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Maedi-Visna
Also know as: '''''Maedi-Visna — Lymphoid Interstitial Pneumonia'''''
== Introduction ==
This disease is caused by a [[:Category:Retroviridae|retrovirus]] and affects sheep worldwide. It was originally seen in Iceland, hence the name is Icelandic in origin. The disease is slow to progress and is therefore only seen in sheep greater than 2 years old.
There occurs a primary replication in '''lung macrophages '''and these then carry infection to '''brain, lung, udder and/or joints.''' T cells react causing a '''Type IV immune complex disease. '''Target organs become chronically inflamed after 2-6 years.
'''Visna''' is the '''demyelination''' with '''subacute meningitis''' around ventricles and choroid plexus caused by inflammation. '''Posterior paresis''' progresses for up to a year until sheep can no longer stand.
'''Maedi''' is the lung part of the complex, with alveolar septa becoming infiltrated by [[lymphocytes]] and [[macrophages]], there is also smooth muscle hypertrophy. All these result in a loss of condition.
Transmission of the disease is via aerosol, milk or colostrum and therefore there is increased risk of spread of the disease during winter housing.<br>
Transmission of the disease is via aerosol, milk or colostrum and therefore there is increased risk of spread of the disease during winter housing.
== Clinical Signs ==
Lack of condition/weight loss, lameness and paresis. Coughing, harsh lung sounds on auscultation, increased respiratory rate and nasal discharge also occur with the respiratory part of the disease complex.
== Diagnosis ==
Clinical signs and history can lead to a presumptive diagnosis of the disease. Due to the clinical signs, sheep affected are usually humanely destroyed.
A post mortem examination can be performed which will show lungs that are heavy, rubbery and do not collapse. Grossly, they will show signs of severe [[Interstitial Pneumonia|interstitial pneumonia]] and the impressions of the ribs will remain on the surface fo the lungs after removal from the body. They will appear a mottled, grey colour and speckling may also be present. The diaphragmatic lobes are usually the most severely affected. Bronchial and mediastinal lymph nodes are often enlarged.
Serology can be used on the live animal to detect antibody or antigen by [[ELISA testing|ELISA]].
== References ==
Bridger, J and Russell, P (2007) '''Virology Study Guide''', ''Royal Veterinary College''.
Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) '''Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses''''' Elsevier Health Sciences''
[[Category:Lentiviruses]] [[Category:Sheep_Viruses]] [[Category:Expert_Review]] [[Category:Respiratory_Viral_Infections]] [[Category:Respiratory_Diseases_-_Sheep]] [[Category:Neurological_Diseases_-_Sheep]]
[[Category:Lentiviruses]] [[Category:Sheep_Viruses]] [[Category:To_Do_-_Review]] [[Category:Respiratory_Viral_Infections]] [[Category:Respiratory_Diseases_-_Sheep]] [[Category:Neurological_Diseases_-_Sheep]]