Sarcocystis is a genus of protozoan parasites that can infect horses, among other animals. These parasites are part of the Apicomplexa phylum and have a complex life cycle involving both intermediate and definitive hosts. In horses, Sarcocystis spp. are typically transmitted through ingestion of sporocysts from contaminated feed or water. While infections in horses are often subclinical, they can occasionally lead to clinical signs such as muscle weakness, ataxia, or other neurological symptoms, depending on the species of Sarcocystis involved. This topic page aggregates peer-reviewed research studies and scholarly articles that explore the epidemiology, pathogenesis, diagnostic methods, and potential impact of Sarcocystis infections in equine populations.
Villa L, Gazzonis AL, Álvarez-García G, Diezma-Díaz C, Zanzani SA, Manfredi MT.Among Apicomplexa protozoa infecting equids, Besnoitia spp., Toxoplasma gondii and Neospora spp. represent important issues from a sanitary and zootechnical viewpoint. However, only scarce epidemiological data are available on the spread of the infections in horses and donkeys in Europe. Therefore, a serosurvey was planned to estimate the prevalence of these Sarcocystidae species in Italian equids. Serum samples from 268 horses and 18 donkeys raised in Italy were collected and serologically analyzed to detect anti-Besnoitia spp., anti-T. gondii and anti-Neospora spp. antibodies: an approach ba...
Schale S, Howe D, Yeargan M, Morrow JK, Graves A, Johnson AL.Infection by 2 or more protozoa is linked with increased severity of disease in marine mammals with protozoan encephalitis. Objective: To assess whether horses with equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona also have evidence of infection with Neospora hughesi or Toxoplasma gondii. We hypothesized that horses with EPM would be more likely than horses with cervical vertebral stenotic myelopathy (CVSM) to be positive for antibodies to multiple protozoan parasites. Methods: One hundred one horses with neurologic disease: 49 with EPM and 52 with CVSM. Methods: Case rev...
Howe DK, Yeargan M, Simpson L, Dangoudoubiyam S.Sarcocystis neurona is a member of the important phylum Apicomplexa and the primary cause of equine protozoal myeloencephalitis (EPM). Moreover, S. neurona is the best-studied species in the genus Sarcocystis, one of the most successful parasite taxa, as virtually all vertebrate animals may be infected by at least one species. Consequently, scientific investigation of S. neurona will aid in the control of EPM and neurologic disease in sea mammals, while also improving our understanding of a prominent branch on the apicomplexan phylogenetic tree. These protocols describe methods that expand the...
Sevá ADP, Pena HFJ, Nava A, Sousa AO, Holsback L, Soares RM.Morro do Diabo State Park (MDSP) is a significant remnant of the Atlantic Rain Forest in Brazil and is surrounded by rural properties. In that area, wild and domestic animals and humans are in close contact, which facilitates the two-way flow of infectious diseases among them. We assessed endoparasites in domestic livestock from all rural properties surrounding MDSP. There were sampled 197 cattle, 37 horses, 11 sheep, 25 swine, 21 dogs, one cat and 62 groups of chickens from 10 large private properties and 75 rural settlements. Eimeria spp. was present in almost all hosts, excepted in horses, ...
Bowden GD, Land KM, O'Connor RM, Fritz HM.The apicomplexan parasite Sarcocystis neurona is the primary etiologic agent of equine protozoal myeloencephalitis (EPM), a serious neurologic disease of horses. Many horses in the U.S. are at risk of developing EPM; approximately 50% of all horses in the U.S. have been exposed to S. neurona and treatments for EPM are 60-70% effective. Advancement of treatment requires new technology to identify new drugs for EPM. To address this critical need, we developed, validated, and implemented a high-throughput screen to test 725 FDA-approved compounds from the NIH clinical collections library for anti...
Zeng W, Sun L, Xiang Z, Li N, Zhang J, He Y, Li Q, Yang F, Song J, Morris J, Rosenthal BM, Sun L, Liu H, Yang Z.While Sarcocystis parasites from the muscles of donkey and horse have been characterized as different species, similarities between the parasites in these host raises questions about this assignment (Levine and Tadros, 1980; Matuschka, 1983; Odening et al., 1995b). To resolve this, we examined the tissue cysts of Sarcocystis collected from donkeys and horses were studied by morphological and molecular methods. Morphological studies performed by light microscopy (LM) revealed that each of two types of cysts were present in samples from each host type. Under LM, villar protrusions (VP) were some...
Saville WJA, Dubey JP, Marsh AE, Reed SM, Keene RO, Howe DK, Morrow J, Workman JD.Equine protozoal myeloencephalitis (EPM) is an important equine neurologic disorder, and treatments for the disease are often unrewarding. Prevention of the disease is the most important aspect for EPM, and a killed vaccine was previously developed for just that purpose. Evaluation of the vaccine had been hampered by lack of post vaccination challenge. The purpose of this study was to determine if the vaccine could prevent development of clinical signs after challenge with Sarcocystis neurona sporocysts in an equine challenge model. Seventy horses that were negative for antibodies to S. neuron...
Marsh AE, Chaney SB, Howe DK, Saville WJ, Reed SM.Several reports indicate the presence of small tissue cysts associated with Sarcocystis neurona infections. Several failed attempts to develop tissue cysts in potential intermediate host using in vitro derived parasites originally isolated from horses with equine protozoal myeloencephalitis suggest that the experimental methods to achieve bradyzoites with those isolates was not possible. Those prior studies reported the lack of detectable sarcocysts based on histology and in vivo feeding trials. A recent report of successful production and detection of small sarcocysts triggered us to review a...
There is currently no information regarding Sarcocystis neurona and Neospora hughesi infections in donkeys in Mexico. Here, we determined the presence of antibodies against S. neurona and N. hughesi in donkeys in the northern Mexican state of Durango. Serum samples of 239 domestic donkeys (Equus asinus) were assayed for S. neurona and N. hughesi antibodies using home-made enzyme-linked immunoassays; six (2.5%) of the 239 donkeys tested seropositive for S. neurona. The seroprevalence of S. neurona infection was comparable among donkeys regardless of their origin, health status, or sex. Multivar...
Gondim LSQ, Jesus RF, Ribeiro-Andrade M, Silva JCR, Siqueira DB, Marvulo MFV, Aléssio FM, Mauffrey JF, Julião FS, Savani ESMM, Soares RM, Gondim LFP.Sarcocystis neurona and Neospora spp. are protozoan parasites that induce neurological diseases in horses and other animal species. Opossums (Didelphis albiventris and Didelphis virginiana) are definitive hosts of S. neurona, which is the major cause of equine protozoal myeloencephalitis (EPM). Neospora caninum causes abortion in cattle and infects a wide range of animal species, while N. hughesi is known to induce neurologic disease in equids. The aims of this study were to investigate S. neurona and N. caninum in tissues from opossums in the northeastern Brazil, and to isolate Brazilian stra...
James KE, Smith WA, Conrad PA, Packham AE, Guerrero L, Ng M, Pusterla N.OBJECTIVE To describe the general seroprevalence of anti-Sarcocystis neurona and anti-Neospora hughesi antibodies among healthy equids by use of indirect fluorescent antibody tests and determine potential risk factors for seropositivity. DESIGN Cross-sectional study. SAMPLE Whole blood samples collected from 5,250 equids (1 sample/animal) across 18 states in the United States during October 2013. PROCEDURES Information regarding potential risk factors (geographic region, breed, primary use, sex, and age) was collected along with the blood samples. For each equid, an indirect fluorescent antibo...
Gutiérrez-Expósito D, García-Bocanegra I, Howe DK, Arenas-Montes A, Yeargan MR, Ness SL, Ortega-Mora LM, Álvarez-García G.Equine besnoitiosis, caused by Besnoitia bennetti, and equine protozoal myeloencephalitis (EPM), caused by Sarcocystis neurona and Neospora hughesi are relevant equine diseases in the Americas that have been scarcely studied in Europe. Thus, a serosurvey of these cystogenic coccidia was carried out in Southern Spain. A cross-sectional study was performed and serum samples from horses (n = 553), donkeys (n = 85) and mules (n = 83) were included. An in-house enzyme-linked immunosorbent assay (ELISA) was employed to identify a Besnoitia spp. infection and positive results were confirmed by ...
Coultous RM, Raftery AG, Shiels BR, Sutton DGM, Weir W.Sarcocystis fayeri is a canine protozoan parasite with an equine intermediate host. Historically classified as an incidental pathogen, recent literature has described the toxic effects of Sarcocystis fayeri in human food poisoning, and highlighted potential involvement in equine neuromuscular disease. Until now, horses were believed to be the exclusive intermediate host. This study reports the first molecular confirmation of S. fayeri in a donkey, and gives rise to the consideration of donkeys being a potential reservoir for the parasite. This finding is of particular importance in understandi...
Murungi EK, Kariithi HM.The apicomplexan parasite Sarcocystis neurona causes equine protozoal myeloencephalitis (EPM), a degenerative neurological disease of horses. Due to its host range expansion, S. neurona is an emerging threat that requires close monitoring. In apicomplexans, protein kinases (PKs) have been implicated in a myriad of critical functions, such as host cell invasion, cell cycle progression and host immune response evasion. Here, we used various bioinformatics methods to define the kinome of S. neurona and phylogenetic relatedness of its PKs to other apicomplexans. We identified 97 putative PKs clust...
Chaney SB, Marsh AE, Lewis S, Carman M, Howe DK, Saville WJ, Reed SM.Equine protozoal myeloencephalitis (EPM) remains a significant central nervous system disease of horses in the American continents. Sarcocystis neurona is considered the primary causative agent and its intermediate life stages are carried by a wide host-range including raccoons (Procyon lotor) in North America. S. neurona sarcocysts mature in raccoon skeletal muscle and can produce central nervous system disease in raccoons, mirroring the clinical presentation in horses. The study aimed to develop laboratory tools whereby the life cycle and various life stages of S. neurona could be better stu...
Portella LP, Cadore GC, Sangioni LA, Pellegrini LF, Fighera R, Ramos F, Vogel FS.Sarcocystis spp., Neospora spp., and Toxoplasma gondii are Apicomplexa protozoa that can infect horses. This study aimed to investigate the occurrence of antibodies against Sarcocystis spp., Neospora spp., and T. gondii in horses slaughtered in southern Brazil. The presence of histological lesions, tissue cysts, and Sarcocystis spp. DNA in the hearts of these horses was also investigated. A total of 197 paired serum and heart samples were evaluated by serology and direct microscopic examination; 50 of these samples were subjected to histopathological and PCR analyses. Antibodies against at lea...
Pusterla N, Tobin T.Equine protozoal myeloencephalitis is an infectious disease of the central nervous system caused by Sarcocystis neurona or Neospora hughesi. Affected horses routinely present with progressive and asymmetrical neurologic deficits. The diagnosis relies on the presence of neurologic signs, ruling out other neurologic disorders, and the detection of intrathecally derived antibodies to either S neurona and/or N hughesi. Recommended treatment is use of an FDA-approved anticoccidial drug formulation. Medical and supportive treatment is provided based on the severity of neurologic deficits and complic...
Ojo KK, Dangoudoubiyam S, Verma SK, Scheele S, DeRocher AE, Yeargan M, Choi R, Smith TR, Rivas KL, Hulverson MA, Barrett LK, Fan E, Maly DJ....Sarcocystis neurona is the most frequent cause of equine protozoal myeloencephalitis, a debilitating neurological disease of horses that can be difficult to treat. We identified SnCDPK1, the S. neurona homologue of calcium-dependent protein kinase 1 (CDPK1), a validated drug target in Toxoplasma gondii. SnCDPK1 shares the glycine "gatekeeper" residue of the well-characterized T. gondii enzyme, which allows the latter to be targeted by bumped kinase inhibitors. This study presents detailed molecular and phenotypic evidence that SnCDPK1 can be targeted for rational drug development. Recombinant ...
Cazarotto CJ, Balzan A, Grosskopf RK, Boito JP, Portella LP, Vogel FF, Fávero JF, de C Cucco D, Biazus AH, Machado G, Da Silva AS.Many parasitic diseases are considered asymptomatic, even though some studies have shown that they may cause pathological changes in the host. Therefore, the aim of this study was to evaluate the occurrence of antibodies against Toxoplasma gondii, Neospora spp. and Sarcocystis spp. in horses, and to identify the risk factors for disease. For this, 174 horses were studied, 90 males and 84 females aged between two and 20 years old. Blood samples were collected and stored in tubes without anticoagulant to obtain serum, which was subjected to serological tests for T. gondii, Sarcocystis spp., and...
Ribeiro MJ, Rosa MH, Bruhn FR, Garcia Ade M, Rocha CM, Guimarães AM.The present study used the indirect fluorescent antibody test (IFAT) to determine the seroprevalence of Sarcocystis neurona, Toxoplasma gondii and Neospora spp., and evaluated the variables associated with these infections among 506 apparently healthy horses, reared in the south of the state of Minas Gerais, Brazil. This study was conducted between April 2012 and October 2013. Among the horses, the true prevalence of S. neurona was 26% (95% CI: 22.0-30.4%), T. gondii 19.9% (95% CI: 15.5-24.8%) and Neospora spp. 23.9% (95% CI: 19.9-28.1%); and among the farms, 88.3% (95% CI: 74.4-91.6%), 71.6% ...
Żuraw A, Plog S, Lierz M, Gruber AD.Sarcocystis calchasi has recently been identified as the cause of pigeon protozoal encephalitis, PPE, a lethal brain disease in pigeons and parrots. While only avian species have been identified so far to be susceptible to this pathogen as definitive or intermediate hosts, we speculated whether mammals may be susceptible as well, as in Sarcocystis neurona and other related apicomplexan parasites. Specifically, we hypothesized its involvement in mammalian meningoencephalitis of unknown origin, MUO. A total of 143 archived formalin fixed, paraffin embedded brain samples with MUO from dogs, cats,...
Gennari SM, Pena HF, Lindsay DS, Lopes MG, Soares HS, Cabral AD, Vitaliano SN, Amaku M.Sarcocystis neurona and Neospora hughesi are coccidian protozoa that can cause neurological illness in horses in America. In this study we report seroprevalence of Neospora spp. andS. neurona in sera of 333 donkeys from the northeastern region of Brazil. Antibodies to Neospora spp. were detected in 2% (7 donkeys) of 333 sera tested by the indirect fluorescent antibody test (IFAT) with a cut-off dilution of 1:40. Antibodies to S. neurona were found in 3% (10 donkeys) of the samples tested by IFAT (cut-off ≥50) and 21% (69 donkeys) by the direct agglutination test (SAT ≥50). The SAT and IFAT...
Reed SM, Furr M, Howe DK, Johnson AL, MacKay RJ, Morrow JK, Pusterla N, Witonsky S.Equine protozoal myeloencephalitis (EPM) remains an important neurologic disease of horses. There are no pathognomonic clinical signs for the disease. Affected horses can have focal or multifocal central nervous system (CNS) disease. EPM can be difficult to diagnose antemortem. It is caused by either of 2 parasites, Sarcocystis neurona and Neospora hughesi, with much less known about N. hughesi. Although risk factors such as transport stress and breed and age correlations have been identified, biologic factors such as genetic predispositions of individual animals, and parasite-specific factors...
Bryan LK, Hamer SA, Shaw S, Curtis-Robles R, Auckland LD, Hodo CL, Chaffin K, Rech RR.A 10-year-old Quarter Horse gelding presented to the Texas A&M University Veterinary Teaching Hospital with a six month-history of ataxia and lameness in the hind limbs. The horse was treated presumptively for equine protozoal myeloencephalitis (EPM) based on clinical signs but was ultimately euthanized after its condition worsened. Gross lesions were limited to a small area of reddening in the gray matter of the thoracic spinal cord. Histologically, trypanosome amastigotes morphologically similar to Trypanosoma cruzi, the agent of Chagas disease in humans and dogs, were sporadically detec...
Aleman M, Shapiro K, Sisó S, Williams DC, Rejmanek D, Aguilar B, Conrad PA.Recent reports of Sarcocystis fayeri-induced toxicity in people consuming horse meat warrant investigation on the prevalence and molecular characterization of Sarcocystis spp. infection in horses. Sarcocysts in skeletal muscle of horses have been commonly regarded as an incidental finding. In this study, we investigated the prevalence of sarcocysts in skeletal muscle of horses with neuromuscular disease. Our findings indicated that S. fayeri infection was common in young mature horses with neuromuscular disease and could be associated with myopathic and neurogenic processes. The number of in...
Pusterla N, Packham A, Mackie S, Kass PH, Hunyadi L, Conrad PA.Thirty-three foals from a farm with a high exposure rate to Sarcocystis neurona were assigned to either an untreated or a diclazuril-treated group. Treated foals received daily 0.5 mg/kg of diclazuril pellets from 1 to 12 months of age. Monthly blood was tested for IgG against S. neurona using the indirect fluorescent antibody test. Following ingestion of colostral antibodies to S. neurona, there was a steady and continuous decline in seroprevalence to S. neurona until foals from both groups reached weaning age. Thereafter, the untreated foal group showed a significant increase in monthly se...
Herd HR, Sula MM, Starkey LA, Panciera RJ, Johnson EM, Snider TA, Holbrook TC.This report describes 2 genetically related paint mares, case Nos. 1 and 2, presented to the Oklahoma State University Boren Veterinary Medical Teaching Hospital for chronic weight loss and abnormal gait, respectively. Notable findings in both cases included marked persistent eosinophilia and multiple intramuscular lateral thoracic masses. Histologic examination of masses revealed eosinophilic, centrally necrotic granulomas and marked eosinophilic myositis. Granulomas in case No. 1 also contained intralesional Sarcocystis sp material, and adjacent muscle fibers contained intact protozoal cysts...
Yeargan M, de Assis Rocha I, Morrow J, Graves A, Reed SM, Howe DK.Enzyme-linked immunosorbent assays (ELISAs) based on the SnSAG surface antigens of Sarcocystis neurona provide reliable detection of infection by the parasite. Moreover, accurate serodiagnosis of equine protozoal myeloencephalitis (EPM) is achieved with the SnSAG ELISAs by measuring antibodies in serum and cerebrospinal fluid (CSF) to reveal active infection in the central nervous system. Two independent ELISAs based on recombinant (r)SnSAG2 or a chimeric fusion of SnSAG3 and SnSAG4 (rSnSAG4/3) are currently used together for EPM serodiagnosis to overcome varied antibody responses in different...
Dryburgh EL, Marsh AE, Dubey JP, Howe DK, Reed SM, Bolten KE, Pei W, Saville WJ.Sarcocystis neurona is considered the major etiologic agent of equine protozoal myeloencephalitis (EPM), a neurological disease in horses. Raccoon ( Procyon lotor ) is considered the most important intermediate host in the life cycle of S. neurona in the United States; S. neurona sarcocysts do mature in raccoon muscles, and raccoons also develop clinical signs simulating EPM. The focus of this study was to determine if sarcocysts would develop in raccoons experimentally inoculated with different host-derived strains of in vitro-cultivated S. neurona merozoites. Four raccoons were inoculated wi...
Blazejewski T, Nursimulu N, Pszenny V, Dangoudoubiyam S, Namasivayam S, Chiasson MA, Chessman K, Tonkin M, Swapna LS, Hung SS, Bridgers J....Sarcocystis neurona is a member of the coccidia, a clade of single-celled parasites of medical and veterinary importance including Eimeria, Sarcocystis, Neospora, and Toxoplasma. Unlike Eimeria, a single-host enteric pathogen, Sarcocystis, Neospora, and Toxoplasma are two-host parasites that infect and produce infectious tissue cysts in a wide range of intermediate hosts. As a genus, Sarcocystis is one of the most successful protozoan parasites; all vertebrates, including birds, reptiles, fish, and mammals are hosts to at least one Sarcocystis species. Here we sequenced Sarcocystis neurona, th...
Dangoudoubiyam S, Oliveira JB, Víquez C, Gómez-García A, González O, Romero JJ, Kwok OC, Dubey JP, Howe DK.Serum samples from 315 horses from Costa Rica, Central America, were examined for the presence of antibodies against Sarcocystis neurona, Neospora spp., and Toxoplasma gondii by using the surface antigen (SAG) SnSAG2 enzyme-linked immunosorbent assay (ELISA), the NhSAG1 ELISA, and the modified agglutination test, respectively. Anti- S. neurona antibodies were found in 42.2% of the horses by using the SnSAG2 ELISA. Anti- Neospora spp. antibodies were found in only 3.5% of the horses by using the NhSAG1 ELISA, and only 1 of these horses was confirmed seropositive by Western blot. Antibodies to T...
Ellison SP, Omara-Opyene AL, Yowell CA, Marsh AE, Dame JB.A gene encoding a major 29 kDa surface antigen from Sarcocystis neurona, the primary causative agent of equine protozoal myeloencephalitis (EPM), was cloned, sequenced, and expressed as a recombinant protein. A cDNA library was prepared in the expression vector lambda ZAP from polyA+mRNA isolated from S. neurona merozoites cultivated in vitro. Random sequencing of 96 clones identified a clone of an abundant transcript having a translated amino acid sequence with 30% identity to the 31-kDa surface antigen of Sarcocystis muris cyst merozoites. Southern blot analysis indicated that the correspond...
Furr M, Howe D, Reed S, Yeargan M.Diagnosis of equine protozoal myeloencephalitis (EPM) remains a challenge for equine practitioners. Current utilized methods have inadequate sensitivity and specificity, because of a high number of false positive results. Objective: Evaluation of antibody indices to Sarcocystis neurona should provide high sensitivity and specificity for diagnosis of EPM. Methods: Archived samples from 29 clinical patients. Methods: Archived serum and cerebrospinal fluid (CSF) samples from clinical patients with either EPM (14) or cervical vertebral compressive myelopathy (CVM) (15) were examined and tested for...
Granstrom DE, Alvarez O, Dubey JP, Comer PF, Williams NM.Schizonts of Sarcocystis neurona were identified microscopically in hematoxylin-eosin-stained spinal cord sections from 2 native Panamanian horses that exhibited clinical signs of equine protozoal myelitis (EPM). Spinal cord homogenate from a third Panamanian horse with EPM was inoculated onto monolayers of cultured bovine monocytes (M617). Intracytoplasmic schizonts containing merozoites arranged in rosette forms surrounding a central residual body first were observed 13 wk postinoculation. Parasites divided by endopolygeny and lacked rhoptries. Schizonts from each horse reacted with Sarcocys...
Lindsay DS, Dubey JP, Kennedy TJ.The present study examined the efficacy of ponazuril in inhibiting merozoite production of Sarcocystis neurona in cell cultures. Ponazuril inhibited merozoite production by more that 90% in cultures of S. neurona treated with 1.0 microg/ml ponazuril and greater than 95% inhibition of merozoite production was observed when infected cultures were treated with 5.0 microg/ml ponazuril. Ponazuril may have promise as a therapeutic agent in the treatment of S. neurona induced equine protozoal myeloencephalitis (EPM) in horses.
Granstrom DE, Dubey JP, Davis SW, Fayer R, Fox JC, Poonacha KB, Giles RC, Comer PF.Antigens of cultured Sarcocystis neurona merozoites were examined using immunoblot analysis. Blotted proteins were probed with S. cruzi, S. muris, and S. neurona antisera produced in rabbits, S. fayeri (pre- and post-infection) and S. neurona (pre- and post-inoculation) sera produced in horses, immune sera from 7 histologically confirmed cases of equine protozoal myeloencephalitis (EPM), and pre-suckle serum from a newborn foal. Eight proteins, 70, 24, 23.5, 22.5, 13, 11, 10.5, and 10 Kd, were detected only by S. neurona antiserum and/or immune serum from EPM-affected horses. Equine sera were ...
Pusterla N, Wilson WD, Conrad PA, Barr BC, Ferraro GL, Daft BM, Leutenegger CM.This study was designed to determine the relative levels of gene transcription of selected pathogens and cytokines in the brain and spinal cord of 12 horses with equine protozoal myeloencephalitis (EPM), 11 with equine herpesvirus type 1 (EHV-1) myeloencephalopathy, and 12 healthy control horses by applying a real time pcr to the formalin-fixed and paraffin-embedded tissues. Total rna was extracted from each tissue, transcribed to complementary dna (cDNA) and assayed for Sarcocystis neurona, Neospora hughesi, EHV-1, equine GAPDH (housekeeping gene), tumour necrosis factor (TNF)-alpha, interfer...
Marsh AE, Barr BC, Madigan J, Lakritz J, Nordhausen R, Conrad PA.Neosporosis was diagnosed in an 11-year-old Quarter Horse gelding with clinical signs and diagnostic test results compatible with equine protozoal myeloencephalitis (EPM). Presumptive postmortem diagnosis of EPM attributable to Sarcocystis neurona infection is generally made on the basis of detecting an antibody titer to S neurona in the CSF or characteristic histologic lesions, even when parasites have not been specifically identified. Neosporosis was confirmed in the horse described here by use of immunohistochemical examination, in vitro culturing, and ultrastructural and molecular characte...
Mansfield LS, Mehler S, Nelson K, Elsheikha HM, Murphy AJ, Knust B, Tanhauser SM, Gearhart PM, Rossano MG, Bowman DD, Schott HC, Patterson JS.We tested the hypothesis that brown-headed cowbirds (Molothrus ater) harbor Sarcocystis neurona, the agent of equine protozoal myeloencephalitis (EPM), and act as intermediate hosts for this parasite. In summer 1999, wild caught brown-headed cowbirds were collected and necropsied to determine infection rate with Sarcocystis spp. by macroscopic inspection. Seven of 381 (1.8%) birds had grossly visible sarcocysts in leg muscles with none in breast muscles. Histopathology revealed two classes of sarcocysts in leg muscles, thin-walled and thick-walled suggesting two species. Electron microscopy sh...
Lindsay DS, Mitchell SM, Vianna MC, Dubey JP.Equine protozoal myeloencephalitis is a major cause of neurological disease in horses from the Americas. Horses are considered accidental intermediate hosts. The structure of sporocysts of the causative agent, Sarcocystis neurona, has never been described. Sporocysts of S. neurona were obtained from the intestines of a laboratory-raised opossum fed skeletal muscles from a raccoon that had been fed sporocysts. Sporocysts were 11.3 by 8.2 microm and contained 4 sporozoites. The appearance of the sporocyst residuum was variable. The residuum of some sporocysts was composed of many dispersed granu...
Marsh AE, Johnson PJ, Ramos-Vara J, Johnson GC.Little information is available about antigenic variation of Sarcocystis neurona isolated from horses with equine protozoal myeloencephalitis, nor is there much information available on the specific antibody pattern to S. neurona antigens of horses from different geographic regions where S. neurona isolates have been obtained. This communication reports on the characterization of a new S. neurona isolate, SN-MU1. The isolate was obtained from a 3-year old Thoroughbred that had asymmetrical neurological signs and localized skeletal muscle atrophy. This S. neurona isolate is similar to other S. ...
Mullaney T, Murphy AJ, Kiupel M, Bell JA, Rossano MG, Mansfield LS.Opossums (Didelphis spp.) are the definitive host for the protozoan parasite Sarcocystis neurona, the causative agent of equine protozoal myeloencephalitis (EPM). Opossums shed sporocysts in feces that can be ingested by true intermediate hosts (cats, raccoons, skunks, armadillos and sea otters). Horses acquire the parasite by ingestion of feed or water contaminated by opossum feces. However, horses have been classified as aberrant intermediate hosts because the terminal asexual sarcocyst stage that is required for transmission to the definitive host has not been found in their tissues despite...
Johnson AL, Morrow JK, Sweeney RW.Recent research suggests that serum : CSF titer ratios could provide the most accurate antemortem diagnosis of equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona. Objective: The purpose of this study was to assess the utility of two commercially available tests, the indirect fluorescent antibody test (IFAT) and the surface antigen 2, 4/3 ELISA (SAG2, 4/3 ELISA), using archived paired serum and CSF samples. Methods: Samples were obtained from 4 types of clinical patients. Confirmed positive cases (n = 9 horses; 11 sample sets) had neurologic deficits and postmortem lesions c...
Zeng W, Sun L, Xiang Z, Li N, Zhang J, He Y, Li Q, Yang F, Song J, Morris J, Rosenthal BM, Sun L, Liu H, Yang Z.While Sarcocystis parasites from the muscles of donkey and horse have been characterized as different species, similarities between the parasites in these host raises questions about this assignment (Levine and Tadros, 1980; Matuschka, 1983; Odening et al., 1995b). To resolve this, we examined the tissue cysts of Sarcocystis collected from donkeys and horses were studied by morphological and molecular methods. Morphological studies performed by light microscopy (LM) revealed that each of two types of cysts were present in samples from each host type. Under LM, villar protrusions (VP) were some...
Blythe LL, Granstrom DE, Hansen DE, Walker LL, Bartlett J, Stamper S.To determine seroprevalence of antibodies to Sarcocystis neurona in neurologically normal horses residing in 4 regions of Oregon and to describe the effects of age, gender, breed, and housing on seroprevalence within each region. Methods: Prevalence survey. Methods: Serum samples from 334 horses systematically selected by practicing veterinarians. Methods: Antibodies to S neurona were measured in sera, using a western blot. Information including age, gender, breed, housing, geographic location, and duration of residence was obtained for each horse. Data were analyzed, using descriptive statist...
Aleman M, Shapiro K, Sisó S, Williams DC, Rejmanek D, Aguilar B, Conrad PA.Recent reports of Sarcocystis fayeri-induced toxicity in people consuming horse meat warrant investigation on the prevalence and molecular characterization of Sarcocystis spp. infection in horses. Sarcocysts in skeletal muscle of horses have been commonly regarded as an incidental finding. In this study, we investigated the prevalence of sarcocysts in skeletal muscle of horses with neuromuscular disease. Our findings indicated that S. fayeri infection was common in young mature horses with neuromuscular disease and could be associated with myopathic and neurogenic processes. The number of in...
Gennari SM, Pena HF, Lindsay DS, Lopes MG, Soares HS, Cabral AD, Vitaliano SN, Amaku M.Sarcocystis neurona and Neospora hughesi are coccidian protozoa that can cause neurological illness in horses in America. In this study we report seroprevalence of Neospora spp. andS. neurona in sera of 333 donkeys from the northeastern region of Brazil. Antibodies to Neospora spp. were detected in 2% (7 donkeys) of 333 sera tested by the indirect fluorescent antibody test (IFAT) with a cut-off dilution of 1:40. Antibodies to S. neurona were found in 3% (10 donkeys) of the samples tested by IFAT (cut-off ≥50) and 21% (69 donkeys) by the direct agglutination test (SAT ≥50). The SAT and IFAT...
Bryan LK, Hamer SA, Shaw S, Curtis-Robles R, Auckland LD, Hodo CL, Chaffin K, Rech RR.A 10-year-old Quarter Horse gelding presented to the Texas A&M University Veterinary Teaching Hospital with a six month-history of ataxia and lameness in the hind limbs. The horse was treated presumptively for equine protozoal myeloencephalitis (EPM) based on clinical signs but was ultimately euthanized after its condition worsened. Gross lesions were limited to a small area of reddening in the gray matter of the thoracic spinal cord. Histologically, trypanosome amastigotes morphologically similar to Trypanosoma cruzi, the agent of Chagas disease in humans and dogs, were sporadically detec...
Marsh AE, Barr BC, Madigan J, Lakritz J, Conrad PA.To identify Sarcocystis neurona-specific DNA sequences in the nuclear small subunit ribosomal RNA (nss-rRNA) gene that could be used to distinguish S neurona from other closely related protozoal parasites, and to evaluate a polymerase chain reaction (PCR) test, using broad based primers and a unique species-specific probe on CSF for detection of S neurona in equids. Methods: Sequencing of the nuclear small subunit ribosomal RNA gene from a new S neurona isolate (UCD 1) was performed. The sequence was compared with that of other closely related Sarcocystidae parasites. From this sequence, conse...
Mansfield LS, Schott HC, Murphy AJ, Rossano MG, Tanhauser SM, Patterson JS, Nelson K, Ewart SL, Marteniuk JV, Bowman DD, Kaneene JB.Sarcocystis neurona is a protozoan parasite that can cause neurological deficits in infected horses. The route of transmission is by fecal-oral transfer of sporocysts from opossums. However, the species identity and the lifecycle are not completely known. In this study, Sarcocystis merozoites from eight isolates obtained from Michigan horses were compared to S. neurona from a California horse (UCD1), Sarcocystis from a grackle (Cornell), and five Sarcocystis isolates from feral opossums from Michigan. Comparisons were made using several techniques. SDS-PAGE analysis with silver staining showed...
Bentz BG, Granstrom DE, Stamper S.To determine seroprevalence of Sarcocystis neurona-specific antibodies in a population of horses residing in Chester County, Pa. Methods: Prevalence survey. Methods: 117 serum samples from selected members of a population of 580 Thoroughbred horses. Methods: Serum was analyzed for antibodies to Sarcocystic neurona, using a western blot. Information regarding age, sex, and housing of horse was obtained by questionnaire. Data were analyzed, using multivariable logistic regression. Results: Seroprevalence was 45.3% (95% CI, 36.3 to 54.3%). A relationship was not found between seroprevalence and s...
Duarte PC, Daft BM, Conrad PA, Packham AE, Gardner IA.A serum indirect fluorescent antibody test (IFAT) was compared with a Western blot (WB) and a modified Western blot (mWB) for diagnosis of equine protozoal myeloencephalitis (EPM). Using receiver-operating characteristic (ROC) analysis, the area under the curve of the IFAT was greater than the areaunder the curves of the WB and the mWB (P = 0.025 and P = 0.044, respectively). There was no statistically significant difference between the areas under the curves of the WBs (P > 0.05). On the basis of an arbitrarily chosen cut-off titer for a positive test result of 1:80 for the IFAT and interpret...
Erber M, Geisel O.The prevalence of Sarcocystis spp. in horses was investigated in a survey at the Munich abattoir during 1978/79. Muscle specimens (oesophagus, diaphragm, sublingual muscle, myocardium) were examined using tryptic digestion. Out of 200 horses 31 (15.5%) were found to be carriers of sarcocysts. No parasites were found in the myocardium. In three animals sarcocysts could be isolated and differentiated in fresh preparations. Cysts with 5 to 11 microns by less than 0.5 microns hairlike, unstable protrusions were classified as Sarcocystis equicanis, whereas those with 2.5 to 4.5 microns by 0.8 to 1....
Sellon DC, Knowles DP, Greiner EC, Long MT, Hines MT, Hochstatter T, Hasel KM, Ueti M, Gillis K, Dame JB.Sarcocystis neurona is an apicomplexan parasite that is the primary etiologic agent of equine protozoal myeloencephalitis in horses. Protective immune responses in horses have not been determined, but interferon-gamma (IFN-gamma) is considered critical for protection from neurologic disease in mice. The role of adaptive and innate immune responses in control of parasites was explored by infecting BALB/c, IFN-gamma knockout (GKO), and severe combined immune deficient (SCID) mice with S. neurona (10(4) sporocysts/mouse). Immune competent BALB/c mice eliminated parasites within 30 days, with no s...
Pusterla N, Tamez-Trevino E, White A, Vangeem J, Packham A, Conrad PA, Kass P.Equine protozoal myeloencephalitis is a commonly diagnosed neurological disease of horses in North America and is caused by infection with Sarcocystis neurona or Neospora hughesi. The aim of this study was to compare prevalence factors among horses seropositive or seronegative to N. hughesi and/or S. neurona. A total of 3123 submissions were included in the study, with horses originating from 49 States. Thirty-eight animals from 21 States tested seropositive for N. hughesi only, 840 horses from 40 States were seropositive for S. neurona only, 25 horses from 14 States were seropositive for both...
Murphy AJ, Mansfield LS.Sarcocystis neurona is a protozoan parasite that causes a neurological disease in horses called equine protozoal myeloencephalitis. The route of transmission is speculated to be by fecal-oral transfer of sporocysts shed from opossums. Controversy exists regarding both the natural life cycle for this parasite as well as the species identity of opossum Sarcocystis. To provide stage-specific material for species comparison, 27 opossums from southern Michigan were screened for Sarcocystis spp. sporocysts. Seven opossums were positive for Sarcocystis sporocysts by fecal flotation. A simplified, eff...
Hammerschmitt ME, Henker LC, Lichtler J, da Costa FVA, Soares RM, Llano HAB, Pavarini SP.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 fou...
Rossano MG, Mansfield LS, Kaneene JB, Murphy AJ, Brown CM, Schott HC, Fox JC.Equine protozoal myeloencephalitis (EPM) is a neurological disease of horses and ponies caused by the apicomplexan protozoan parasite Sarcocystis neurona. The purposes of this study were to develop the most stringent criteria possible for a positive test result, to estimate the sensitivity and specificity of the EPM Western blot antibody test, and to assess the ability of bovine antibodies to Sarcocystis cruzi to act as a blocking agent to minimize false-positive results in the western blot test for S. neurona. Sarcocystis neurona merozoites harvested from equine dermal cell culture were heat ...
Gargala G, Le Goff L, Ballet JJ, Favennec L, Stachulski AV, Rossignol JF.Sarcocystis neurona is an obligate intracellular parasite that causes equine protozoal myeloencephalitis (EPM). The aim of this work was to document inhibitory activities of nitazoxanide (NTZ, [2-acetolyloxy-N-(5-nitro 2-thiazolyl) benzamide]) and new thiazolides/thiadiazolides on S. neurona in vitro development, and investigate their structure-activity relationships. S. neurona was grown in bovine turbinate cell cultures. At concentrations varying from 1.0 to 5.0mg/L, nitazoxanide and 21 of 32 second generation thiazolide/thiadiazolide agents exerted a > or =95% maximum inhibition on S. neuro...
