Re-evaluation of merogony of a Cystoisospora ohioensis-like coccidian and its distinction from gametogony in the intestine of a naturally infected dog

Authors: Dubey, Jitender

Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2018
Publication Date: 2/6/2019
Citation: Dubey, J.P. 2019. Re-evaluation of merogony of a Cystoisospora ohioensis-like coccidian and its distinction from gametogony in the intestine of a naturally infected dog. Parasitology. 146:740-745. https://doi.org/101017/S0031182018002202
DOI: https://doi.org/10.1017/S0031182018002202

Interpretive Summary: Toxoplasma, Neospora, Sarcocystis, and Cystoisopora are related coccidian parasites that cause severe illness in livestock and companion animals. Oocyst is the environmentally resistant stage passed in feces of the definitive hosts. While Toxoplasma and Neospora have wide host range, Cystoisospora are more host specific. Cystoisospora ohioensis is a pathogenic coccidian of dogs with many aberrant/paratenic hosts. Its life cycle is not fully known. Here, the author describes asexual cycle (meronts,schizonts) and sexual cycle of C. ohioensis like organism in the intestine of a naturally infected dog.. These results will be of interest to parasitologists and veterinarians in diagnosis of coccidiosis in dogs.

Technical Abstract: Four species of Cystoisospora, C. canis, C. ohioensis, C. neorivolta, and C. burrowsi are described from feces of dogs. Of these, the oocysts of C. canis are the largest and easily distinguished from the remaining 3 species. Oocysts of C. ohioensis, C. neorivolta, and C. burrowsi are difficult to distinguish because of overlap in their sizes. However, based on endogenous developmental stages, C. ohioensis is distinct from C. neorivolta and C. burrowsi because its endogenous stages are confined to surface epithelium of intestine whereas endogenous stages of C. neorivolta and C. burrowsi are predominantly in the lamina propria. There are uncertainties regarding the endogenous stages of C. neorivolta and C. burrowsi and there is no way now to determine whether C. burrowsi and C. neorivolta are different parasites; therefore, these are referred as C. ohioensis-like organisms. Additionally, mode of division of asexual stages of coccidia of dogs is largely unknown and ultrastructural studies are lacking. In the present study, development of asexual and sexual stages of a C. ohioensis-like organism in a naturally infected dog is described by light microscopy and by transmission electron microscopy. Merozoites divided by endodyogeny/merogony. Meronts were merozoite-shaped and contained a maximum of 8 nuclei. A distinctive feature of merozoites was the presence of many PAS-positive amylopectin granules that were absent or rare in immature microgamonts making it possible to distinguish them.