Molecular detection of Sarcocystis sp. in a kept under human care black capuchin monkey (Sapajus nigritus., Goldfuss 1809) with necrotizing encephalitis.

A senile male black capuchin monkey (Sapajus nigritus) kept under human care in a Zoo was found dead after 2 weeks presenting signals of weight loss and hyporexia. Histopathological revealed a necrotizing encephalitis. Although it was not observed microscopically, Sarcocystis sp infection was detected in brain tissue from molecular assays. These infections have been rarely described in neotropical primates, particularly associated with tissue lesions.

Diversity of Sarcocystis parasites in southeastern Baltic Sea catchment ecosystems.

Currently, research on apicomplexan Sarcocystis parasites is mainly carried out by analyzing animal carcasses. However, environmental studies would not only allow faster detection of possible sources of infection but also avoid the use of animals for investigations. Therefore, in the current study, we aimed to identify tested Sarcocystis species in sediment collected from water bodies located in the southeastern Baltic countries. A total of 99 sediment samples were collected during the summer from different types of water bodies in Estonia, Latvia, Lithuania, and Poland. Species-specific nested PCR targeting cox1 gene was used for the detection of selected Sarcocystis species (S. cruzi, S. bovifelis, S. hirsuta, S. arieticanis, S. tenella, S. capracanis, S. miescheriana, and S. bertrami) infecting livestock. The results showed a statistically lower (p < 0.05) occurrence of Sarcocystis parasites in Estonia (50%) compared to three countries, where the detection rate of Sarcocystis spp. DNA was remarkably higher, ranging from 88 to 100%. Among Sarcocystis species tested, S. cruzi (83.8%) and S. arieticanis (55.6%) using cattle and sheep as their intermediate hosts were most commonly identified. The detection rates of some of the analyzed Sarcocystis species were significantly different in southeastern Baltic countries. It is discussed that the detection rates of certain Sarcocystis species depend not only on the number of animals per 1 km2 but also on various ecological factors and farming practices that differ in the amount of contact domestic animals have with predators and the potential for animals to become infected through natural water or food sources.

Microscopic detection and molecular characterization of Sarcocystis miescheriana in wild boars (Sus scrofa): first report from Greece.

The genus Sarcocystis includes protozoan parasites with an indirect life cycle. Sarcocystis spp. can infect various animal species and humans, causing sarcocystosis, a parasitosis of economic importance and zoonotic concern. Wild boars can act as intermediate hosts for Sarcocystis miescheriana and the zoonotic Sarcocystis suihominis that infects humans by consumption of raw or undercooked infected swine meat. In the present study, the diaphragmatic muscle tissue of 123 wild boars hunted in Greece was examined to determine the frequency of Sarcocystis spp. The samples were examined by tissue compression and molecular techniques. Under light microscopy, 34 out of 123 (27.6%) wild boars tested positive for Sarcocystis spp., while a higher infection prevalence (75%) was revealed by multiplex PCR performed in 100 of the samples. The partial mtDNA cox1 gene (~ 1100 bp) of 20 samples tested positive for S. miescheriana by multiplex PCR was amplified and sequenced. Sarcocystis miescheriana was identified as the only species involved in these infections. This is the first study on the prevalence of Sarcocystis spp. in wild animals in Greece. Further, large-scale surveys are needed to assess the prevalence and species of this parasite in Greece and to design efficient control and preventive measures in a One Health perspective.

First report of Sarcocystis falcatula in naturally infected Razorbill auks (Alca torda) collected in Tunisian Mediterranean Sea shores.

Sarcocystis spp. are apicomplexan cyst-forming parasites that can infect numerous vertebrates, including birds. Sarcosporidiosis infection was investigated in three muscles (breast, right and left thigh muscle) and one organ (heart) of four Razorbill auks (Alca torda) stranded between November and December 2022 on the shores of the Mediterranean Sea in Nabeul and Bizerte governorates, Northern Tunisia. Two of the four tested A. torda were PCR positive for 18S rRNA Sarcocystis spp. gene. Among the examined 16 muscles/organs, only one breast and one right thigh were Sarcocystis spp. PCR-positive (12.5% ± 8.3, 2/16). Our results showed a relatively high molecular prevalence of Sarcocystis spp. in Razorbill auks (A. torda). Sarcocystis spp. sequence described in the present study (GenBank number: OR516818) showed 99.56-100% identity to Sarcocystis falcatula. In conclusion, our results confirmed the infection of Razorbill auks (A. torda) by S. falcatula. Further research is needed on different migratory seabirds' species in order to identify other Sarcocystis species.

Parasites in a hotspot: diversity and specificity patterns of apicomplexans infecting reptiles from the Socotra Archipelago.

Although parasites represent a major component of biodiversity, they remain poorly assessed, especially in remote regions. In this study, we screened 461 reptiles from Socotra, the largest and most biologically diverse archipelago in Arabia. Using 18S rRNA primers, we detected various apicomplexan parasites, namely haemogregarines, sarcocystids and eimeriids. Haemogregarines were the most common and genetically diverse, followed by sarcocystids (genus Sarcocystis) and eimeriids (genera Isospora and Lankesterella). All were related to parasites of other reptiles, including species from Arabia, Northern Africa and Asia. Like their 29 endemic reptile hosts, almost all Socotran parasites presented high genetic divergence and ecological differences from those found elsewhere, and probably represent undescribed endemic species. Among hosts, skinks were the most parasitized, which contrasted with similar studies from other areas, probably due to their more generalist diet and habitat use. As expected due to its high species richness, geckos harboured the highest parasite diversity in the archipelago. Parasite diversity also seemed to be correlated to island size, as the largest island harboured most haplotypes. This study emphasizes the importance of screening parasites in wild hosts from remote regions and of considering host ecology to understand disease transmission across taxa.

Molecular identification of Sarcocystis species in diaphragm muscle tissue of European mouflon (Ovis gmelini musimon) from Austria.

Previous morphological studies suggested that mouflon may have sarcocysts similar to those of sheep. However, to date, no molecular-based studies of the species of Sarcocystis infecting mouflon have been done. The present study identified Sarcocystis species in diaphragm muscle samples from 20 European mouflon (Ovis gmelini musimon). Molecular identification using the cox1 sequence analysis was performed on sarcocysts excised from muscle tissue and on DNA from digested muscle samples. Both frequency and intensity of infection in mouflon were high with 19 of 20 animals testing Sarcocystis positive and > 50 cysts per gram of tissue recovered from 10 of the 19 Sarcocystis positive animals. Molecular analysis revealed dominant Sarcocystis tenella (18/19 animals) and Sarcocystis arieticanis (1/19 animals), whose known intermediate hosts are sheep. In addition, Sarcocystis capracanis, which is known to form sarcocysts in goats, was detected in two animals. The results of this study demonstrated the digestion method to be superior over the direct isolation of sarcocysts for the molecular identification of Sarcocystis species in a certain host. Future research of Sarcocystis diversity in wild ovine and caprine species is needed.

First description of Sarcocystis species infecting Barbary sheep (Ammotragus lervia).

Barbary sheep (Ammotragus lervia) is a North African native wild Caprinae, introduced in the 1970s in new territories such as Spain, the USA, and Mexico. Here, we describe Sarcocystis species in Barbary sheep. Sarcocysts were found in 19 out of 56 adult A. lervia in Southern Spain and characterized morphologically and molecularly. By light microscopy, sarcocysts had thin (< 1 µm) or thick (> 2 µm) walls. By transmission electron microscopy, sarcocysts with thick walls had Type 14 villar protrusions corresponding to S. tenella/S. capracanis of domestic sheep (Ovis aries) or goats (Capra hircus). Sarcocysts with thin walls had Type 7b villar protrusions that corresponded to S. arieticanis/S. hircicanis of domestic sheep or goats. Molecular analyses allowed the identification of only thick-walled Sarcocystis species. Six sarcocysts were assigned to S. tenella (99.2-100% and 95.6-100% sequence similarity within 18S rRNA and COI, respectively) and 19 sarcocysts were assigned to S. capracanis (98.5-99.8% and 97.9-99.0% sequence similarity within 18S rRNA and COI, respectively). Further studies are needed for taxonomic identification of sarcocysts in Barbary sheep because Sarcocystis species in sheep and goats are not cross transmissible despite morphological similarities.

Invasive American mink (Neovison vison) as potential definitive host of Sarcocystis elongata, S. entzerothi, S. japonica, S. truncata and S. silva using different cervid species as intermediate hosts.

Canids and scavenger birds were shown to act as definitive hosts of numerous Sarcocystis species using members of the Cervidae family as an intermediate host, whereas definitive hosts spreading closely related S. elongata, S. entzerothi, S. japonica, S. matsuoae, S. rangiferi, S. truncata, S. silva and S. tarandi remain unknown. In the current study, the intestine samples of 40 American minks (Neovison vison) were molecularly tested for the presence of the above-mentioned Sarcocystis spp. Species-specific PCR of cytochrome c oxidase subunit I (cox1) fragments and subsequent sequencing revealed the presence of sporocysts/oocysts of five species, S. elongata (n=2), S. entzerothi (n=10), S. japonica (n=4), S. silva (n=13) and S. truncata (n=21) in the analysed samples. Sarcocystis infection was confirmed in 32/40 (80%) examined samples. In addition, half of the infected animals (50%) were infected with multiple Sarcocystis species suggesting that American minks had access to meat of different deer species, such as roe deer, red deer and sika deer. This causes concern about compliance of hunters and game processing companies with game waste management rules. Further research on the involvement of mustelids in the transmission of various Sarcocystis spp. from different geographical locations is needed.

Molecular identification of Sarcocystis wobeseri-like parasites in a new intermediate host species, the white-tailed sea eagle (Haliaeetus albicilla).

A reintroduced white-tailed sea eagle (Haliaeetus albicilla) in moderate body condition was found dead and submitted for post-mortem examination. There were no signs of disease on gross pathological examination. Histopathological examination however revealed the presence of encysted protozoan parasites in pectoral and cardiac muscle sections. Polymerase chain reaction amplification of extracted genomic DNA and sequencing of four regions: the 18S rDNA, 28S rDNA, internal transcribed spacer (ITS) 1, and RNA polymerase B (rpoB) loci, confirmed the presence of a Sarcocystis species in pectoral and cardiac muscle which appeared phylogenetically similar to Sarcocystis wobeseri. This is the first report of S. wobeseri-like infection in a white-tailed sea eagle revealing a new intermediate host species for this parasite.

Morphologic and molecular identification of three macroscopic Sarcocystis species infecting domestic sheep (Ovis aries) and cattle (Bos taurus) in Egypt.

In a survey study on the macroscopic species of Sarcocystis infecting domestic sheep (Ovis aries) and cattle (Bos taurus) in Egypt, the macrosarcocysts of Sarcocystis gigantea and Sarcocystis medusiformis were detected in the carcasses of 33 domestic sheep out of a total of 250 (13.20%), whereas Sarcocystis hirsuta macrosarcocysts were found in 17 out of 150 cattle (11.33%) slaughtered at the municipal abattoirs of two different provinces in Egypt. The sarcocysts of each species were thoroughly described morphologically through gross inspection, histopathologic and transmission electron microscopic (TEM) examination. By TEM, S. gigantea primary cyst wall was 6-7.5 µm thick and had irregular highly branched cauliflower-like villar protrusions (VP).The VP contained microtubules (mt) and multiple electron dense granules (edg) that were dispersed inside the cores of the branched VP. Besides, the parasitophorous vacuolar membrane (PVM) had minute blister-like invaginations all over the entire surface of the sarcocyst. S. medusiformis cyst had a thin sarcocyst wall (~2 µm thick) as compared to that of S. gigantea. The cyst wall had trapezoidal or nearly pyramidal VP that were surrounded by thick PVM in addition to a ground substance GS that contained electron-dense fine particles. S. hirsuta sarcocyst wall was 7-9 µm thick and possessed rhomboid-shaped VP that contained microtubules (mt) and electron-dense granules (edg) of variable sizes. The edg were arranged in rows and running parallel to the longitudinal axis of the protrusions. The VP had characteristic narrow neck-like constrictions at their bases, dilated middle portions, and tapered distal ends. The detected macrosarcocysts were eventually confirmed by molecular characterization on the levels of 18S rRNA, 28S rRNA, and Cox1 sequences. Phylogenetic analyses based on the sequences of the 18S rRNA and Cox1 genetic markers gave rise to robust associations of the currently identified isolates of S. gigantea, S. medusiformis, and S. hirsuta within a major clade of Sarcocystis species with felines as presumed or known definitive hosts.

Lesions caused by Sarcocystis spp., parasites of opossums (Didelphis aurita), in acute and chronic infections in birds (Melopsittacus undulatus).

Protozoa of the genus Sarcocystis are obligatory heterogenous parasites with both definitive and intermediate hosts. Opossums (Didelphis aurita) can shed multiple species of Sarcocystis with birds as the intermediate host. The pathologies of Sarcocystis species in birds have not been thoroughly elucidated. Therefore, the aim of the present study to determine the main lesions that can occur in acute and chronic infections in intermediate hosts, when they ingest infective sporocysts that are shed in the opossum's feces, using budgerigars as a model. To this end, 12 budgerigars, Melopsittacus undulatus, were divided into two groups that received an inoculum with 60 and 120 sporocysts. Birds that died or were euthanized were necropsied, and the lung, tongue, liver, brain, heart, and skeletal striated muscles were collected and fixed in 10% formalin for histopathological analysis. The infectivity varied according to the sample and infective dose. Acute histopathological lesions were characterized by evidence of slightly degenerated hepatocyte cords that permeated the region of the blood vessel and hepatic sinusoids. Pulmonary tissue lesions were also observed in the parabronchial region with the presence of inflammatory infiltrates associated with areas of edema and atelectasis. In chronic infections, few mature cysts were observed in the chest, and many mature cysts in the thigh and tongue muscles. Thus, it was possible to conclude that lesions are highly characteristic in acute infection and, in chronic infections, cysts were present but without major lesions. In this case, the preferred organs of parasitism were the thigh and the tongue.

Preliminary findings and molecular characterization of thin-walled Sarcocystis species in hearts of cattle and buffaloes in Thailand, Lao PDR, and Cambodia.

Cattle and buffaloes, popular protein sources worldwide, are intermediate hosts for several Sarcocystis species. These coccidian protozoans cause sarcocystosis resulting in subclinical and chronic infections in striated muscles by forming macrocysts or microcysts. In Thailand, Lao People's Democratic Republic, and Cambodia, Sarcocystis species have been reported, but molecular identification has been lacking. This study investigates the prevalence of infection, histo-morphology, and molecular identification of Sarcocystis species in hearts of cattle and buffalo sold in local markets. A phylogenetic tree inferred from a portion of the 18S ribosomal (r) RNA gene was used to identify the genus and species of Sarcocystis. The mitochondrial cytochrome c oxidase subunit 1 (cox-1 gene) was sequenced to confirm the species of host tissue. In Thailand, Sarcocystis was detected in 66.7% (14/21) of samples. In Lao People's Democratic Republic, 90% (9/10) of samples were infected and in Cambodia 100% (8/8). For the first time from these countries, we report Sarcocystis cruzi, Sarcocystis heydorni, and Sarcocystis levinei found in taurine cattle (Bos taurus) and water buffalo (Bubalus bubalis). Zoonotic protozoan transmission needs to be controlled by inspection activities by local health inspectors, and appropriate action is required at all points in the food chain by competent authorities to protect consumer health and prevent sarcocystosis in cattle and water buffaloes.

Muscular Sarcocystosis in Sheep Associated With Lymphoplasmacytic Myositis and Expression of Major Histocompatibility Complex Class I and II.

Sarcocystosis is a protozoal disease affecting a wide range of animals. The aims of this study were to characterize the following in sheep: (1) the muscle pathology in Sarcocystis infection, (2) the inflammatory infiltrate and its relationship to severity of infection, and (3) immune markers expressed by parasitized muscle fibers and parasitic cysts. Skeletal muscle samples from 78 sheep slaughtered in southern Italy were snap frozen and analyzed by histopathology, immunohistochemistry, and immunofluorescence. Polymerase chain reaction (PCR) and sequencing were used for Sarcocystis species identification. All 40 muscle samples tested were PCR-positive for Sarcocystis tenella. Histologically, cysts were identified in 76/78 cases (97%), associated with an endomysial infiltrate of lymphocytes and plasma cells. The T cells were predominantly CD8+, with fewer CD4+ or CD79α+ cells. Eosinophils were absent. Notably, sarcolemmal immunopositivity for major histocompatibility complex (MHC) I and II was found in 76/78 cases (97%) and 75/78 cases (96%), respectively, both in samples with and in those without evident inflammatory infiltrate. The number of cysts was positively correlated with inflammation. In addition, MHC I was detected in 55/78 cyst walls (72%), and occasionally co-localized with the membrane-associated protein dystrophin. The findings suggest that muscle fibers respond to the presence of cysts by expression of MHC I and II. The possible role of MHC I and II in the inflammatory response and on the cyst wall is also discussed.

Molecular phylogeny of Sarcocystis fayeri (Apicomplexa: Sarcocystidae) from the domestic horse Equus caballus based on 18S rRNA gene sequences and its prevalence.

Sarcocystosis is a parasitic disease caused by an intracellular protozoan parasite Sarcocystis belonging to the phylum Apicomplexa. These parasites have a requisite two-host life cycle. Recently, there are many Sarcocystis species that identified morphologically. In the present study, diaphragmatic muscle samples from the domestic horse (Equus caballus) were examined for Sarcocystis infection. The natural infection with sarcocysts was recorded to be 62·5% for only microcysts in the infected muscles. Molecular analysis using the 18S rRNA gene was conducted to swiftly and accurately identify the recovered species. Studies on the expression of the 18S rRNA gene have confirmed that the present parasite isolates belong to the Sarcocystis genus. The sequence data showed significant identities (>80%) with archived gene sequences from species within the Sarcocystidae family, and a dendrogram showing the phylogenetic relationship was constructed. The most closely related species were the previously described Sarcocystis fayeri and Sarcocystis bertrami. The current data showed that the present species was identified as S. fayeri and deposited in GenBank (accession number MF614956.1). This study highlights the importance of the genetic data in the exact taxonomy within sarcocystid species.

Presence of Sarcocystis sybillensis in Japanese sika deer (Cervus nippon) captured in its native territory and its phylogenetic relationship with Sarcocystis nipponi.

The first study reporting the morphological characterization of Sarcocystis sybillensis was performed in 1983; however, without any molecular analysis. Sarcocystis nipponi has been recently described as a species synonymic to S. sybillensis. We reconfirmed the presence of S. sybillensis in Japanese sika deer (Cervus nippon) captured in its native territory; and performed its molecular and phylogenetic characterization. The morphological characteristics of the sarcocysts were consistent with those of S. nipponi and S. sybillensis described in the first report. However, the nucleotide sequence of 18S rRNA gene of S. sybillensis showed only 91.9% identity to that of S. nipponi, suggesting low homology among the concerned Sarcocystis spp. Accordingly, S. sybillensis was found to occupy a clade distinct from that of S. nipponi in a phylogenetic tree of Sarcocystis. Therefore, the present study provides essential information on 18S rRNA-based molecular characterization of S. sybillensis and disproves the existing notion of morphology-based species synonymity of S. sibillensis and S. nipponi. These results also suggest that S. sybillensis belongs to type 2 Sarcocystis.

First molecular characterization of Sarcocystis neurona causing meningoencephalitis in a domestic cat in Brazil.

Sarcocystis neurona is the main agent associated with equine protozoal myeloencephalitis (EPM). Apart from horses, S. neurona has been occasionally described causing neurologic disease in several other terrestrial animals as well as mortality in marine mammals. Herein, we describe the clinical, pathological, and molecular findings of a fatal case of S. neurona-associated meningoencephalitis in a domestic cat. The causing agent was analyzed by multilocus genotyping, confirming the presence of S. neurona DNA in the tissue samples of the affected animal. Significant molecular differences were found in relation to S. neurona isolates detected in other regions of the Americas. In addition, the parasite was identical to Sarcocystis sp. identified in opossum sporocysts in Brazil at molecular level, which suggests that transmission of. S. neurona in Brazil might involve variants of the parasite different from those found elsewhere in the Americas. Studies including more samples of S. neurona would be required to test this hypothesis, as well as to assess the impact of this diversity.

Genetic characterization and phylogenetic analysis of Sarcocystis suihominis infecting domestic pigs (Sus scrofa) in India.

A total of 57 tissue samples of domestic pigs (Sus scrofa) were collected from the meat outlets of five north Indian states and examined for sarcocystosis by histological and molecular methods. The genomic DNA extracted from five representative positive isolates was subjected to PCR amplification of the partial 18S rRNA gene followed by cloning and sequencing. Sequence analysis of the newly generated Indian isolates recorded 96.9-100.0% identity with published sequences of Sarcocystis suihominis. Two new haplotypes that have not been previously described manifested 99.5-100.0% nucleotide homology within themselves. In the phylogenetic analysis, Indian isolates of S. suihominis grouped together with S. suihominis originating from Italy, and they collectively formed a sister clade with Sarcocystis miescheriana within a clade containing various Sarcocystis spp. of ruminants having felids as final hosts. At the same time, this clade separated from a sister clade containing Sarcocystis spp. of bovid or cervid ruminants using canids as known or surmised definitive host. The current study established the phylogenetic relationship of Indian isolates of S. suihominis with various Sarcocystis spp. as well as with other taxa of Sarcocystidae family based on 18S rRNA gene for the first time.

Molecular characterisation of five Sarcocystis species in domestic sheep (Ovis aries) from Spain.

The major aim of the present study was to determine by molecular methods whether the wide and narrow types of macroscopic sarcocysts in Spanish sheep belonged to different species, that is, Sarcocystis gigantea and Sarcocystis medusiformis, respectively. Additionally, we wanted to identify and characterize molecularly the species forming microscopic sarcocysts and determine the phylogenetic placement of all species found. Portions of the oesophagus, diaphragm and hind legs containing macroscopic sarcocysts were collected from slaughtered culled ewes at an abattoir in the Province of Madrid, Central Spain, but both macroscopic and microscopic sarcocysts were isolated for molecular examination. Genomic DNA from 63 sarcocysts (21 macroscopic, 42 microscopic) were examined at the cytochrome c oxidase subunit I gene (cox1), while selected isolates of each species found were further examined at the 18S and 28S ribosomal RNA (rRNA) genes. The 63 sarcocysts comprised five cox1 sequence types, each corresponding to a particular sarcocyst type, and thus represented five Sarcocystis spp. The slender fusiform and thick macrocysts belonged to S. medusiformis and S. gigantea, respectively. The microscopic sarcocysts belonged to Sarcocystis arieticanis, Sarcocystis tenella and a Sarcocystis mihoensis-like species with slanting thorn-like cyst wall protrusions, which was characterised molecularly for the first time. Based on its phylogenetic position, the S. mihoensis-like species probably uses corvids as definitive hosts.

Sarcocystis spp. diversity in the roe deer (Capreolus capreolus) from Lithuania and Spain.

The roe deer (Capreolus capreolus) has been identified as an intermediate host for six known Sarcocystis species, S. capreolicanis, S. entzerothi, S. gracilis, S. linearis, S. oviformis, and S. silva. In this study, we identified Sarcocystis species in the diaphragm and tongue muscles from the Lithuanian and Spanish roe deer, respectively, on the basis of a microscopic examination and DNA analysis. A total of 43 and 27 sarcocysts were isolated and characterized from the Lithuanian and Spanish roe deer, respectively. Overall six Sarcocystis species were identified in roe deer from Lithuania, and only three of them, S. gracilis, S. linearis, and S. silva were found to have infecting animals from Spain. The current paper represents first molecular results of Sarcocystis species in the Spanish roe deer. Furthermore, transmission electron microscopy examination revealed specific wall structure of sarcocysts studied, S. linearis was characterized by ribbon-like villar protrusions (vp) (type 8a), and S. oviformis was distinguished by elongated vp resembling spades or mushroom-like structures (type 39). Based on 18S rDNA and cox1 sequences, Sarcocystis species from the roe deer showed considerable intraspecific genetic variability. However, similar values of intraspecific genetic variation were estimated at both genes analysed. The highest variability was observed for S. capreolicanis and S. linearis in both genes and for S. silva at cox1. Consequently, the level of genetic variability of Sarcocystis from the roe deer varied depending on species rather than on gene analysed or geographical area.

Pathological, immunohistochemical, and molecular findings of equine protozoal myeloencephalitis due to Sarcocystis neurona infection in Brazilian horses.

Equine protozoal myeloencephalitis (EPM) is an important neurologic disease of horses in the American continent caused by Sarcocystis neurona and Neospora hughesi infection. This study describes the pathological, immunohistochemical, and molecular findings of fatal cases of EPM in southern Brazil. A review was performed on a total of 13 cases compatible with EPM, which were diagnosed by postmortem examination in the period of 2010-2017. Epidemiological information was obtained from necropsy reports. Gross and histological lesions were characterized, and cases were subjected to immunohistochemistry anti-Sarcocystis neurona, Toxoplasma gondii, and Neospora spp. Molecular search was performed using ITS-1 gene PCRs. Microscopic lesions were multifocal in all cases, and more frequently observed in the spinal cord segments and in the rhombencephalon. Intralesional protozoans were histologically detected in five horses, while a positive immunostaining for S. neurona was observed in eleven cases (11/13). Through molecular techniques, six positive cases for the ITS-1 gene were detected, and obtained sequences presented highest similarity with S. neurona. EPM due to S. neurona infection represents an important neurologic disease of horses in Brazil and this disease should be considered as a main differential diagnosis in horses presenting neurologic signs.