Morphologic characterization of Sarcocystis spp. histologically detected from the diaphragm and tongue of Rattus norvegicus and Rattus tanezumi

This study focused on the detection of Sarcocystis spp. in two species of rats, Rattus norvegicus and R. tanezumi collected from agricultural area in Dasmarinas, Cavite. This aimed to corroborate the presence of Sarcocystis spp. in different species of rats found in the agricultural area. Further the establishment of different Sarcocystis spp in Rattus spp. based on the parasite’s morphologic characterization is also emphasized. Sixty-nine rats (36 R. norvegicus and 33 R. tanezumi) were collected through trapping. Individual rodent autopsy for host identification was performed by determining the morphological differences and external measurements prior to dissection. Tissue samples were examined for the presence of white rice-grain sized nodules. Morphological characteristics of the cysts, particularly the size, shape, and presence of protrusions were noted. Statistical analysis using ANOVA for the significant difference on the number of infected rats per species and across muscle type was done at p≤0.05. Infection in R. tanezumi was higher (48.48%) as compared to R. norvegicus (41.67%), the difference however was not significant. Sarcocysts burden was higher in the diaphragm in both rat species. Generally, higher parasite load was observed in R. norvegicus. In both rat species, tissue cysts ranged from spindle-shaped/fusiform to globular and oval-shaped. The sarcocysts in the diaphragm were more varied. Consistently observed in the tongue were globular–shaped sarcocysts while either fusiform- and globular-shaped sarcocysts in the diaphragm. These differences suggest infection with more than one species of Sarcocystis. Hence, the presence of Sarcocystis spp. confirmed the infectivity of the parasite to Rattus spp. Moreover, the different morphologic characteristics observed on Sarcocystis prove the possibility of different species of the parasite harboring the Rattus spp.