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

## TL;DR

This study is the first to identify zoonotic Sarcocystis hominis in cattle in Chile, highlighting a potential food safety risk from consuming raw or undercooked beef.

## Contribution

The first molecular detection of zoonotic Sarcocystis hominis in Chilean cattle, revealing new public health implications.

## Key findings

- Sarcocystis hominis, a zoonotic parasite, was detected for the first time in Chilean cattle.
- Microscopic sarcocysts were found in 56% of samples, with higher prevalence in heart muscle.
- Multiple Sarcocystis species, including those transmissible to humans, coexist in Chilean cattle.

## Abstract

Cattle can harbor muscle parasites of the genus Sarcocystis that are not detectable during routine slaughterhouse inspection but may have important implications for animal production and public health. Some of these parasites are zoonotic, meaning they can be transmitted from animals to humans through the consumption of raw or undercooked beef, causing intestinal disease. In Chile, information on the presence of these parasites in cattle destined for human consumption has been lacking. The aim of this study was to determine the occurrence and species composition of these parasites in slaughtered cattle from central Chile. Muscle samples from the heart and diaphragm of cattle were examined using microscopic and genetic methods. Although no parasites were visible to the naked eye, microscopic infection was common, particularly in the heart muscle. Importantly, this study provides the first evidence in Chile of a zoonotic parasite species in cattle, together with other species of veterinary importance. These results demonstrate that cattle in Chile participate in parasite transmission cycles involving animals and humans and highlight a potential food safety risk. These findings contribute to a better understanding of the occurrence of Sarcocystis spp. in cattle and underscore the value of ongoing monitoring to support food safety and animal health.

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.