Cyclosporiasis

There has been a well-publicized outbreak of cyclosporiasis, a gastrointestinal infection characterized by profuse watery diarrhea, contracted by consuming contaminated produce. The largest current outbreak has been traced to shredded lettuce imported from a Mexican farm and distributed over 5 Midwestern states through Taco Bell but it has been an under diagnosed and undertreated illness of which we should all be aware and against which we should continue precautions going forward. 

Cyclospora is a tiny single celled parasite endemic to tropical and subtropical regions with a seasonal variation peaking in summer. Once present in fecally contaminated waters, it is ingested by the human host and embeds itself in the small intestine and generally requires a one to two week incubation period before symptoms. This delay compounds the difficulty of identifying sources. Symptoms include watery diarrhea, often explosive, as well as nausea, vomiting, cramping, bloating, poor appetite and fatigue, though it can also be asymptomatic. Complications are infrequent and rarely life threatening, with malabsorption, cholecystitis and reactive arthritis reported. Duration ranges from days to months. All ages are at risk. 

Because cyclospora is excreted in a clinically inactive form called an oocyte, it requires an additional one to two week period outside the host in a favorable hot and humid environment to mature (sporulate) and become infectious, so direct person to person transmission is unlikely. Travelers to endemic areas are at particular risk, but most United States cases are due to ingesting contaminated produce including but not limited to lettuce, basil, cilantro, raspberries and snow peas. Prevention starts with awareness, including precautions about water and food sources when traveling to endemic areas. At home fresh produce should be thoroughly washed and scrubbed, and hands washed after handling. Heating to 158°F will kill cyclospora.

Diagnosis can be problematic. Routine stool tests can miss the organism due to intermittent shedding, small size, and need for special stains and multiple samples. DNA/ PCR (polymerase chain reaction) testing is more accurate but often not included in panels unless specifically requested. Most episodes are undiagnosed and resolve with supportive treatment including vigorous hydration but risk a prolonged course. Diagnosis is important, because cyclosporiasis responds to a common antibiotic not usually used for diarrheal illness, trimethoprim- sulfamethoxazole (Bactrim). Other antibiotics are generally ineffective. Treatment for sulfa allergic, pregnant, nursing and very young individuals must be determined with one's health providers. There is no vaccine. CDC and Massachusetts DPH websites were resourced in preparing this report.