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'''Family [[Togaviridae - Overview|Togaviridae]]'''
'''Family [[Togaviridae - Overview|Togaviridae]]'''
'''Genus Alphavirus'''
'''Genus ''Alphavirus'''''
Single-stranded, linear, positive-sense RNA viruses, 60-70nm in diameter.
Single-stranded, linear, positive-sense RNA viruses, 60-70nm in diameter.<ref>Bertone, J.J (2010) Viral Encephalitis in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12.</ref>
[[Image:Alphavirus.gif|300px|thumb|right|''' (Surface of an Alphavirus. This image is a computer-generated model of the surface of an alphavirus derived by cryoelectron microscopy. The spike-like structures on the virion surface are trimers composed of heterodimers of the virion surface glycoproteins E1 and E2. These spikes are used by the virus to attach to susceptible animal cells. ''Sourced from Wikimedia Commons, Copyright of the Centers for Disease Control and Prevention (CDC) Division of Vector-Borne Infectious Diseases, 2007)'' ''']]
[[Image:Alphavirus.gif|300px|thumb|right|''' (Surface of an Alphavirus. This image is a computer-generated model of the surface of an alphavirus derived by cryoelectron microscopy. The spike-like structures on the virion surface are trimers composed of heterodimers of the virion surface glycoproteins E1 and E2. These spikes are used by the virus to attach to susceptible animal cells. ''Sourced from Wikimedia Commons, Copyright of the Centers for Disease Control and Prevention (CDC) Division of Vector-Borne Infectious Diseases, 2007)'' ''']]
*Virus may be identified in brain tissue or cell culture using direct immunofluorescent staining.
*Virus may be identified in brain tissue or cell culture using direct immunofluorescent staining.
*EEE and WEE viral RNA in mosquitoes and equine tissues may be detected by reverse-transcription PCR.
*EEE and WEE viral RNA in mosquitoes and equine tissues may be detected by reverse-transcription PCR.
*ELISA can be used to detect virus in brain tissue. An antigen-capture ELISA, developed for EEE surveillance in mosquitoes, can be used where virus isolation and PCR facilities are unavailable (Brown ''et al''., 2001).
*ELISA can be used to detect virus in brain tissue. An antigen-capture ELISA, developed for EEE surveillance in mosquitoes, can be used where virus isolation and PCR facilities are unavailable. <ref>Brown, T.M, Mitchell, C.J, Nasci, R.S, Smith, G.C. and Roehrig, J.T. (2001). Detection of eastern equine encephalitis virus in infected mosquitoes using a monoclonal antibody-based antigen-capture enzyme-linked immunosorbent assay. ''Am. J. Trop. Med. Hyg.'', 65, 208-213. In: ''Manual of Diagnostic Tests and Vaccines for Terrestrial Animals'' found at http://www.oie.int/eng/normes/mmanual/A_00081.htm, accessed July 2010.</ref>
*Virus isolation is the most definitive diagnostic method for EEE or WEE. Brain is preferred, but virus has also been isolated from the liver and spleen. Samples of these tissues should be taken in duplicate, one set for virus isolation and the other placed in formalin for histopathology. Viral isolation specimens should be sent frozen unless they can be received refrigerated within 48 hours of sampling. Unless clinical signs persist for more than 5days prior to death, EEE virus is frequently isolated from equine brain tissue. WEE virus, however, is rarely isolated from tissues of infected horses. Newborn mice, chicken embryos and a number of cell culture systems can be used for virus isolation. Virus may also be isolated from cerebrospinal fluid (CSF) of acutely infected horses.
*Virus isolation is the most definitive diagnostic method for EEE or WEE. Brain is preferred, but virus has also been isolated from the liver and spleen. Samples of these tissues should be taken in duplicate, one set for virus isolation and the other placed in formalin for histopathology. Viral isolation specimens should be sent frozen unless they can be received refrigerated within 48 hours of sampling. Unless clinical signs persist for more than 5days prior to death, EEE virus is frequently isolated from equine brain tissue. WEE virus, however, is rarely isolated from tissues of infected horses. Newborn mice, chicken embryos and a number of cell culture systems can be used for virus isolation. Virus may also be isolated from cerebrospinal fluid (CSF) of acutely infected horses.
<references/>
<references/>
Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial found at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/100900.htm&word=Equine%2cencephalitis, accessed July 2010.
Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial found at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/100900.htm&word=Equine%2cencephalitis, accessed July 2010.