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Disease Overview
Overview
Newcastle Disease is a highly contagious and globally devastating viral infection caused by the Newcastle Disease Virus (NDV), also known as Avian Paramyxovirus (APMV). It belongs to the Avulavirus genus and affects a wide spectrum of domestic and wild avian species.
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Disease Behavior
Pathogenicity
NDV strains are categorized by their virulence levels:
Velogenic (High Virulence)
Causes severe disease and high mortality.
Viscerotropic Velogenic (VVND)
Often called "Exotic Newcastle Disease," this is the most acute form.
Mesogenic (Intermediate Virulence)
Causes moderate respiratory signs and low mortality in adult birds.
Lentogenic (Low Virulence)
Causes mild or subclinical infections; these strains are primarily utilized in vaccine production.
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Disease Presentation
Clinical Signs
Symptoms vary based on the organ system targeted by the specific strain:
Nervous System
Central nervous system (CNS) dysfunction including ataxia (incoordination), head tremors, circling, and torticollis (twisted neck).
Respiratory System
Gasping, coughing, and hoarseness.
Digestive System
Prodfuse watery diarrhea, often greenish or hemorrhagic.
Production
Severe drops in egg production and the appearance of abnormal, soft-shelled eggs.
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Disease Spread
Transmission & Viral Shedding
The virus is shed in high concentrations through feces and respiratory secretions (nasal, oral, and ocular). It spreads rapidly via:
Direct Contact
Between infected and susceptible birds.
Indirect Contact
Contaminated feed, water, equipment, and clothing (fomites).
Environmental Persistence
The virus can survive for weeks in litter or carcasses, especially in cool, moist conditions, though it is highly sensitive to UV light (sunlight).
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Identification
Diagnosis and Timeline
Incubation
Generally 2–6 days, but can extend to 21 days in some cases. In highly virulent outbreaks, sudden death may occur within 72 hours.
Diagnosis
Definitively confirmed through laboratory testing. This includes virus isolation (egg inoculation), RT-PCR for viral genetic material, and monitoring significant rises in antibody titers via serology (HI test).
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Farm Protection
Prevention & Control
✓
Biosecurity: Strict movement control and excluding wild birds (potential carriers like waterfowl).
Symptoms to Monitor
Clinical Signs
Head tremors
Head tilt
Twisted neck (torticollis)
Incoordination
Convulsions
Circling
Muscle spasms
Head shaking
Unilateral or bilateral, partial or complete leg or wing paralysis
Diarrhea, sometimes with blood
Respiratory distress
Hoarseness
Gasping
Reduced appetite
Lethargy
Fluffed up feathers
Reduced egg production
Abnormal eggs
Falling off perch
