SARCOSPORIDIASIS IN RODENTS FROM THAILAND

One to six Sarcocystis spp. were identified in the skeletal muscles of 41 (33%) of 124 wild rodents (Rattus spp and Bandicota indica) mainly captured in the central plains of Thailand throughout the year in 199 5. Included were S. singaporensis, S. villivillosi, and S. murinotechi s-like cysts all of which showed a striated cyst wall at the light mic roscopical level, and Sarcocystis cymruensis, S. sulawesiensis, and S. zamani which possessed smooth cyst walls. The ultrastructure of the c yst wall and other morphological characteristics used to distinguish s pecies are described. By inoculation of muscle cysts from wild-caught rodents into coccidia-free pythons (Python reticulatus, P. molurus biv ittatus), we confirmed that P. reticulatus is a suitable definitive ho st for S. singaporensis and S. zamani in Thailand. Furthermore, we sho wed by fecal examination of reticulated pythons collected in the wild and subsequent experimental infection of laboratory rats that these ho sts also are naturally infected with both species. Sarcocystis cymruen sis is reported for the first time from Southeast Asia. This parasite was prevalent in brown rats (Rattus norvegicus) and bandicoot rats (B. indica) which were captured near human habitations; it is likely to b e transmitted to rats via cats. The definitive hosts of S. sulawesiens is and S. murinotechis are unknown. Hence, at least three Sarcocystis spp. (S. singaporensis, S. zamani, S. villivillosi) are likely to cycl e between snakes and rodents in agricultural areas in Thailand. Among these, S. singaporensis appears to be the most prevalent species.