Signs

• Sudden death.
• Marked loss of appetite, reduced feed consumption.
• Cessation of normal flock vocalisation.
• Drops in egg production.
• Depression.
• Coughing.
• Nasal and ocular discharge.
• Swollen face.
• Cyanosis of comb/wattles.
• Diarrhoea (often green).
• Nervous signs such as paralysis.

Post-mortem lesions

• Inflammation of sinuses, trachea, air sacs and conjunctiva.
• Ovarian regression or haemorrhage.
• Necrosis of skin of comb and wattles.
• Subcutaneous oedema of head and neck.
• Dehydration.
• Muscles congested.
• Haemorrhage in proventricular and gizzard mucosae and lymphoid tissue of intestinal tract.
• Turkey lesions tend to be less marked than those of chickens, while ducks may be symptomless, lesionless carriers of highly pathogenic virus.

Diagnosis

A presumptive diagnosis may be made on history and post­mortem lesions. Confirmation is by viral isolation in chick embryo, HA+, NDV-, DID+. Commercial Elisa test kits are now available. However, as with many such tests occasional false positive reactions can occur. The agar gel precipitation test is non-group-specific and is used to confirm any positives. Differentiate from Newcastle disease, fowl cholera, infectious laryngotracheitis, other respiratory infections, bacterial sinusitis in ducks.

Treatment

None, but good husbandry, nutrition and antibiotics may reduce losses. Eradication by slaughter is usual in chickens and turkeys.

Prevention

Hygiene, quarantine, all-in/all-out production, etc. Minimise contact with wild birds, controlled marketing of recovered birds. Vaccination is not normally recommended because, although it may reduce losses initially, vaccinated birds may remain carriers if exposed to the infection. Vaccines have been used in recent outbreaks in Mexico and Pakistan. To be effective inactivated vaccines must be the right subtype for the particular situation (H5 will not protect against H7 and vice versa). In outbreaks a regime of slaughter, correct disposal of carcases, cleaning, disinfection, isolation, 21-day interval to re-stocking should be followed. Survivors can be expected to have a high degree of immunity but may harbour virulent virus.