MOLECULAR SYSTEMATICS AND COMPARATIVE POPULATION GENETICS OF PARASITIC ORGANISMS THAT THREATEN FOOD SAFETY AND SECURITY
Title: Phylogenetic analysis of of Sarcocystis nesbitti (Coccidia: Sarcocystidae) suggests a snake as its probable definitive host
Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 22, 2011
Publication Date: February 10, 2012
Citation: Tian, M., Chen, Y., Rosenthal, B.M., Liu, X., He, Y., Dunams, D.B., Cui, L., Yang, Z. 2012. Phylogenetic analysis of of Sarcocystis nesbitti (Coccidia: Sarcocystidae) suggests a snake as its probable definitive host. Veterinary Parasitology. 183:373-376.
Interpretive Summary: Parasites recognized as belonging to the genus Sarcocystis were identified in macaques, but their relationship to similar parasites in other primates (and human beings) was unknown. Equally unclear was the likely definitive host who might have served as the source for primate exposure.
Small subunit rDNA were sequenced from each of two such cysts, found those sequences to be identical to each other, and discovered that they are specifically related to a group of parasites from Asia which complete their life-cycle in carnivorous snakes. This allows us to understand the parasite as very different from others known to infect people, and provides a basis for suspecting a snake as the natural definitive host of this parasite.
This research will guide parasitologists, wildlife biologists, and epidemiologists in establishing evidence for or against the idea that snakes excrete a parasitic form that is infectious for macaques, and probably other primates.
Sarcocystis nesbitti was first described by Mandour in 1969 from rhesus monkey muscle. Its definitive host remains unknown. 18SrRNA gene of Sarcocystis nesbitti was amplified, sequenced, and subjected to phylogenetic analysis. Among those congeners available for comparison, it shares closest affinity with those species of Sarcocystis which use snakes as definitive hosts. We therefore hypothesize that a snake may serve as the definitive host for S. nesbitti.