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Equine Protozoal Myeloencephalitis (view source)
Revision as of 13:12, 19 July 2010
, 13:12, 19 July 2010→Pathology
====Pathology====
====Pathology====
[[Image:Equine_Protozoal_Myeloencephalitis.jpg|600px|thumb|left|''' Sarcocystis neurona stages and lesions.
[[Image:Equine_Protozoal_Myeloencephalitis.jpg|600px|thumb|left|''' Sarcocystis neurona stages and lesions.
(H). An oocyst with two sporocysts each with banana-shaped sporozoites. Unstained.
(H). An oocyst with two sporocysts each with banana-shaped sporozoites. Unstained.
Created by the ''Agricultural Research Service, the research agency of the United States Department of Agriculture'', July 2005. ''Sourced from the USDA Agricultural Research Service page on EPM/Sarcocystis neurona, located via WikiMedia Commons.'' ''']]
Created by the ''Agricultural Research Service, the research agency of the United States Department of Agriculture'', July 2005. ''Sourced from the USDA Agricultural Research Service page on EPM/Sarcocystis neurona, located via WikiMedia Commons.'' ''']]
Widespread lesions of the CNS are typically observed in horses.<ref name="Furr">Furr, M (2010) ''Equine protozoal myeloencephalitis'' in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12.</ref>
=====Gross exam=====
Lesions may be up to several centimetres across.<ref name="Furr">Furr, M (2010) ''Equine protozoal myeloencephalitis'' in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12.</ref> They range from mild discolouration to multifocal areas of haemorrhage and/or malacia<ref name="Merck">Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial</ref> of the brain, spinal cord and less commonly, peripheral nerves.<ref name="Furr">Furr, M (2010) ''Equine protozoal myeloencephalitis'' in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12.</ref>
=====Histopathology=====
Microscopically, both grey and white matter may be affected with focal to diffuse areas of nonsuppurative inflammation, necrosis and neuronal destruction. Perivascular infiltrates comprise lymphocytes, macrophages, plasma cells, giant cells, eosinophils and gitter cells.<ref name="Furr">Furr, M (2010) ''Equine protozoal myeloencephalitis'' in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12.</ref> In around 25% of cases, schizonts or merozoites may be found in the neuronal cytoplasm.<ref name="Merck">Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial</ref> Less frequently, protozoa parasitize intravascular and tissue neutrophils and eosinophils, capillary endothelial cells and myelinated axons<ref name="Furr">Furr, M (2010) ''Equine protozoal myeloencephalitis'' in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12.</ref><ref name="Merck">Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial</ref>. Free merozoites may be seen in necrotic regions. If organisms are absent, the diagnosis relies on recognition of the inflammatory changes described above.<ref name="Merck">Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial</ref>
====Treatment====
====Treatment====