Characterizarion of Sarcocystis spp.

MORÉ, G.; GONDIM, L. F. P.

Encuentro; Apicowplexa viertual meeting; 2021

Apicomplexan protozoan parasites from the genus Sarcocystis have heteroxenous life cycles, generally using herbivores as intermediate hosts and carnivores/omnivores as definitive hosts. Most Sarcocystis spp. are related to a predator-prey relationship. Sarcocystosis in intermediate hosts (IH) is generally asymptomatic and chronic, producing muscle cysts or sarcocysts containing banana-shaped bradyzoites. The definitive hosts (DH) become infected by ingestion of sarcocysts and usually show mild or no clinical signs. The gametogony and sporogony stages take place in small intestinal cells and the thin sporulated oocyst wall breakes, releasing the sporocysts, each containing 4 sporozoites and a residual body. More than 200 Sarcocystis spp. have been named and described, partially based on cyst morphology and life cycles. Humans are DH for S. hominis and S. suihominis with bovines and swine as IH, respectively. Humans can also act as IH, as muscular sarcocystosis has been reported in people traveling in Malaysia, presumably caused by S. nesbitti (snakes as DH). In addition, a digestive symptomatology has been reported as ?food poisoning? by ingestion of horse and South American camelids meat containing Sarcocystis spp. cysts. During the last years, morphological characterization established on ultrastructure of cyst walls and molecular identification of several new Sarcocystis species were performed, allowing improved descriptions and re-descriptions. The use of molecular tools, specially PCR and sequencing, is being increasingly used for Sarcocystis spp. diagnosis, which has attenuated the need for bioassays. The principal DNA targets are the rRNA genes (18S, 28S, 5.8S and ITS), mitochondrial gene Cox1, and some genes coding for surface antigens (SAGs), however, several species have no sequences deposited in public databases. This presentation is intended to summarize the last advances on Sarcocystis spp. characterization and diagnosis. Emphasis is given on zoonotic Sarcocystis spp. and those using cattle, swine and cervids as IH, and opossums, canids and snakes as DH.