Changes

==Epidemiology==

==Epidemiology==

===Distribution===

===Distribution===

Togaviral encephalitis in equids is largely confined to the Western Hemisphere.<ref name="multiple">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>  Venezuelan EEV can cause large outbreaks of disease over extensive geographical areas in both humans and horses.  Spread of this virus into Central America has had disasterous consequences with epidemics as far north as Texas. Climatic conditions and interventions that support vector populations, such as irrigation, greatly influence the geographical spread of the disease.  EEE has been recorded across the United States, but mostly in the Southeastern States. As its names suggests, WEE has a predilection for the Western states which have been subject to significant outbreaks in the past.  A regional alteration in virulence has been proposed for the steep decline in clinical case numbers observed in this area.  A lag phase of 2-5weeks is commonly observed between horse and human cases of WEE in a given locus.  Both are dead-end hosts for the virus.    A subtype of Western EEV, Highlands J virus, was isolated from the brain of a horse with encephalitis in Florida (Karabatsos ''et al''., 1988).

Togaviral encephalitis in equids is largely confined to the Western Hemisphere.<ref name="multiple">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>  Venezuelan EEV can cause large outbreaks of disease over extensive geographical areas in both humans and horses.  Spread of this virus into Central America has had disasterous consequences with epidemics as far north as Texas.<ref name="duplicate">http://www.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/viralenceph/index.htm, accessed July 2010</ref> Climatic conditions and interventions that support vector populations, such as irrigation, greatly influence the geographical spread of the disease.<ref name="duplicate">http://www.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/viralenceph/index.htm, accessed July 2010</ref> EEE has been recorded across the United States, but mostly in the Southeastern States.<ref name="multiple">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>  As its names suggests, WEE has a predilection for the Western states which have been subject to significant outbreaks in the past.  A regional alteration in virulence has been proposed for the steep decline in clinical case numbers observed in this area.<ref name="multiple">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> A lag phase of 2-5weeks is commonly observed between horse and human cases of WEE in a given locus.<ref>McLintock, J (1980) The arbovirus problem in Canada, ''Can J Public Health'', 67(Suppl 1):8-12. In: 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> Both are dead-end hosts for the virus.    A subtype of Western EEV, Highlands J virus, was isolated from the brain of a horse with encephalitis in Florida.<ref>Karabatsos, N, Lewis, A.L, Calisher, C.H, Hunt, A.R, and Roehrig, J.T (1988). Identification of Highland J virus from a Florida horse. ''Am J Trop Med Hyg'', 39, 603-606. 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>

===Transmission===

===Transmission===

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.

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.

Walton T.E. (1981). Venezuelan, eastern, and western encephalomyelitis. In: ''Virus Diseases of Food Animals. A World Geography of Epidemiology and Control''. Disease Monographs, Vol. 2, Gibbs E.P.J, ed. Academic Press, New York, USA, 587-625.

Walton T.E. (1981). Venezuelan, eastern, and western encephalomyelitis. In: ''Virus Diseases of Food Animals. A World Geography of Epidemiology and Control''. Disease Monographs, Vol. 2, Gibbs E.P.J, ed. Academic Press, New York, USA, 587-625.