First Identification of Pathogenic and Zoonotic-Relevant Sarcocystis hominis and Other Sarcocystis Species in Slaughtered Cattle in Chile

Sarcocystis species are apicomplexan protozoa infecting a wide range of domestic and wild animals, including cattle, in which several species are of zoonotic relevance. This study reports, for the first time, the detection and molecular identification of pathogenic and zoonotic Sarcocystis hominis in slaughtered cattle from Central Chile. A total of 200 muscle samples (100 = myocardium, 100 = diaphragm) were examined by macroscopic inspection and tissue homogenization. Selected samples were additionally analyzed by histology, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and multiplex real-time PCR targeting the 18S rDNA. No macroscopic sarcocysts were observed, nonetheless microscopic sarcocysts were detected in 56% of assessed samples, with higher infection rates in the heart (91%) than in the diaphragm (21%). SEM and TEM analyses revealed thin-walled sarcocysts with finger-like protrusions in the diaphragm, as well as flattened hair-like projections in the myocardium. Molecular analysis identified Sarcocystis cruzi in all positive samples and detected additional DNA of Sarcocystis bovifelis/Sarcocystis rommeli and for the first time the zoonotic species S. hominis. These findings confirm the coexistence of canine-, feline-, and human-transmitted Sarcocystis species in Chilean cattle and highlight potential public health implications associated with consumption of raw or undercooked S. hominis-carrying beef meat. This constitutes the first molecular evidence of S. hominis in Chile, emphasizing the need for further surveillance and control measures in the meat production chain. These novel data on human S. hominis infections in Chile confirm the importance of initiating investigations on human sarcocystosis as this enteric parasitic disease is still sparsely considered by local public health authorities.