Turkey Rhinotracheitis Virus

Also Known As: Avian Pneumovirus — Swollen Head Syndrome — APV — TRTV — TRV

Introduction

Avian Pneumovirus is a pneumovirus, a type of paramyxovirus causing respiratory disease in turkeys and chickens. It is one of the most important viral respiratory diseases of turkeys.

TRV is not zoonotic.

Distribution

The virus is widespread in Europe. It is known to be present in Asia, Africa, the Middle East South America and North America too.

TRTV can replicate in the reproductive and respiratory systems. Its transmission is mainly oral.

Signalment

Turkeys are generally more susceptible to the disease than chickens, and other domesticated species e.g. pheasants, guinea fowl, are affected. Intensive rearing systems with high stocking density are conducive to spread of the disease.

Clinical Signs

Clinical signs usually begin 3 days after infection but are mild initially. Mortality is highest in turkey poults and is usually due to secondary bacterial infection.

Respiratory disease is most common and causes tachypnoea, nasal discharge, dyspnoea, sneezing and abnormal breathing. Clinical disease is usually accompanied by a decrease in egg production and reproductive failure. Folded egg membranes and egg peritonitis may develop consequentially.

Torticollis, reluctance to move, swelling of the head, face and eyes and head shaking are manifestations of more severe cases.

Lack of growth and retardation will occur in young birds infected by TRV.

Diagnosis

Serological diagnosis can be achieved by ELISA. Indirect immunofluorescence and viral neutralisation can be applied to tissue sections, though detection by RT-PCR is now the most common approach.

Viral isolation can be attempted from nasal turbinates, trachea or exudates, oesophagus and buccal cavity, and is most successful in turkeys.

Necropsy findings can also be suggestive:

Turkeys:

Clear to greyish exudate is present in the nasal turbinates and excess mucus is present in the trachea. Inflammatory exudates is evident microscopically.

In hens, oviductal infection is represented by inspissated albumen forming white masses. Misshapen eggs may be present and ovarian regression evident.

Other fowl

Turbinate mucosae are discoloured red-purple by petechiation. The subcutaneous tissues covering the head are oedematous with fibrinopurulent inflammation. Pericarditis and perihepatitis are regularly seen.

Egg peritonitis is also sometimes found.

Treatment

There is no treatment for the viral infection but antibiotics administered in drinking water may minimise losses by treating secondary bacterial infection.

Control

Vaccines are available against type A and B TRV for both turkeys and chickens, and are the main form of control in endemic countries. Killed vaccines must be first primed with a live vaccine to be effective.

Good biosecurity should always be practised including particular attention to storage and disposal of carcasses on the unit. Air quality should be monitored and maximised and birds of different ages segregated wherever possible.

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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 6 June 2011.