Location: Animal Parasitic Diseases
Title: Experimental transmission of Sarcocystis muris (Apicomplexa): Sarcocystidae from the feces of a naturally infected feral cat (Felis catus) to immunocompetent and immunocompromised mice Authors
Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 11, 2013
Publication Date: N/A
Interpretive Summary: Toxoplasma and Sarcocystis are genera of single celled parasites of livestock and humans. Cats act as transmitting agents (definitive hosts) for some species of these parasites. Cats become infected by eating infected tissues carrying these parasites and the livestock and humans become infected by ingesting food and water contaminated by cat feces containing environmentally resistant stages. The authors found for the first time Sarcocystis muris paradsite in the feces of a naturally infected cat for the first time. These results will be of interest to parasitologists and biologists.
Technical Abstract: Cats serve as definitive hosts for zoonotic toxoplasmosis, a prevalent infection that threatens human reproductive health, but they also excrete sporocysts of related parasites that pose no known human health risk. Here, we provide the first definitive evidence for natural infection with Sarcocystis muris, one such enzootic parasite. Sporulated Sarcocystis sp. sporocysts were found in rectal contents of an adult feral cat (Felis catus) in Giza, Egypt. After orally inoculating these into 2 Swiss Webster mice, sarcocysts were found to have developed in skeletal muscles 114 days later. By transmission electron microscopy, the cyst wall corresponded to Type 1, and the parasitophorous vacuolar membrane had tiny out pocketing of blebs (<200 nm thick) that were not invaginated into the interior of the cyst; these structures were identical to sarcocyst wall described for a Costa Rican isolate of S. muris that has served as an experimental model for nearly four decades. Two parasite-free cats fed sarcocysts infected muscles developed patent infections; fully sporulated sporocysts (10-11x 7.0 um) were found in the lamina propria of small intestines of cats killed 6 and 7 days post-inoculation (PI). Interferon gamma gene knockout (KO) mice were orally inoculated with sporocysts from experimentally-infected cats, and their tissues were examined histologically; sarcocysts were found in 5 KO mice killed 87,115,196,196,196 days PI but, no stages were seen in 5 KO mice 10,14,14,18, and 39 days PI. Bradyzoites were released from intramuscular sarcocysts of a KO mice killed 115 days PI and orally inoculated in to 5 KO mice. No stage of Sarcocystis was found in any organ (including intestinal lamina properia) of KO mice killed 4, 8, 81, 190, and 190 day PI, confirming that the definitive host is required to complete the lifecycle even in the case of immunodeficient mice. This is the first confirmation of Sarcocystis muris infection in a naturally-infected cat anywhere.