Cyclospora cayetanensis infection in humans: biological characteristics, clinical features, epidemiology, detection method and treatment

Abstract

Cyclospora cayetanensis, a coccidian parasite that causes protracted and relapsing gastroenteritis, has a short recorded history. At least 54 countries have documented C. cayetanensis infections and 13 of them have recorded cyclosporiasis outbreaks. Cyclospora cayetanensis infections are commonly reported in developing countries with low-socioeconomic levels or in endemic areas, although large outbreaks have also been documented in developed countries. The overall C. cayetanensis prevalence in humans worldwide is 3.55%. Among susceptible populations, the highest prevalence has been documented in immunocompetent individuals with diarrhea. Infections are markedly seasonal, occurring in the rainy season or summer. Cyclospora cayetanensis or Cyclospora-like organisms have also been detected in food, water, soil and some other animals. Detection methods based on oocyst morphology, staining and molecular testing have been developed. Treatment with trimethoprim-sulfamethoxazole (TMP-SMX) effectively cures C. cayetanensis infection, whereas ciprofloxacin is less effective than TMP-SMX, but is suitable for patients who cannot tolerate co-trimoxazole. Here, we review the biological characteristics, clinical features, epidemiology, detection methods and treatment of C. cayetanensis in humans, and assess some risk factors for infection with this pathogen.

Keywords: Biological characteristic; Cyclospora cayetanensis; clinical feature; detection method; epidemiology; treatment.

Fig. 1.

Morphology of C. cayetanensis oocysts under microscopy. Oocysts in stool smears stained with modified acid-fast stain under light microscopy; two oocysts are stained with different intensities (A); differential interference contrast microscopy of wet mounts, a partially sporulated oocyst can be seen (B); epifluorescence microscopy with a 330–380 nm UV excitation filter (C).

Fig. 2.

Phylogenetic relationships of C. cayetanensis and other apicomplexan protozoa. Phylogeny inferred with a neighbour-joining analysis of small-subunit ribosomal RNA gene sequences (A) reported by Li et al. (2017); mitochondrial genomes (B) reported by Cinar et al. (2015) and apicoplast genomes (C) reported by Tang et al. (2015), based on distances calculated with the Kimura 2-parameter model. Bootstrap values >50% from 1000 replicates are shown at the nodes. Scale bars indicate estimated substitutions per site.

Fig. 3.

Number of documented human C. cayetanensis infections and prevalence worldwide. Number of documented infection cases (A) and prevalence (B) worldwide (95% confidence intervals are shown in brackets).