Transmission electron microscopy on a case of Cyclospora cayetanensis infection from an immune-competent case confirms and extends prior detailed descriptions of its notably small endogenous stage

Authors: Dubey, Jitender; CHARLESWORTH, JON - Mayo Clinic; PRITT, BOBBI - Mayo Clinic

Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2022
Publication Date: 6/8/2022
Citation: Dubey, J.P., Charlesworth, J., Pritt, B. 2022. Transmission electron microscopy on a case of Cyclospora cayetanensis infection from an immune-competent case confirms and extends prior detailed descriptions of its notably small endogenous stage. Parasitology. 149:1397-1405. https://doi.org/10.1017/S0031182022000786.
DOI: https://doi.org/10.1017/S0031182022000786

Interpretive Summary: Coccidia are single celled parasites of medical and veterinary importance. Economically and clinically Important genera include Eimeria, Cryptosporidium, Toxoplasma, Sarcocystis, Cystoisospora, and Cyclospora. Cyclosporosis is an emerging problem worldwide and the disease is caused by Cyclospora cayetanensis. It is fecally transmitted infection. Humans are the only known hosts for C. cayetanensis. Lack of experimental animal models and inability to cultivate the parasite in vitro hampers progress on its risk assessment and to estimate environmental contamination. Accurate diagnosis based on histology of biopsy specimens is difficult because of small size of the parasite. Here, the authors provide accurate description of life cycle stages of C. cayetanensis in small intestinal biopsy of a human patient by electron microscopy. This paper will be of interest to biologists, parasitologists and pathologists.

Technical Abstract: Although infections with Cyclospora cayetanensis are prevalent worldwide, many aspects of this parasite’s life cycle remain unknown. Humans are the only known hosts of this parasite. Existing information on its endogenous development has been derived from histological examination of only a few biopsy specimens. In histological sections, its stages are less than 10 µm, making definitive identification difficult. Here, confirmation of cyclosporiasis in a duodenal biopsy specimen from an 80- year- old man without any recognized immunodeficiency patient is reported. Asexual forms (schizonts) and sexual forms (gamonts) were located in enterocytes, including immature and mature schizonts, an immature male gamont, and a female gamont. Merozoites were small (<5 µm x 1 um) and contained 2 rhoptries, subterminal nucleus, and numerous micronemes and amylopectin granules. These parasite stages were like those recently reported in the gallbladder of an immunocompromised patient, and thus suggest that the general life cycle stages are not altered by immunosuppression.