Cyclosporiasis-Updates on Clinical Presentation, Pathology, Clinical Diagnosis, and Treatment

Abstract

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. This manuscript reviews important aspects of the biology, epidemiology, and clinical manifestations of C. cayetanensis and provides an in-depth discussion of current laboratory diagnostic methods.

Keywords: Cyclospora; diagnostics; diarrhea; parasite; parasitic; pathology; protozoan.

Figure 1

Life cycle of Cyclospora cayetanensis. Unsporulated, non-infective oocysts are passed in the feces (1). In the environment (2), sporulation occurs after days or weeks at temperatures between 22 °C to 32 °C, resulting in the division of the sporont into two sporocysts, each containing two elongated sporozoites (3). The sporulated oocysts can contaminate fresh produce and water (4) images, which are then ingested (5). The oocysts excyst in the gastrointestinal tract, freeing the sporozoites, which invade the epithelial cells of the small intestine (6). Inside the cells, they undergo asexual multiplication into Type I and Type II meronts. Merozoites from Type I meronts perpetuate the asexual cycle, while merozoites from Type II meronts undergo sexual development into macrogametocytes and microgametocytes upon invasion of another host cell. Fertilization occurs, and the zygote develops to an oocyst, which is released from the host cell and shed in the stool (7). Figure courtesy of the CDC-DPDx.

Figure 2

Oocysts of Cyclospora cayetanensis in stool specimens observed under different staining methods. (A) unstained concentrated wet mount. (B) UV autofluorescence. (C) differential interference contrast (DIC). (D) trichrome stain. (E) Kinyoun’s modified acid-fast. (F) modified safranin. (Figures courtesy of the CDC-DPDx).

Figure 3

Small intestinal biopsy showing villous blunting and increased chronic inflammatory cells within the lamina propria (hematoxylin and eosin stain, 100x magnification). Higher power (inset, 1000×) shows intracellular Cyclospora cayetanensis parasites including a Type II meront containing 4 merozoites (arrow). Each merozoite shown here measures approximately 3–4 micrometers.