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Cyclospora cayetanensis is an intestinal coccidian parasite transmitted to humans through the consumption of oocysts in fecally contaminated food and water. Infection is found worldwide and is highly endemic in tropical and subtropical regions with poor sanitation. Disease in developed countries is usually observed in travelers and in seasonal outbreaks associated with imported produce from endemic areas. Recently, summertime outbreaks in the United States have also been linked to locally grown produce. Cyclosporiasis causes a diarrheal illness which may be severe in infants, the elderly, and immunocompromised individuals. The increased adoption of highly sensitive molecular diagnostic tests, including commercially available multiplex panels for gastrointestinal pathogens, has facilitated the detection of infection and likely contributed to the increased reports of cases in developed countries.
Diagnostic Method | Advantages | Disadvantages |
---|---|---|
Stool Microscopy | ||
Direct wet mount | Fast, inexpensive; simultaneous detection of other intestinal parasites | Lack of sensitivity without concentration step; lack of defined morphologic features might make detection difficult for microscopists |
Concentrated wet mount | Fast, inexpensive; simultaneous detection of other intestinal parasites | Lack of defined morphologic features might make detection difficult for microscopists |
Differential Interference Contrast (DIC) | Increased sensitivity by highlighting internal structures | Not routinely available in many diagnostic labs |
Ultraviolet autofluorescence | More sensitive than permanent smears; simultaneous detection of other coccidian oocysts and several helminth eggs | Requires specific UV filters that may not be routinely present in diagnostic labs |
Lacto-phenol cotton blue | Fast, inexpensive; may be advantageous in resource-poor areas where acid-fast staining is not available | Non-specific; likely false positives with fungal elements |
Trichrome/iron hematoxylin stain | Simultaneous detection of other intestinal protozoans | Oocysts do not stain with trichrome |
Modified Ziehl-Neelsen (ZN) stain | Increased sensitivity over traditional O&P exams | Inconsistent staining of oocysts |
Kinyoun’s modified acid-fast (MAF) stain | Increased sensitivity over traditional O&P exams | Inconsistent staining of oocysts |
Modified safranin | More consistent staining of oocysts over ZN and MAF | Requires heating of stain |
Auramine O (auramine-phenol) | More sensitive than traditional O&P exams | May be less sensitive than MAF, ZN; requires fluorescent microscope |
Histopathology | ||
Hematoxylin-and-eosin (H&E), periodic acid Schiff (PAS) | Identify multiple developmental stages of C. cayetanensis | Not routinely ordered for C. cayetanensis; may be difficult to distinguish from Cystoisospora belli |
Ziehl–Neelsen stain, Fite’s acid-fast stain | Can detect oocysts in tissues | Pre-oocyst stages may not stain |