Location: Animal Parasitic Diseases LaboratoryTitle: Sarcocystis pantherophis, n. sp. from eastern rat snakes (Pantherophis alleghaniensis) definitive hosts and interferongamma gene knockout mice as experimental intermediate hosts
|VERMA, SHIV - Non ARS Employee|
|LINDSAY, DAVID - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)|
Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2017
Publication Date: 10/1/2017
Citation: Verma, S., Lindsay, D., Mowery, J.D., Rosenthal, B.M., Dubey, J.P. 2017. Sarcocystis pantherophis, n. sp. from eastern rat snakes (Pantherophis alleghaniensis) definitive hosts and interferongamma gene knockout mice as experimental intermediate hosts. Journal of Parasitology. 103:547-554.
Interpretive Summary: Toxoplasma and Sarcocystis are related single celled parasites of livestock and humans. While Toxoplasma has long been recognized to cause neurologic disease in many warm blooded hosts, including humans, recently a mysterious illness has been reported in humans that had a history of travel to Malaysian region. These patients had symptoms simulating toxoplasmosis. Results for toxoplasmosis testing were negative and Sarcocystis parasite was found in muscle biopsies of some of these patients. Epidemiological data suggested a link to ingestion of food and water contaminated with Sarcocystis (sporocysts) excreted in feces of snakes. Nothing is known of Sarcocystis infection in snakes in the USA. The authors report Sarcocystis parasites in feces of rat snakes (Pantherophis alleghaniensis). Molecularly, the parasite in rat snake has similarities to parasites in snakes in Malaysia. Feeding of these snake parasites induced a neurological illness in mice. The results will be of interest to biologists, and parasitologists.
Technical Abstract: Here we report a new species, Sarcocystis pantherophisi with the Eastern rat snake (Pantherophis alleghaniensis) as natural definitive host and the interferon gamma gene knockout (KO) mouse as the experimental intermediate host. Sporocysts (n=15) from intestinal contents of the snake were 17.3 x 10.9 µm. Sporocysts were orally infective to KO mice but not to laboratory raised albino outbred house mice (Mus musculus). The KO mice developed schizont-associated neurological signs and schizonts were cultivated in vitro from the brain. Mature sarcocysts were found in skeletal muscles of KO mice examined 41 days post inoculation (PI). Sarcocysts were slender, up to 70 im wide and up to 3.5 mm long. By light microscopy, sarcocysts appeared thin-walled (<1 µm) without projections. By transmission electron microscopy, the sarcocyst wall was a variant of “type 1” (type 1i, new designation). The parasitophorous vacuolar membrane (pvm) had approximately 100 nm wide x 100 nm long bleb-like evaginations interspersed with 100 nm wide x 650 nm long elongated protrusions at irregular distances, and invaginations into the ground substance layer (gs). The gs was smooth with a maximum thickness of 500 nm. Longitudinally cut bradyzoites at 54 days PI were banana-shaped, 7.8 x 2.2 im (n=5) in size. Molecular characterization using 18S rRNA, 28S rRNA, ITS-1, and cox1 genes revealed a close relationship with other Sarcocystis parasites that have snake-rodent life cycles. The parasite in the present study was molecularly, and biologically similar to a previously reported isolate (designated earlier as Sarcocystis sp. ex Pantherophis alleghaniensis) from P. alleghaniensis, and was structurally different from other Sarcocystis species so far described.