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[[Category:To Do - CABI]]
Also Known As'''''– Avian reovirus - ARV'''''
Causes – ''Avian infectious tenosynovitis – Chronic viral respiratory disease – Malabsorption syndrome in broilers''
==Introduction==
Avian orthoreovirus is a virus of the '''[[Reoviridae]] family''' and causes '''most importantly [[Arthritis|arthritis]] and [[Tenosynovitis|tenosynovitis]]''' in poultry but can also be a cause of [[Respiratory System|respiratory]] disease.
This disease is not zoonotic.
==Distribution==
Avian orthoreoviruses are '''ubiquitous''' among poultry flocks and have been reported globally.
It is transmitted mainly horizontally via the '''faecal: oral route'''.
Vertical transmission does occur but at low rates.<ref name="Rosenberger">Rosenberger, J. K., Olson, N (1997) '''Viral arthritis.''' In: Calnek, B. W., Barnes, H. J., Beard, C. W., McDougald, L. R., Saif, Y. M eds. '''Diseases of Poultry, edition 10'''. ''Ames, USA: Iowa State University Press'', 711-719</ref>
==Signalment==
'''Young chicks''' are more susceptible than older birds. Age related resistance occurs from 2 weeks of age.<ref name="Rosenberger" />
Tenosynovitis and arthritis are most common in '''broiler/meat breeds''' and also in White Leghorn laying pullets.
==Clinical Signs==
'''Lameness''' is the principle sign of disease, and may be accompanied by '''swelling, haemorrhage, skin discolouration''' and refusal to move. In severe cases, the '''gastrocnemius may rupture''' and so birds may become recumbent and struggle to feed.
'''[[Diarrhoea]], dehydration and anorexia''' can also be caused by the virus (malabsorption syndrome). Neurological signs develop in severe cases. Birds appear soiled and ruffled and may huddle together.
'''Mortality''' in the flock increasing and fluid consumption rising may also be indications of disease.
==Diagnosis==
Diagnosis is often made from the observation of lameness and swollen hock joints.
'''Virus can be isolated''' from the respiratory, enteric and reproductive tracts or from tendons, plasma and blood cells of recently killed birds.<ref> Robertson, M. D., Wilcox, G. E., Kibenge, F. S. B (1984) '''Prevalence of reoviruses in commercial chickens'''. Australian Veterinary Journal, 61(10):319-322; 30</ref>Its site of primary replication is the epithelia of the small intestine. The viruses can then be '''cultured on chicken eggs and chicken embryo liver cell''' cultures. Infection induces formation of '''syncytia, degeneration and holes in the monolayer'''. Presence can be confirmed by '''electron microscopy and PCR'''.
'''Agar Gel Immunodiffusion, Complement fixation and [[ELISA testing|ELISA]]''' can be used to detect antibodies serologically.
On '''post-mortem, the digital flexor tendons, metatarsal extensors and tendon sheaths are inflamed, swollen and surrounded by exudate.''' Cartilage may be eroded and synovial membranes haemorrhagic. '''Fibrosis and adhesions''' develop in chronic cases. On histopathology, '''oedema and synoviocyte hypertrophy and hyperplasia''' are evident.<ref>McNulty, M. S (1993) '''Reovirus'''. Virus infections of birds. 181-193; 97</ref> Visceral damage varies greatly due to the differing capacity of viruses to disseminate.
==Treatment==
'''Vaccination''' can be used in the face of an outbreak. No other treatment options are available.
==Control==
'''Live attenuated and inactivated vaccines''' are available. '''Attenuated vaccines are for use in young birds and inactivated for breeding hens''' which provides maternal protection for chicks. ELISAs can be used to monitor efficacy.
Minimising exposure by '''disinfection, management procedures and strict hygiene protocols''' is also helpful.
{{Learning
|flashcards = [[Avian Orthoreovirus Flashcards]]
}}
==References==
<references/>
Animal Health & Production Compendium, '''Avian Orthoreovirus datasheet''', accessed 03/07/2011 @ http://www.cabi.org/ahpc/
Animal Health & Production Compendium, '''Avian Orthoreovirus infection datasheet''', accessed 03/07/2011 @ http://www.cabi.org/ahpc/
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