Avian Influenza Diagnosis

Clinical diagnosis:

Clinical signs in affected birds are often indicators of the disease and should be recorded in the epidemiological enquiry form (Annexure I).

Low pathogenic strains

• - Mild to severe respiratory symptoms.
• - Decrease in egg production up to 45% (takes 2 - 4 weeks to recover)
• - Mortality 3% (layers), 15% (broilers).

Highly pathogenic strains

• - Severe respiratory distress, depression, ruffled feathers.
• - Watery eyes and sinuses.
• - Cyanosis of combs, wattles and shanks.
• - Edema of head and sinuses.
• - Diarrhea (initially bright green later white).
• - Nervous signs as with highly virulent Newcastle (Ranikhet) Disease.
• - Sudden death (within 24 hrs of first signs), mortality can approach 100%.

HPAI virus needs to be differentiated from Newcastle disease, Infectious laryngo-tracheitis (ILT), fowl cholera (caused by Pasteurella multocida) and other diseases which induce similar clinical signs at times.

Differential Diagnosis:

Post mortem lésions:

Gross lesions:

In per-acute cases (day 1 & 2), death occurs without gross lesions. Generally, congestion, hemorrhage and edema are found in internal organs. In acute cases (day 3 –5), the following lesions are observed:

• - Subcutaneous edema of head and neck.
• - Conjunctivae congested and petechiated.
• - Abdominal fat, serosa, peritoneum with pinpoint haemorrhages.
• - Diffuse haemorrhages between hock and feet and thigh muscles.
• - Petechiation of whole viscera.
• - Air sacculitis, peritonitis (cattarhal, fibrinous).
• - Atrophy of lymphoid organs.

Histopathological lesions:

• - Perivascular cuffing (PVC) of lymphocytes in brain, heart, spleen, pancreas.
• - Coagulative necrosis in kidney, lungs, spleen.
• - Edema, hyperaemia, hemorrhage in heart muscles.
• - Necrotic epithelial and urate casts in kidney tubules.

Links to other information resources of Avian Influenza

• For Laboratory Diagnosis of AI, please refer to Lab Diagnosis of AI
• For guidelines to send samples of AI to NIHSAD, please refer to Annexure II
• For detailed information about control of AI in India, please download the Action Plan, 2006 prepared by DADF, Ministry of Agriculture, Govt. of India.
• Collection and shipment of Avian Influenza samples to NIHSAD
• For general guidelines about collection and shipment of diagnostic specimens, please refer to OIE 2008 manual- chap. 1.1.1