Submitted to: Parasitology International
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/13/2009
Publication Date: 3/29/2009
Publication URL: dx.doi.org/10.1016/j.parint.2009.03.004
Citation: Xiang, Z., Chen, X., Yang, L., Zhou, B., Jiang, R., Rosenthal, B.M., Lei, L., Luan, P., Liu, J., Attwood, S., Zuo, Y., Cui, L., Zhang, Y., Yang, Z. 2009. Non-invasive methods for identifyig oocysts of Sarcocystis spp. from definitive hosts. Parasitology International. 58(3):293-296. Interpretive Summary: Many animals, including livestock, contract coccidian infections when they ingest food, or imbibe water, contaminated with oocysts excreted by a carnivore. In only a handful of cases has the carnivore in question has been definitively established for a given parasite, leaving hundreds of others incompletely described. Here, diagnostic genetic features were employed to definitively diagnose the parasites excreted by dogs, cats, and people who were known to have consumed infectious meat. As expected, the genetic signature of each parasite was constant throughout its transmission. Certain improvements are illustrated for the purpose of isolating such oocysts, which should aid future efforts to better 'connect the dots' as such parasites alternate between predator and prey species. Ultimately, this approach will help better define risk factors for animal and public health.
Technical Abstract: Because the excreted sporocysts of various species of Sarcocystis may not be discriminated morphologically, we sought to validate a diagnostic technique based on variation in the 18S rDNA sequence. Oocysts of Sarcocystis hominis, Sarcocystis fusiformis and Sarcocystis cruzi were collected from the feces of their definitive hosts (human, cats, and dogs) using a new method employing filter paper. Corresponding samples were obtained from their intermediate hosts: cattle and water buffalo. These were then distinguished using a PCR-RFLP based method applied to a partial 18S rRNA gene (ssrRNA) sequence. This approach successfully distinguished among the three Sarcocystis taxa when sampled either as tissue cysts or oocysts. The same, unique restriction digestion pattern characterizes the tissue cysts and oocysts of each parasite taxon. The technique can detect 7 sporocysts (the equivalent of 3 and 1/2 oocysts) in fecal samples, making it a potentially useful tool in the identification of Sarcocyst species. To our knowledge, this represents the first report using molecular diagnostic procedures to diagnose oocysts of Sarcocystis in faecal samples.