalizations (about 9%), and no deaths. Most hospitalizations were for dehydration or inability to maintain hydration rather than invasive disease. 

Children

·     Incubation: ~1 week (range 2 days–2 weeks).

·     Prolonged watery diarrhea is the hallmark, often intermittent or relapsing.

·     Associated symptoms: (looks like every GI bug)

·     Abdominal cramping and bloating

·     Anorexia

·     Nausea/vomiting

·     Fatigue

·     Weight loss

·     Low-grade fever (about half of patients)

·     Young children may present primarily with dehydration and poor weight gain if illness is prolonged. Untreated disease may last weeks to over a month. 

Diagnosis

·     Routine stool ova-and-parasite examinations may miss Cyclospora.

·     The clinician should specifically request Cyclospora testing, preferably by multiplex PCR or modified acid-fast staining.

·     Multiple stool specimens may be necessary because oocyst shedding is intermittent. 

Treatment

·     Antibiotics: Trimethoprim-sulfamethoxazole (TMP-SMX) is the treatment of choice for 7–10 days.

·     There is no reliably effective alternative for patients with sulfonamide allergy; consultation with an infectious diseases specialist is recommended. 

Prevention

·     Most U.S. outbreaks are linked to fresh imported produce, including cilantro, basil, raspberries, leafy greens, and salad mixes. Apparently, iceberg lettuce may be the culprit in this outbreak.

·     Washing produce helps reduce contamination but does not reliably eliminate Cyclospora, because oocysts adhere tightly to produce.

The people who should be most cautious include:

·     Infants and young children, who can become dehydrated more quickly.

·     Adults over age 65.

·     People with weakened immune systems, including transplant recipients, those receiving chemotherapy, advanced HIV infection, or high-dose immunosuppressive medications.

·     Individuals with chronic illnesses that make dehydration more hazardous, such as significant kidney disease or frailty.

Dr. M

AAP Red Book

CDC