Turkey Rhinotracheitis Virus
Also Known As: Avian Pneumovirus — Swollen Head Syndrome — APV — TRTV
Introduction
Turkey Rhinotracheitis Virus is a 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 thought to be present in Asia, Africa, South America and North America too.
TRTV can replicate in the reproductive and respiratory systems. Its transmission is mainly oral.
Signalment
Turkeys appear most susceptible to the disease although other domestic fowl can be infected. 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.
Viral isolation can be attempted from nasal turbinates, trachea or exudates and is easiest 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 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
Animal Health & ProductIon Compendium, Turkey Rhinotracheitis Virus datasheet, accessed 06/06/2011 @ http://www.cabi.org/ahpc/
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