Snapshot
Cyclospora cayetanensis — coccidian protozoan parasite causing prolonged watery diarrhea with profound fatigue and anorexia. Spread by fecally contaminated fresh produce & water (not person-to-person; oocysts need days–weeks in the environment to become infectious). Peaks May–August in the US; often linked to imported basil, cilantro, raspberries, snow peas, bagged salads, blackberries. Treat with TMP-SMX; illness can relapse and last weeks if untreated.
Recognition
- Parasite: Cyclospora cayetanensis — obligate intracellular apicomplexan (family Eimeriidae). Oocysts 8–10 μm, spherical, autofluorescent blue under UV; must sporulate outside host (1–2+ weeks) → NOT directly transmitted person-to-person
- Life cycle: Ingested sporulated oocysts → excyst in small bowel → invade jejunal enterocytes → asexual (merogony) and sexual (gametogony) stages → unsporulated oocysts excreted in stool
- Epidemiology (US): ~2,000–3,000+ reported cases/yr with large produce-linked outbreaks (CDC seasonal surveillance May–Aug). Endemic in Peru, Guatemala, Haiti, Nepal, Mexico, SE Asia — think travel exposure year-round
- Incubation: ~1 week (range 2–14 days) after ingestion
- Symptoms: watery non-bloody diarrhea (often explosive, 6–10 BM/day), profound fatigue & anorexia, weight loss (often 5–10 lb), cramping abdominal pain, nausea, low-grade fever, flatulence, bloating, myalgias
- Course: relapsing / remitting pattern; untreated illness lasts 10–12 weeks on average with cyclical “better then worse” waves. Immunocompromised patients (HIV/AIDS, transplant) → more severe, protracted, may develop biliary disease (acalculous cholecystitis)
- Red-flag mimics to consider: giardiasis, cryptosporidiosis, cystoisosporiasis, microsporidiosis, tropical sprue, celiac, C. difficile, viral gastroenteritis, IBD flare
Management
When to test
- Watery diarrhea > 7 days (esp. with fatigue / anorexia disproportionate to volume loss)
- Relapsing GI illness after travel to endemic region (Central/South America, Mexico, SE Asia, Nepal, Haiti) within the last 2–8 weeks
- Cluster of cases or exposure to fresh produce outbreak (basil, cilantro, raspberries, blackberries, snow peas, bagged salad, mesclun)
- Immunocompromised host with prolonged diarrhea
- Public-health rule: Cyclosporiasis is nationally notifiable in the US — report confirmed cases to your local health department
How & where to test
- Preferred (ED): multiplex stool GI PCR panel (BioFire FilmArray GI, Luminex xTAG, BD Max EBP) — Cyclospora is included on most panels; results in hours; highest sensitivity
- Ova & parasite (O&P) exam is NOT reliable for Cyclospora — must specifically request “stool for Cyclospora” which triggers modified acid-fast (Kinyoun) or safranin stain, or UV autofluorescence microscopy
- Order ≥ 3 stool specimens on separate days if using microscopy — oocyst shedding is intermittent
- Adjunct labs: CBC (may see mild eosinophilia — uncommon), BMP (dehydration, AKI), LFTs (esp. if RUQ pain — biliary involvement in AIDS), lactate if toxic-appearing
- Consider co-testing: Giardia / Crypto antigen or PCR, C. difficile PCR, HIV screen if unknown status, stool culture only if bloody/inflammatory features
- Where: hospital lab (send-out) or state / CDC reference lab for confirmation of outbreak strains (CDC DPDx accepts referrals)
Quick testing checklist — specimens & timing
☐ Test Specimen & container Volume Timing / # samples TAT ☐ Stool multiplex GI PCR (preferred — BioFire, Luminex xTAG, BD Max EBP) Loose/liquid stool in Cary-Blair transport vial (or lab-specified PCR collection kit) ≥ 1 g or fill to line 1 sample — send during active diarrhea; refrigerate if delay > 1 h 1–6 h ☐ Stool for Cyclospora (modified acid-fast / safranin / UV autofluorescence) — order explicitly, NOT covered by routine O&P Fresh stool in 10% formalin AND PVA (2-vial O&P kit) — write "Cyclospora / Cystoisospora" on the requisition 2–5 mL / half vial each ≥ 3 specimens on separate days (shedding is intermittent) — collect over 3–7 d 1–3 d ☐ Routine O&P (co-test to catch Giardia, Entamoeba, etc.) Same formalin + PVA vials Half vial each 3 specimens over 7–10 d 1–3 d ☐ Giardia / Cryptosporidium antigen (EIA / DFA) — if GI PCR unavailable Fresh stool, refrigerated (no fixative for antigen) 2 mL 1 sample; refrigerate ≤ 72 h 4–24 h ☐ C. difficile NAAT/PCR (if recent abx or healthcare exposure) Fresh unformed stool, sterile cup, refrigerate ≥ 2 mL 1 unformed sample; do not repeat for test-of-cure 2–6 h ☐ Stool culture (bacterial) — only if bloody / inflammatory features or fever Cary-Blair transport ≥ 1 g 1 sample 48–72 h ☐ BMP (hydration, K⁺, HCO₃, Cr / AKI) & lactate if ill-appearing Green-top (Li-hep) / gold SST; gray-top (Na-fluoride) for lactate 3–4 mL On arrival; repeat after resus if abnormal 30–60 min ☐ CBC (mild eosinophilia possible — uncommon) Lavender (EDTA) 3 mL On arrival 30–60 min ☐ LFTs + lipase if RUQ pain (rule out AIDS cholangiopathy / acalculous cholecystitis) Gold SST 4 mL On arrival 30–60 min ☐ HIV 4th-gen Ag/Ab if status unknown or immunosuppression suspected Gold SST 4 mL Once 1–2 h ☐ Pregnancy (β-hCG) for all reproductive-age females — changes antibiotic choice Urine or serum 10 mL urine / 3 mL blood On arrival 15–60 min ☐ Public-health notification — nationally notifiable disease Local/state health dept report form — On any positive result (or high-suspicion cluster) — do not wait for confirmation in outbreak — - Collection tips: collect during active diarrhea (highest oocyst yield); avoid urine or toilet-water contamination; refrigerate (2–8 °C) if transport > 1 h and no fixative used; formalin/PVA vials are stable at room temp for days.
- Common miss: ordering a routine O&P without specifying "Cyclospora" — lab will run trichrome, which does not stain the parasite. Always write "Cyclospora / Cystoisospora — modified acid-fast" on the requisition, or use a multiplex GI PCR that lists Cyclospora on its panel.
First-line treatment
- DS (160/800 mg) 1 tab PO BID × 7–10 days — immunocompetent adults
- Pediatric: 5 mg/kg TMP + 25 mg/kg SMX PO BID × 7–10 days (max adult dose)
- HIV/AIDS or immunocompromised: TMP-SMX DS 1 tab PO QID × 10 days, then secondary prophylaxis DS 1 tab PO 3×/wk (or daily) until CD4 > 200 for > 3 months
- Onset of benefit: symptoms improve within 1–3 days on TMP-SMX; failure to improve → recheck diagnosis / adherence
Alternatives (sulfa allergy / intolerance)
- 500 mg PO BID × 7 days
- — less effective than TMP-SMX; consider only if true sulfa allergy or contraindication
- Nitazoxanide 500 mg PO BID × 3 days (adult); pediatric 100 mg (1–3 y) or 200 mg (4–11 y) PO BID × 3 d
- — limited data, reasonable alternative especially in children; consider extending course in immunocompromised
- No proven role: metronidazole, tinidazole, azithromycin, doxycycline, paromomycin (do NOT use for Cyclospora)
- Pregnancy: TMP-SMX avoid in 1st trimester & near term (kernicterus) — consider nitazoxanide (Cat B) after risk-benefit discussion + ID/OB consult
Dosing & duration table
Population Drug Dose Route / Freq Duration Adult, immunocompetent TMP-SMX DS (160/800 mg) — 1st line 1 DS tab (160/800 mg) PO BID 7–10 days Pediatric (≥ 2 mo), immunocompetent TMP-SMX suspension 5 mg/kg TMP + 25 mg/kg SMX (max 160/800 mg per dose) PO BID 7–10 days HIV/AIDS or immunocompromised TMP-SMX DS (acute) 1 DS tab (160/800 mg) PO QID 10 days HIV/AIDS — 2° prophylaxis TMP-SMX DS 1 DS tab PO 3×/wk (or daily) Until CD4 > 200 × 3 mo Sulfa allergy — adult Ciprofloxacin (alt, less effective) 500 mg PO BID 7 days Alt / peds ≥ 1 y — adult Nitazoxanide 500 mg PO BID with food 3 days (extend if immunocompromised) Nitazoxanide — peds 4–11 y Nitazoxanide susp 200 mg (10 mL) PO BID with food 3 days Nitazoxanide — peds 1–3 y Nitazoxanide susp 100 mg (5 mL) PO BID with food 3 days Pregnancy (after 1st tri, not near term) TMP-SMX DS (with folate) or Nitazoxanide (Cat B) DS 1 tab / 500 mg PO BID 7–10 d / 3 d — ID + OB consult - Do NOT use metronidazole, tinidazole, azithromycin, doxycycline, or paromomycin — no efficacy vs Cyclospora. Symptoms should improve in 1–3 days on TMP-SMX; if not, recheck diagnosis, adherence, and immune status.
Acute ED management
- 1. Assess hydration & hemodynamics: orthostatics, mucous membranes, cap refill, UOP; check BMP + lactate if ill-appearing
- 2. IV fluids: LR or NS 500 mL–2 L boluses titrated to perfusion; oral rehydration solution (ORS) for tolerant patients — most cases manage as outpatient
- 4 mg IV/ODT for nausea
- 3. Antimotility: loperamide 4 mg PO then 2 mg after each loose stool (max 16 mg/day) — acceptable in non-bloody, non-toxic adults as adjunct; avoid in children < 6 y, dysentery, or suspected C. diff
- 4. Empiric antiparasitic: If clinical + exposure story strongly fits (prolonged watery diarrhea, endemic travel, produce outbreak) → start TMP-SMX DS BID × 7–10 days while stool PCR pending. Do NOT wait for confirmation in high-suspicion cases
- 5. Reportable disease: notify public health / infection prevention on positive test — supports outbreak tracking
- 6. Discharge counseling: hand hygiene, avoid food prep for others while symptomatic, drink safe water, wash produce (does NOT reliably remove oocysts — cooking is more protective), return precautions
ED disposition — admit vs discharge
- Admit
- Severe dehydration not corrected by ED resus, AKI, or significant electrolyte derangement (↓ K, ↓ HCO₃, ↑ Cr)
- Persistent inability to tolerate PO for hydration and TMP-SMX
- Immunocompromised (HIV/AIDS w/ CD4 < 200, transplant, chemo, high-dose steroids) with systemic illness, protracted course, or biliary involvement
- Suspected acalculous cholecystitis / AIDS cholangiopathy (RUQ pain, ↑ AlkP/bili) — needs imaging + surgery/GI
- Pregnancy with significant volume depletion or intractable emesis
- Infants, frail elderly, or hemodynamic instability / sepsis physiology
- Toxic appearance or diagnostic uncertainty requiring inpatient workup
- No safe outpatient follow-up or unreliable ability to fill/take antibiotics
Discharge- Hemodynamically stable, normal or corrected vitals after ED rehydration
- Tolerating PO fluids and first antibiotic dose in the ED
- Normal or near-normal BMP (no AKI, K > 3.3, HCO₃ > 18), no lactate elevation
- Immunocompetent, non-pregnant, no biliary symptoms
- Reliable outpatient follow-up (PCP or ID) within 48–72 h, able to obtain TMP-SMX (or alternative) prescription
- Reviewed return precautions and food-safety / hygiene counseling
Return precautions (give to every discharged patient)
- Return to the ED immediately for: lightheadedness or fainting, inability to keep any fluids down for > 8–12 h, no urine output for > 8 h, dry mouth with sunken eyes, confusion or extreme weakness
- Return for: bloody or black stools, severe or worsening abdominal pain, RUQ pain with yellowing of skin/eyes (possible biliary involvement), fever > 102 °F (39 °C) or shaking chills
- Return if: symptoms are not improving within 3 days of starting TMP-SMX, or symptoms relapse after initial improvement (common with Cyclospora — may need re-treatment)
- Pregnancy: return for decreased fetal movement, vaginal bleeding, contractions, or any concern for dehydration
- Children: return for < 3 wet diapers in 24 h, no tears when crying, sunken fontanelle, lethargy, or persistent vomiting
- Home care: take full antibiotic course (do not stop early — high relapse rate), sip ORS / electrolyte fluids frequently, bland diet as tolerated, rest
- Prevent spread & reinfection: thorough handwashing after toilet and before food prep; do not prepare food for others while symptomatic; wash produce (cooking is more reliable — oocysts resist rinsing); drink bottled/boiled/filtered water if traveling
- Follow-up: PCP or ID within 48–72 h; public health may contact patient for outbreak investigation (reportable disease)
Pearls / pitfalls
- Think Cyclospora when diarrhea > 1 week is dominated by fatigue and anorexia out of proportion to stool volume, especially May–August or after travel
- Standard O&P misses it — you must specifically request Cyclospora testing or use a multiplex GI PCR
- Not contagious person-to-person — oocysts need environmental sporulation. Reassure households; focus on food/water source
- TMP-SMX is the only proven therapy; quinolones and nitazoxanide are backups with weaker evidence
- Relapse is common if course is truncated — complete full 7–10 days and confirm resolution
- Public health matters — early reporting has stopped multi-state produce outbreaks. Notify your health department
- Wash ≠ safe — oocysts are sticky and rinse-resistant; cooking is the reliable kill step for high-risk produce
Educational aid only — verify against local antibiogram, CDC guidance, and current IDSA/CDC treatment recommendations.