Background: Over the years the mammalian fauna, including artiodactyls, has been decreasing and changing due to the entry of bioinvaders into Conservation Units, highlighting, the free-living pig, Sus scrofa, also called feral pig or wild boar. As it is an exotic animal, it is relevant to analyze the gastrointestinal parasites, highlighting those with zoonotic potential that may be infecting these animals and native artiodactyls. To expand this information, this study aims to evaluate the gastrointestinal parasites of artiodactyls in fecal samples collected in the Pedra Selada State Park and in its buffer zones in Rio de Janeiro.

Methodology/Main Findings: Between 2020 and 2021, 101 fecal samples were collected with morphology compatible with artiodactyls in different areas of the Park. All collection points were georeferenced and plotted on maps. Part of the fecal material was submitted to identification of the host species by means of macroscopic and molecular analysis from PCR with primers that amplify the DNA fragment of the COI gene. The other part was submitted to parasite research by qualitative and quantitative coproparasitological techniques. The fecal samples that presented cysts of the Phylum Ciliophora were analyzed with primers that amplify a DNA fragment from the ITS1.5.8S.ITS2 region. Of the 101 samples collected, 72 (71.3%) were found in the covered areas of Pavão Valley, 24 (23.8%) in Grama Valley and 5 (4.9%) in Redondo Mountain. In general, it can be seen that the average length of stool varied very little. Regarding the average values of the weights, it can be seen that they varied a lot, highlighting a diversity of artiodactyls possibly associated with different age groups and sizes of the animals. Morphologically, the feces presented brownish coloration, were in the form of pellets, were rounded and slightly pointed, characteristics that are typically associated with the Order Artiodactyla. Regarding host identification through molecular analysis with the COI gene, 79 samples were identified as belonging to Sus scrofa and 2 as belonging to Mazama gouazoubira. In general, forms of protozoa are more evident than helminths. Protozoan cysts of the Phylum Ciliophora were the most detected forms of parasites, being present in 40 (39.6%) fecal samples. These structures were found only in the feces of Sus scrofa. In addition to these, other parasites were also identified in the feces of these animals, such as non-sporulated coccidian oocyst (2.9%), Ascaris spp. (1.8%), Metrastrongylus spp. (5.9%), strongylid eggs (3.9%), Trichuris spp. (3.9%), nematode larvae (7.9%) and taxonomically unidentified nematode egg (1%). Of the 40 samples in which cysts were detected, nucleotide sequences of protozoa of the Phylum Ciliophora originated from 26 can be interpreted, all of which are compatible with Balantioides coli. Of these, 13 were classified as genetic variant of type B0, one of type B1, 11 of type A0 and were only characterized as type A, not being fully framed in any of the pre-established subtypes.

Conclusions/Significance: It should be noted that parasites with zoonotic potential such as B. coli, highlighting the genetic variant of A0, were identified in the samples collected from Park and their buffer zones, this being the first study in Brazil that phylogenetically characterized this protozoan in free-living S. scrofa feces, placing this bioinvader as one of the reservoirs of this parasite.