Sarcocystis neurona 42890 The pathogenesis of EPM is not clear because the complete life cycle is unknown. Sarcocystis neurona can parasitize all regions of the CNS, from the anterior cerebrum to the end of the spinal cord. Sarcocystis neurona schizonts and merozoites are found in neurons, mononuclear cells, glial cells, and perhaps other neural cells (USDA Agricultural Research Service: Sarcocystis neurona). Equine protozoal myeloencephalitis Cell mediated immunity is an important component of controlling this intracellular parasite (Marsh et al., 2004). Opossums (Didelphis virginiana, D. albiventris) are its definitive (reservoir) hosts and excrete oocysts and sporocysts (environmentally resistant stage)in their feces. Raccoons, armadillos, sea otters, skunks, cats and possibly other mammals are intermediate hosts (USDA Agricultural Research Service: Sarcocystis neurona). Sarcocystis neurona is the most common cause of equine protozoal myeloencephalitis (EPM) in horses in America. It is a single celled parasite belonging to the group called coccidia (Apicomplexa: Sarcocystidae) with opossums as the definitive hosts and a variety of mammals as aberrant or natural intermediate hosts . Only asexual stages have been identified in the aberrant intermediate hosts, and they are confined to the brain and spinal cord, and any part of the central nervous system (CNS) may be affected. In histologic sections of CNS, individual merozoites are about 3-5 um long and contain a single, centrally located vesicular nucleus. The sarcocysts are microscopic (~700 um long) with a 1-3 um thick sarcocyst wall. The bradyzoites are slender and tiny (~ 5 um long). Sarcocystis neurona sporocysts from opossum faeces are ~ 10 x 8 um in size (USDA Agricultural Research Service: Sarcocystis neurona). Baboon Papio cynocephalus 9556 Bank vole Clethrionomys glareolus 447135 Bear Ursus americanus 9643 Birds Passeroidea 175121 Brown Trout Salmo trutta 8032 Buffalo Bison bison 9901 Carnivores Vulpes 9625 Cat Felis catus 9685 Catfishes Siluriformes 7995 Cattle Bos taurus 9913 Chicken Gallus gallus 9031 Chimpanzee Pan troglodytes 9598 chinchillas Chinchillidae 10150 Copper Pheasant Syrmaticus soemmerringii 9067 Deer Cervus elaphus 9860 Deer mouse Peromyscus maniculatus 10042 Dog Canis familiaris 9615 Ducks Anas 8835 Ferret Mustela putorius furo 9669 Fish Hyperotreti 117565 Gerbil Gerbillina 10045 Goat Capra hircus 9925 Gray wolf Canis lupus 9612 Guinea pig Cavia porcellus 10141 Hamster Mesocricetus auratus 10036 Horse Equus caballus 9796 Human Homo sapiens 9606 Macaque Macaca fascicularis 9541 Mongolian Gerbil Meriones unguiculatus 10047 Monkey Platyrrhini 9479 Mouse Mus musculus 10090 None None Parrot Psittacidae 9224 Pig Sus scrofa 9823 Rabbit Oryctolagus cuniculus 9986 Rainbow trout Oncorhynchus mykiss 8022 Rat Rattus 10114 Raven Corvus corax 56781 sei whale Balaenoptera borealis 9768 Sheep Ovis aries 9940 Squirrel Spermophilus richardsonii 37591 Tree shrew Tupaiidae 9393 Trouts, salmons & chars Salmoninae 504568 Turkey Meleagris gallopavo 9103 Vole Microtus ochrogaster 79684 Water buffalo Bubalus bubalis 391902 Epm vaccine Epm vaccine Fort Dodge VO_0000835 Inactivated or "killed" vaccine Licensed Intramuscular injection (i.m.) In vitro-cultured merozoites, chemically inactivated(Marsh et al., 2004) Intramuscular injection (i.m.) S. neurona SAG1 Protein Vaccine VO_0004042 Subunit vaccine Research Intramuscular injection (i.m.) Polygen (MVP Laboratories, Omaha, Nebraska, USA) (Ellison and Witonsky, 2009) Intramuscular injection (i.m.) Recombinant protein preparation The horses were vaccinated on days 0 and 21 with 1 mL adjuvanted (Polygen; MVP Laboratories, Omaha, Nebraska, USA) rSnSAG1 (50 μg) or 1 mL adjuvant alone by IM injection in the left side of the neck (Ellison and Witonsky, 2009). Vaccination with rSnSAG-1 produced antibodies in horses that neutralized merozoites when tested by in vitro culture and significantly reduced clinical signs demonstrated by in vivo challenge (Ellison and Witonsky, 2009). Horses in all groups were challenged on study day 36 with S. neurona merozoites (Ellison and Witonsky, 2009). SAG1 Sarcocystis neurona 3106 VO_0011253 295682690 CDD:252367 42890 ? surface antigen 1 7.22 26504.924 333 SRS domain; pfam04092 >ADG26774.1 surface antigen 1 [Sarcocystis neurona] MTRAVLLTFLTLCSARVSLVRAGAPPQATCANGETTVTKLGSSGALRIHCPNNFRLAPRAGNDAGQMQVY ATAVAENPVNIRDVLPGASYLSVQNVPTLTVPQLPAKATSVFFHCQQQPDNQCFIQVEVAPAPRLGPNTC AALQSTIAFEVQQANETAVFSCGEGLAVFPQGSKALDEACSKEQALPSGAALAPKDGGLHLGFPQLPQQA MKICYICTNGGVQAEAAQRCEVRISVAANPDGSVPGANGAASXGAAARSAXALGLALVAGAFLHFC Protective antigen Horses were vaccinated with adjuvanted recombinant SnSAG1 (rSnSAG1)and 5 control (sham vaccinated) horses were vaccinated with adjuvant only. The effect of vaccination with rSnSAG1 on in vivo infection by S. neurona was evaluated by challenging all the horses with S. neurona merozoites. The study showed that vaccination with rSnSAG-1 produced antibodies in horses that neutralized merozoites when tested by in vitro culture and significantly reduced clinical signs demonstrated by in vivo challenge [Ref1263:Ellison and Witonsky, 2009]. Crowdus et al., 2008 journal Crowdus CA, Marsh AE, Saville WJ, Lindsay DS, Dubey JP, Granstrom DE, Howe DK 2008 158 1-2 36-43 Veterinary parasitology Ellison and Witonsky, 2009 journal Ellison S, Witonsky S 2009 73 3 176-183 Canadian journal of veterinary research = Revue canadienne de recherche veterinaire Elsheikha and Mansfield, 2004 journal Elsheikha HM, Mansfield LS 2004 94 6 452-459 Parasitology research Marsh et al., 2004 journal Marsh AE, Lakritz J, Johnson PJ, Miller MA, Chiang YW, Chu HJ 2004 5 1 34-42 Veterinary therapeutics : research in applied veterinary medicine USDA Agricultural Research Service: Sarcocystis neurona website http://www.ars.usda.gov/Main/docs.htm?docid=11028