Avian Orthoreovirus

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 and tenosynovitis in poultry but can also be a cause of 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.

Signalment

Young chicks are more susceptible than older birds. Age related resistance occurs from 2 weeks of age.

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 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.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 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. 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.

Avian Orthoreovirus Learning Resources
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References

This article was originally sourced from The Animal Health & Production Compendium (AHPC) published online by CABI during the OVAL Project. The datasheet was accessed on 03 July 2011.