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==Introduction==

==Introduction==

Avian Encephalomyelitis (AE) is commonly known as epidemic tremor in chickens.  It is caused by ''Avian encephalomyelitis-like virus 1'' (AEV)''', which is a single-stranded RNA''' (ssRNA) virus belonging to the [[Picornaviridae| '''''Picornaviridae''''']] family.  It was formerly classified as an ''Enterovirus'' but is now considered a '''''Hepatovirus''''' as its genome shares greater resemblance with that of the ''hepatitis A viruses'' than the other picornavirus genera.  The virus has a non-enveloped capsid with icosahedral symmetry and is approximately 26 nm in diameter and has buoyant density of 1.31 g/ml in caesium chloride <ref>Tannock, G.A., Shafren, D.R., (1994) '''''Avian encephalomyelitis: a review'''''. ''Avian Pathology'', 23(4):603-620; 85 ref.</ref>.  ''Avian encephalomyelitis-like virus 1'' is not related antigenically to other avian ''picoronaviruses'', which is why it has been referred to in the past as an enteroviruses or enterovirus-like viruses.  

Avian Encephalomyelitis (AE) is commonly known as epidemic tremor in chickens.  It is caused by ''Avian encephalomyelitis-like virus 1'' (AEV)''', which is a single-stranded RNA''' (ssRNA) virus belonging to the [[Picornaviridae| '''''Picornaviridae''''']] family.  It was formerly classified as an ''Enterovirus'' but is now considered a '''''Hepatovirus''''' as its genome shares greater resemblance with that of the ''hepatitis A viruses'' than the other picornavirus genera.  The virus has a non-enveloped capsid with icosahedral symmetry and is approximately 26 nm in diameter and has buoyant density of 1.31 g/ml in caesium chloride.  ''Avian encephalomyelitis-like virus 1'' is not related antigenically to other avian ''picoronaviruses'', which is why it has been referred to in the past as an enteroviruses or enterovirus-like viruses.  

Avian Encephalomyelitis (AE) is of economic concern to breeders and layers as it causes a '''decrease in egg production''' in laying hens, a '''decrease in egg hatchability''', '''neurological diseases in chicks under three weeks of age''' and '''affected chicks that survive are considered unlikely to be profitable'''.

Avian Encephalomyelitis (AE) is of economic concern to breeders and layers as it causes a '''decrease in egg production''' in laying hens, a '''decrease in egg hatchability''', '''neurological diseases in chicks under three weeks of age''' and '''affected chicks that survive are considered unlikely to be profitable'''.

Grossly, lymphocytic infiltration of the muscular region of the ventriculus has also been noted as well as perivascular infiltration within the brain and chord, with the exception of the cerebellum, where lesions can be found only in the nucleus cerebellaris.  '''Pathognomonic lesions can be found within the midbrain and rotundua and ovidalis nucleus  (microglisosis)''' and '''proventriculus (dense nodules within the muscular wall)'''.  Lesions can also be present in the pancreas.  

Grossly, lymphocytic infiltration of the muscular region of the ventriculus has also been noted as well as perivascular infiltration within the brain and chord, with the exception of the cerebellum, where lesions can be found only in the nucleus cerebellaris.  '''Pathognomonic lesions can be found within the midbrain and rotundua and ovidalis nucleus  (microglisosis)''' and '''proventriculus (dense nodules within the muscular wall)'''.  Lesions can also be present in the pancreas.  

'''Differential diagnoses''' include [[Newcastle Disease Virus|Newcastle disease (ND)]], nutritional disturbances ([[Rickets|rickets]], encephalomalacia, riboflavin deficiency), and [[Mareks Disease|Marek’s disease]] <ref name="Calnek, 2003">Calnek, B.W.(2003) '''Avian Encephalomyelitis'''. In: Saif, Y.M., Barnes, H.J., Glisson, J.R., Fadly, A.M., McDougald, L.R., Swayne, D.E., eds. Diseases of Poultry. Ames, Iowa, USA: ''Iowa State Press'', 271-282.</ref>

'''Differential diagnoses''' include [[Newcastle Disease Virus|Newcastle disease (ND)]], nutritional disturbances ([[Rickets|rickets]], encephalomalacia, riboflavin deficiency), and [[Mareks Disease|Marek’s disease]].

==Distribution==

==Distribution==

==Treatment==

==Treatment==

There is '''no treatment''' for chicks infected with avian encephalomyelitis.  <ref name="Calnek, 2003" />. Surviving chicks will be '''immune to AE for life'''.

There is '''no treatment''' for chicks infected with avian encephalomyelitis. Surviving chicks will be '''immune to AE for life'''.

==Control==

==Control==

In regions where AE is prevalent, an effective way of preventing AE is to '''vaccinate pullets''' several weeks before they come into lay. Vaccination protects the flock from a reduction in egg production and prevents vertical transmission of the virus to chicks by providing the chicks with a sufficient level of maternal derived antibodies because there is only one serotype for the AEV.  There are live and attenuated vaccinations available which can be administered in '''drinking water''' or as an '''eye drop''', the latter being more effective. Vaccination by eye-drop of only 10% of a flock gave the same results as drinking water application <ref name="Shafren, 1992">Shafren, D.R., Tannock, G.A., Groves, P.J. (1992) '''Antibody responses to avian encephalomyelitis virus vaccines when administered by different routes'''. ''Australian Veterinary Journal'', 69(11):272-275; 10 ref.</ref>

In regions where AE is prevalent, an effective way of preventing AE is to '''vaccinate pullets''' several weeks before they come into lay. Vaccination protects the flock from a reduction in egg production and prevents vertical transmission of the virus to chicks by providing the chicks with a sufficient level of maternal derived antibodies because there is only one serotype for the AEV.  There are live and attenuated vaccinations available which can be administered in '''drinking water''' or as an '''eye drop''', the latter being more effective. Vaccination by eye-drop of only 10% of a flock gave the same results as drinking water application.

==References==

==References==

{{CABI source

{{CABI source

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[[Category:Hepatoviruses]]

[[Category:Hepatoviruses]]

[[Category:Avian Viruses]]

[[Category:Avian Viruses]]

[[Category:Neurological Diseases - Birds]]

[[Category:Neurological Diseases - Birds]]

[[Category:CABI Expert Review]]

[[Category:CABI Expert Review]]