A taxonomic re-appraisal of Sarcocystis nesbitti (Protozoa: Sarcocystidae) from the monkey Macaca fascicularis in Yunnan, PR China.

The first detection of Sarcocystis nesbitti Mandour, 1969 in the Chinese mainland is reported and the morphology of the sarcocyst is described in detail. The parasite was detected in the monkey, Macaca fascicularis, maintained on a monkey farm in Yunnan Province; the infection may have occurred via faecal contamination from local rats, mice and/or birds. S. nesbitti was characterized as follows: a macroscopic sarcocyst, length of the cyst up to 2 mm; cyst wall smooth, thin and no perpendicular protrusion is seen under the light microscope; border of cyst wall wavy, primary cyst wall thin (38-65 nm) and invaginated; ground substance about 0.5-0.76 microm thick with electron-dense granules and concentric spherical bodies. The cyst wall is described as type 1 by electron microscopy. It is suspected that S. nesbitti may utilize Macaca mulatta, M. fascicularis, Cercocebus atys, and Papio papionis, as well as human as intermediate hosts. The taxonomy of S. nesbitti is re-appraised in the light of a consideration of possible experimental artefacts and examination of the past literature. Evidence is presented that S. nesbitti may be one of the species infecting humans in South Asia and that the monkey may be a potential reservoir host.

Characterization of Sarcocystis species in domestic animals using a PCR-RFLP analysis of variation in the 18S rRNA gene: a cost-effective and simple technique for routine species identification.

Thirteen restriction endonucleases were used to investigate nuclotide sequence variation in the 18S rRNA DNA of 88 individuals from ten Sarcocystis taxa collected as cysts from their intermediate hosts, swine, cattle and water buffalo. A DNA sequence of approximately 900 bp was used. A total of 26 electromorphs were detected. The electromorphs were sorted into seven different haplotypes that coincided with the six named species and an unidentified species from cattle. These findings support those of our morphological examinations, which suggested that the taxa resembling Sarcocystis hirsuta, S. hominis, both found in water buffalo, and S. sinensis found in cattle, are not new species but are in fact S. hirsuta and S. hominis as found in cattle, and S. sinensis as found in water buffalo; this finding supports the idea that these species can utilize both cattle and water buffalo as intermediate hosts and are not restricted to one or the other host group as previously thought. PCR-RFLP resolved by agarose gel electrophoresis is shown to be an easy and rapid method of discriminating between these species.