Although the CDC seems to have identified a single supplier of lettuce to Taco Bell restaurants as the source of the Cyclospora infections that have sickened more than 1644 people in five states, gastroenterologists need to be vigilant for symptoms that may not occur for up to 2 weeks after exposure and be prepared to diagnose and treat these patients.

Gastroenterologist Tomás DaVee, MD, associate professor at McGovern Medical School at University of Texas Health Science Center at Houston, highlighted three key points:

1. Stay Aware

Cyclosporiasis is a foodborne diarrheal illness with a median incubation period of approximately 7 days with the potential for prolonged symptoms, so clinicians should maintain diagnostic vigilance rather than reassurance-only management.

The key clinical syndrome is persistent watery diarrhea, which can be waxing or waning, often accompanied by systemic and associated gastrointestinal (GI) symptoms such as fatigue, anorexia, nausea, abdominal cramping, dehydration, and weight loss. 

2. Test and Treat Appropriately

If patients have eaten lettuce from a suspicious or confirmed source and present with consistent symptoms, empiric treatment with trimethoprim-sulfamethoxazole in immunocompetent hosts may be considered.

For most patients with acute (< 1 week), nonbloody diarrhea (non-travel-associated), most experts recommend against giving empiric antibiotics. Empiric management of acute diarrhea starts with oral rehydration and nutrition maintenance.

Empiric antibiotics are favored when there is severe illness (fever ≥ 38.5 °C, hypovolemia, ≥ 6 unformed stools in 24 hours, severe abdominal pain); inflammatory diarrhea features (bloody diarrhea, small-volume mucous stools, fever), or high-risk host features (age ≥ 70 years, cardiac disease, immunocompromising condition, inflammatory bowel disease, pregnancy).

For undifferentiated acute diarrhea, suggested empiric treatments include azithromycin or a fluoroquinolone.

Within the parasitic differential, Cyclospora overlaps clinically with other protozoa such as Giardia, Cryptosporidium, and Cystoisospora, which can be distinguished by stool microscopy or polymerase chain reaction (PCR) test.

Accurate diagnosis requires the right test: stool microscopy can detect oocysts using modified acid-fast staining, safranin staining, or fluorescence microscopy. Oocysts should be distinguished from Cryptosporidium (smaller, ~5 μm vs Cyclospora ~8-10 μm). PCR assays are also available.

For persistent diarrhea (> 1 week), evaluation should include testing for parasitic organisms and considering noninfectious etiologies if no pathogen is found and symptoms worsen or become chronic.

If available, multiplex molecular stool panels can detect Cyclospora (eg, BioFire FilmArray GI panel; EasyScreen Gastrointestinal Parasite Detection Kit) and can facilitate earlier recognition than relying on stool microscopy alone. Because Cyclospora assays vary across brands, physicians must explicitly write “Test for Cyclospora” on laboratory requisitions rather than just ordering a generic “GI PCR Panel.”

If a multiplex molecular panel is not available, a laboratory must perform the special “modified acid-fast staining” or “UV fluorescence microscopy.” Sending three stool specimens on consecutive days (or separated by at least 24 hours) improves yield because of intermittent excretion.

3. Alert Patients

If patients are likely to have been exposed, targeted patient notifications through MyChart or similar portals may help identify cases earlier, encourage appropriate testing, and reduce diagnosis delays.

Patient messaging should advise individuals to seek medical evaluation if symptoms develop within 2-14 days after exposure and to mention the potential Cyclospora exposure as routine GI testing may not detect the parasite unless specifically requested.

Marilynn Larkin, MA, is an award-winning medical writer and editor based in New York City whose work has appeared in numerous publications, including Medscape Medical News and its sister publication MDedge, The Lancet (where she was a contributing editor), and Reuters Health.