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Dubey JP, Howe DK, Furr M, Saville WJ, Marsh AE, Reed SM, Grigg ME. An update on Sarcocystis neurona infections in animals and equine protozoal myeloencephalitis (EPM). Vet Parasitol 2015; 209:1-42. [PMID: 25737052 DOI: 10.1016/j.vetpar.2015.01.026] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 01/27/2015] [Accepted: 01/29/2015] [Indexed: 01/27/2023]
Abstract
Equine protozoal myeloencephalitis (EPM) is a serious disease of horses, and its management continues to be a challenge for veterinarians. The protozoan Sarcocystis neurona is most commonly associated with EPM. S. neurona has emerged as a common cause of mortality in marine mammals, especially sea otters (Enhydra lutris). EPM-like illness has also been recorded in several other mammals, including domestic dogs and cats. This paper updates S. neurona and EPM information from the last 15 years on the advances regarding life cycle, molecular biology, epidemiology, clinical signs, diagnosis, treatment and control.
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Affiliation(s)
- J P Dubey
- United States Department of Agriculture, Agricultural Research Service, Animal Parasitic Diseases Laboratory, Beltsville Agricultural Research Center, Building 1001, Beltsville, MD 20705-2350, USA.
| | - D K Howe
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546-0099, USA
| | - M Furr
- Marion du Pont Scott Equine Medical Center, Virginia Maryland Regional College of Veterinary Medicine, 17690 Old Waterford Road, Leesburg, VA 20176, USA
| | - W J Saville
- Department of Veterinary Preventive Medicine, The Ohio State University, 1920 Coffey Road, Columbus, OH 43210, USA
| | - A E Marsh
- Department of Veterinary Preventive Medicine, The Ohio State University, 1920 Coffey Road, Columbus, OH 43210, USA
| | - S M Reed
- Rood and Riddle Equine Hospital, Lexington, KY 40511, USA
| | - M E Grigg
- Molecular Parasitology Section, Laboratory of Parasitic Diseases, National Institutes of Health, National Institutes of Allergy, and Infectious Diseases, 4 Center Drive, Room B1-06, Bethesda, MD 20892, USA
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Howe DK, Gaji RY, Marsh AE, Patil BA, Saville WJ, Lindsay DS, Dubey JP, Granstrom DE. Strains of Sarcocystis neurona exhibit differences in their surface antigens, including the absence of the major surface antigen SnSAG1. Int J Parasitol 2007; 38:623-31. [PMID: 17980881 DOI: 10.1016/j.ijpara.2007.09.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Revised: 09/17/2007] [Accepted: 09/24/2007] [Indexed: 12/01/2022]
Abstract
A gene family of surface antigens is expressed by merozoites of Sarcocystis neurona, the primary cause of equine protozoal myeloencephalitis (EPM). These surface proteins, designated SnSAGs, are immunodominant and therefore excellent candidates for development of EPM diagnostics or vaccines. Prior work had identified an EPM isolate lacking the major surface antigen SnSAG1, thus suggesting there may be some diversity in the SnSAGs expressed by different S. neurona isolates. Therefore, a bioinformatic, molecular and immunological study was conducted to assess conservation of the SnSAGs. Examination of an expressed sequence tag (EST) database revealed several notable SnSAG polymorphisms. In particular, the EST information implied that the EPM strain SN4 lacked the major surface antigen SnSAG1. The absence of this surface antigen from the SN4 strain was confirmed by both Western blot and Southern blot. To evaluate SnSAG polymorphisms in the S. neurona population, 14 strains were examined by Western blots using monospecific polyclonal antibodies against the four described SnSAGs. The results of these analyses demonstrated that SnSAG2, SnSAG3, and SnSAG4 are present in all 14 S. neurona strains tested, although some variance in SnSAG4 was observed. Importantly, SnSAG1 was not detected in seven of the strains, which included isolates from four cases of EPM and a case of fatal meningoencephalitis in a sea otter. Genetic analyses by PCR using gene-specific primers confirmed the absence of the SnSAG1 locus in six of these seven strains. Collectively, the data indicated that there is heterogeneity in the surface antigen composition of different S. neurona isolates, which is an important consideration for development of serological tests and prospective vaccines for EPM. Furthermore, the diversity reported herein likely extends to other phenotypes, such as strain virulence, and may have implications for the phylogeny of the various Sarcocystis spp. that undergo sexual stages of their life cycle in opossums.
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Affiliation(s)
- Daniel K Howe
- Department of Veterinary Science, University of Kentucky, Lexington, KY 40546-0099, USA.
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Asmundsson IM, Dubey JP, Rosenthal BM. A genetically diverse but distinct North American population of Sarcocystis neurona includes an overrepresented clone described by 12 microsatellite alleles. INFECTION GENETICS AND EVOLUTION 2006; 6:352-60. [PMID: 16488197 DOI: 10.1016/j.meegid.2006.01.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Revised: 12/30/2005] [Accepted: 01/02/2006] [Indexed: 11/20/2022]
Abstract
The population genetics and systematics of most coccidians remain poorly defined despite their impact on human and veterinary health. Non-recombinant parasite clones characterized by distinct transmission and pathogenesis traits persist in the coccidian Toxoplasma gondii despite opportunities for sexual recombination. In order to determine whether this may be generally true for tissue-cyst forming coccidia, and to address evolutionary and taxonomic problems within the genus Sarcocystis, we characterized polymorphic microsatellite markers in Sarcocystis neurona, the major causative agent of equine protozoal myeloencephalitis (EPM). Bayesian statistical modeling, phylogenetic reconstruction based on genotypic chord distances, and analyses of linkage disequilibrium were employed to examine the population structure within S. neurona and closely related Sarcocystis falcatula isolates from North and South America. North American S. neurona were clearly differentiated from those of South America and also from isolates of S. falcatula. Although S. neurona is characterized by substantial allelic and genotypic diversity typical of interbreeding populations, one genotype occurs with significantly excessive frequency; thus, some degree of asexual propagation of S. neurona clones may naturally occur. Finally, S. neurona isolated from disparate North American localities and diverse hosts (opossums, a Southern sea otter, and horses) comprise a single genetic population. Isolates associated with clinical neurological disease bear no obvious distinction as measured by these presumably neutral genetic markers.
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Affiliation(s)
- Ingrid M Asmundsson
- Animal Parasitic Disease Laboratory, Animal and Natural Resources Institute, Agricultural Research Service, United States Department of Agriculture, Beltsville, MD 20705, USA
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Katayama Y, Wada R, Kanemaru T, Sasagawa T, Uchiyama T, Matsumura T, Anzai T. First case report of Sarcocystis neurona-induced equine protozoal myeloencephalitis in Japan. J Vet Med Sci 2003; 65:757-9. [PMID: 12867742 DOI: 10.1292/jvms.65.757] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Equine protozoal myeloencephalitis developed in a three-year-old male Thoroughbred racehorse imported from the United States. The animal showed astasia five days after the onset of ataxia. Histopathologically, focal nonpurulent myelitis accompanied by hemorrhage and perivascular infiltration was observed in the fourth and fifth cervical spinal cord. Immunohistochemically, shizonts were occasionally observed and were positive for anti-Sarcocystis neurona (S. neurona) antiserum. S. neurona-specific antibodies were detected in the serum and cerebrospinal fluid by Western blot. This is the first equine protozoal myeloencephalitis case in Japan.
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Affiliation(s)
- Yoshinari Katayama
- Epizootic Research Station, Equine Research Institute, Japan Racing Association, Tochigi, Japan
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Dubey JP, Saville WJ, Stanek JF, Lindsay DS, Rosenthal BM, Oglesbee MJ, Rosypal AC, Njoku CJ, Stich RW, Kwok OC, Shen SK, Hamir AN, Reed SM. Sarcocystis neurona infections in raccoons (Procyon lotor): evidence for natural infection with sarcocysts, transmission of infection to opossums (Didelphis virginiana), and experimental induction of neurologic disease in raccoons. Vet Parasitol 2001; 100:117-29. [PMID: 11698157 DOI: 10.1016/s0304-4017(01)00500-3] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Equine protozoal myeloencephalitis (EPM) is a serious neurologic disease of horses in the Americas and Sarcocystis neurona is the most common etiologic agent. The distribution of S. neurona infections follows the geographical distributions of its definitive hosts, opossums (Didelphis virginiana, Didelphis albiventris). Recently, cats and skunks were reported as experimental and armadillos as natural intermediate hosts of S. neurona. In the present report, raccoons (Procyon lotor) were identified as a natural intermediate host of S. neurona. Two laboratory-raised opossums were found to shed S. neurona-like sporocysts after ingesting tongues of naturally-infected raccoons. Interferon-gamma gene knockout (KO) mice fed raccoon-opossum-derived sporocysts developed neurologic signs. S. neurona was identified immunohistochemically in tissues of KO mice fed sporocysts and the parasite was isolated in cell cultures inoculated with infected KO mouse tissues. The DNA obtained from the tongue of a naturally-infected raccoon, brains of KO mice that had neurological signs, and from the organisms recovered in cell cultures inoculated with brains of neurologic KO mice, corresponded to that of S. neurona. Two raccoons fed mature S. neurona sarcocysts did not shed sporocysts in their feces, indicating raccoons are not likely to be its definitive host. Two raccoons fed sporocysts from opossum feces developed clinical illness and S. neurona-associated encephalomyelitis was found in raccoons killed 14 and 22 days after feeding sporocysts; schizonts and merozoites were seen in encephalitic lesions.
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Affiliation(s)
- J P Dubey
- United States Department of Agriculture, Agricultural Research Service, Animal and Natural Resources Institute, Parasite Biology, Epidemiology and Systematics Laboratory, Building 1001, Beltsville, MD 20705-2350, USA.
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Dubey JP, Lindsay DS, Saville WJ, Reed SM, Granstrom DE, Speer CA. A review of Sarcocystis neurona and equine protozoal myeloencephalitis (EPM). Vet Parasitol 2001; 95:89-131. [PMID: 11223193 DOI: 10.1016/s0304-4017(00)00384-8] [Citation(s) in RCA: 225] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Equine protozoal myeloencephalitis (EPM) is a serious neurological disease of horses in the Americas. The protozoan most commonly associated with EPM is Sarcocystis neurona. The complete life cycle of S. neurona is unknown, including its natural intermediate host that harbors its sarcocyst. Opossums (Didelphis virginiana, Didelphis albiventris) are its definitive hosts. Horses are considered its aberrant hosts because only schizonts and merozoites (no sarcocysts) are found in horses. EPM-like disease occurs in a variety of mammals including cats, mink, raccoons, skunks, Pacific harbor seals, ponies, and Southern sea otters. Cats can act as an experimental intermediate host harboring the sarcocyst stage after ingesting sporocysts. This paper reviews information on the history, structure, life cycle, biology, pathogenesis, induction of disease in animals, clinical signs, diagnosis, pathology, epidemiology, and treatment of EPM caused by S. neurona.
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Affiliation(s)
- J P Dubey
- United States Department of Agriculture, Agricultural Research Service, Animal and Natural Resources Institute, Beltsville Agricultural Research Center, MD 20705-2350, USA.
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Abstract
The ultrastructure of Sarcocystis neurona schizonts and merozoites was studied in specimens derived from cell culture and from the brains of infected mice. Schizonts and merozoites were located in the host cell cytoplasm without a parasitophorous vacuole at any stage of development. Merozoites divided by endopolygeny. Fully formed merozoites had a pellicle, numerous polysomes and ribosomes, smooth and rough endoplasmic reticulum, 22 subpellicular microtubules, 9-16 dense granules, 25-75 micronemes, a plastid, a Golgi complex, 1-3 mitochondria, a conoid, 2 apical rings, 2 polar rings, 0-6 lipid bodies, a nucleus and nucleolus, but no rhoptries. Most micronemes were located anterior to the nucleus including 1-6 micronemes in the conoid. Merozoites were either slender (7.3 microm x 1.7 microm) or stumpy (7.7 microm x 3.1 microm). Dense granules appeared to arise from the maturation face of the Golgi complex. The ultrastructure of in vitro derived schizonts and merozoites were similar to in vivo derived organisms.
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Affiliation(s)
- C A Speer
- Department of Veterinary Molecular Biology, Montana State University, Bozeman 59717-3610, USA
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Lindsay DS, Dykstra CC, Williams A, Spencer JA, Lenz SD, Palma K, Dubey JP, Blagburn BL. Inoculation of Sarcocystis neurona merozoites into the central nervous system of horses. Vet Parasitol 2000; 92:157-63. [PMID: 10946139 DOI: 10.1016/s0304-4017(00)00281-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Equine protozoal myeloencephalitis (EPM) is a neurologic syndrome in horses from the Americas and is usually caused by infection with the apicomplexan parasite, Sarcocystis neurona. A horse model of EPM is needed to test the efficacy of chemotherapeutic agents and potential vaccines. Five horses that were negative for antibodies to S. neurona in their serum and cerebrospinal fluid (CSF) were injected in the subarachnoid space with living merozoites of the SN2 isolate of S. neurona. None of the horses developed clinical disease or died over a 132-day observation period. All five horses developed antibodies to S. neurona in their CSF and serum 3-4 weeks after injection. Two of the horses were examined at necropsy and no parasite induced lesions were observed in their tissues and no parasites were recovered from portions of their spinal cords inoculated on to cell cultures. Results of this study demonstrate that merozoites of the SN2 isolate of S. neurona will induce seroconversion but not clinical disease when inoculated directly into the CSF of nonimmune horses.
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Affiliation(s)
- D S Lindsay
- Department of Biomedical Sciences and Pathobiology, Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, 24061-0342, USA.
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Kent Scarratt W, Buechner-Maxwell VA, Karzenski S, Wallace MA, Robertson JL. Urinary incontinence and incoordination in three horses associated with equine protozoal myeloencephalitis. J Equine Vet Sci 1999. [DOI: 10.1016/s0737-0806(06)82198-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Dubey JP, Mattson DE, Speer CA, Baker RJ, Mulrooney DM, Tornquist SJ, Hamir AN, Gerros TC. Characterization of a Sarcocystis neurona isolate (SN6) from a naturally infected horse from Oregon. J Eukaryot Microbiol 1999; 46:500-6. [PMID: 10519218 DOI: 10.1111/j.1550-7408.1999.tb06067.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An isolate of Sarcocystis neurona (SN6) was obtained from the spinal cord of a horse from Oregon with neurologic signs. The parasite was isolated in cultures of bovine monocytes and equine spleen cells. The parasite divided by endopolygeny and completed at least one asexual cycle in cell cultures in three days. Two gamma interferon knockout mice inoculated with cell culture-derived merozoites became ill 35 d later and S. neurona schizonts and merozoites were found in encephalitic lesions. The parasite in tissue sections of mice reacted with S. neurona-specific antibodies and S. neurona was reisolated from the brain of knockout mice.
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Affiliation(s)
- J P Dubey
- United States Department of Agriculture, Agricultural Research Service, Beltsville Agricultural Research Center, Maryland 20705-2350, USA.
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Tillotson K, McCue PM, Granstrom DE, Dargatz DA, Smith MO, Traub-Dargatz JL. Seroprevalence of antibodies to Sarcocystis neurona in horses residing in northern Colorado. J Equine Vet Sci 1999. [DOI: 10.1016/s0737-0806(99)80102-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Dubey JP, Lindsay DS. Isolation in immunodeficient mice of Sarcocystis neurona from opossum (Didelphis virginiana) faeces, and its differentiation from Sarcocystis falcatula. Int J Parasitol 1998; 28:1823-8. [PMID: 9925260 DOI: 10.1016/s0020-7519(98)00166-0] [Citation(s) in RCA: 146] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Sarcocystis neurona was isolated in nude mice and gamma-interferon knockout mice fed sporocysts from faeces of naturally infected opossums (Didelphis virginiana). Mice fed sporocysts became lethargic and developed encephalitis. Protozoa were first found in the brain starting 21 days post-inoculation. Sarcocystis neurona was recovered in cell culture from the homogenate of liver, spleen and brain of a nude mouse 11 days after feeding sporocysts. The protozoa in mouse brain and in cell culture multiplied by schizogony and mature schizonts often had a residual body. Sarcocystis falcatula, which has an avian-opossum cycle, was not infective to nude or knockout mice. Protozoa were not found in tissues of nude mice or knockout mice after subcutaneous injection with culture-derived S. falcatula merozoites and sporocysts from the faeces of opossums presumed to contain only S. falcatula. Results demonstrate that S. neurona is distinct from S. falcatula, and that opossums are hosts for both species.
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Affiliation(s)
- J P Dubey
- US Department of Agriculture, Agricultural Research Service, Livestock and Poultry Sciences Institute, BARC, Beltsville, MD 20705-2350, USA.
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Liang FT, Granstrom DE, Zhao XM, Timoney JF. Evidence that surface proteins Sn14 and Sn16 of Sarcocystis neurona merozoites are involved in infection and immunity. Infect Immun 1998; 66:1834-8. [PMID: 9573058 PMCID: PMC108132 DOI: 10.1128/iai.66.5.1834-1838.1998] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/1997] [Accepted: 01/29/1998] [Indexed: 02/07/2023] Open
Abstract
Sarcocystis neurona is the etiologic agent of equine protozoal myeloencephalitis (EPM). Based on an analysis of 25,000 equine serum and cerebrospinal fluid (CSF) samples, including samples from horses with neurologic signs typical of EPM or with histologically or parasitologically confirmed EPM, four major immunoblot band patterns have been identified. Twenty-three serum and CSF samples representing each of the four immunoblot patterns were selected from 220 samples from horses with neurologic signs resembling EPM and examined for inhibitory effects on the infectivity of S. neurona by an in vitro neutralization assay. A high correlation between immunoblot band pattern and neutralizing activity was detected. Two proteins, Sn14 and Sn16 (14 and 16 kDa, respectively), appeared to be important for in vitro infection. A combination of the results of surface protein labeling, immunoprecipitation, Western blotting, and trypsin digestion suggests that these molecules are surface proteins and may be useful components of a vaccine against S. neurona infection. Although S. neurona is an obligate intracellular parasite, it is potentially a target for specific antibodies which may lyse merozoites via complement or inhibit their attachment and penetration to host cells.
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Affiliation(s)
- F T Liang
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington 40546-0099, USA
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Moore D, White N. Differentiation between musculoskeletal and neurologic causes of lameness in horses: 22 cases (1993–1995). J Equine Vet Sci 1998. [DOI: 10.1016/s0737-0806(98)80188-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Moore LA, Johnson PJ, Messer NT, Kline KL, Crump LM, Knibb JR. Management of headshaking in three horses by treatment for protozoal myeloencephalitis. Vet Rec 1997; 141:264-7. [PMID: 9316239 DOI: 10.1136/vr.141.11.264] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Unlike the incidence of equine protozoal myeloencephalitis (EPM), which appears to be increasing, headshaking is an uncommon problem for horses in Missouri and the adjacent states. Equine protozoal myeloencephalitis was incriminated in three horses examined for the treatment of headshaking on the basis of a neurological examination, an analysis of cerebrospinal fluid and their response to treatment. The headshaking and stereotypical behaviour associated with EPM was successfully treated with potentiated sulphonamides and pyrimethamine.
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Affiliation(s)
- L A Moore
- Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia 65211, USA
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Granstrom DE, Dubey JP, Davis SW, Fayer R, Fox JC, Poonacha KB, Giles RC, Comer PF. Equine protozoal myeloencephalitis: antigen analysis of cultured Sarcocystis neurona merozoites. J Vet Diagn Invest 1993; 5:88-90. [PMID: 8466988 DOI: 10.1177/104063879300500118] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
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 titered by the indirect immunofluorescent antibody (IFA) method using air-dried, cultured S. neurona merozoites. Anti-Sarcocystis IFA titers were found in horses with or without EPM. Serum titers did not correspond to the number of specific bands recognized on immunoblots.
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Affiliation(s)
- D E Granstrom
- Department of Veterinary Science, University of Kentucky, Lexington 40546-0099
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