Diseases: Newcastle Disease

Introduction

• One of the two most important viral diseases of domestic chickens. The other is highly pathogenic avian influenza which, to date, occurs rarely in village chickens.
• Virus strains vary in virulence from extremely mild to highly virulent

 

Clinical Signs

• All ages affected
• Lethargy, weakness, gasping and coughing
• Diarrhoea, with faeces often green
• Paralysis, muscle tremors and twisted necks in chickens that survive for some days
• Mortality rate up to 100%

 

Post Mortem Lesions

• None if the chickens die rapidly
• Haemorrhages in parts of the intestinal tract, especially proventriculus, caecal tonsils and lymphoid accumulations in the small intestine
• Haemorrhages and congestion in trachea with some strains of virus

 

Diagnosis

• Consideration of clinical signs and gross lesions
• Isolation of virus in embryonated eggs

 

Samples

• Organs with lesions, brain (transport the entire head), bone marrow (transport long bones), spleen, lung
• Keep samples cold as virulent viruses are readily inactivated by heat

 

Transmission

• Highly infectious – in faeces, secretions from nose and mouth, and expired air
• Infected birds excrete the virus before showing clinical signs
• Outbreaks often originate with the introduction of infected birds
• Contaminated feed, water, implements, people, clothing may spread the virus

 

Treatment

• There is no specific treatment for Newcastle disease
• Local remedies usually not effective

 

Prevention and Control

• Bury dead birds, or remains from dead birds
• Do not introduce new chickens into a flock when the disease is occurring
• Vaccinate chickens - thermostable vaccines are being produced especially for use in village chickens