NEWCASTLE DISEASE

Also known as Ranikhet is one of the most important diseases of Poultry and birds.In this Article we will discuss about NEWCASTLE DISEASE wholly.

First time recorded
– In 1926 —– in Java (Indonesia) & Newcastle (England)
– In 1927 —– in Ranikhet (India)

Definition

• An infectious, highly contagious & fatal rapidly spreading viral disease
• Chiefly affecting chicken, cage / aviary birds and wild birds
• Characterized by respiratory, digestive, & nervous symptoms (reproductive in layers )
• Marked variation in morbidity, mortality, signs and lesions ( depends on strain of virus )

ETIOLOGY

Newcastle disease virus
• Family: Paramvxoviridae
• Genus: Paramyxovirus (Type 1)
Characteristics:
▪ RNA virus
▪ Enveloped
▪ Agglutinates avian RBCs (HA & HI)
▪ Destroyed by various physical & chemical treatments (acids & alkalis)

VIRAL CLASSIFICATION

On the basis of virulence (Pathotypes)
• Lentogenic (Vaccine Strain) Avirulent to mildly virulent e.g.LaSota , B-1, F, ulster (Immunity is weak & short duration. Needs frequent) revaccination
• Mesogenic:
Intermediate virulent e.g. Mukteswar, Clone 30 (Produce longer and stronger immunity)
• Velogenic (Challenge strain) e.g. Milano, Herts, Texas GB Highly virulent/Pathogenic
On the basis of tissue tropism (predilection sites)
• Neurotropic
• Pneumotropic
• Viscerotropic

TRANSMISSION

Sick birds secrete virus through
– Feaces
– Nasal secretions
– Probably genital secretions
Horizontal
• Between flocks

  • Poultry products – Mechanical vectors
  • Wild birds – Contamination of vaccines
    • Within a flock (3-4days all birds infected)
  • Aerosol – Feed and water – Clothing and foot-wear
    Vertical Not reported

FACTORS IN ESTABLISHING SEVERITY OF DISEASE

• Virus
✓Strain
✓Route of entry
✓Dose
• Host
✓Species
✓Age
✓Immune status
• Co-infection with other organisms
• Stress

CLINICAL SIGNS

Respiratory signs
• Respiratory sounds with sneezing, Gasping & coughing, Copious mucoid nasal discharge
• Edema of tissue around eyes especially lower eyelid
• Cyanosis of comb & wattles

Nervous signs
• Clonic spasm, convulsions
• Torticollis, Opisthotonus
• Drooping of wings
• Paralysis of legs & wings

Enteric signs
• Off feed with Greenish diarrhoea is frequently seen
Mortality —- frequently upto 100%

Viscerotropic velogenic (vvND)

  • Sudden appearance, Spreads rapidly
  • Marked depression and loss of appetite
  • Increased respiratory
  • Sharp drop in egg production (Cessation)
  • Profuse bright green whitish mucoid watery
  • diarrhoea
  • Oedematous swellings of the head and cyanosis of
  • the combs and conjunctivitis in few birds
  • Nervous signs in those that survive initial phase
  • High mortality (>90%) in susceptible flocks

Neurotropic Velogenic

  • Acute respiratory and nervous signs
  • predominate
  • Sudden depression
  • Loss of appetite
  • Drop in egg production
  • Respiratory distress — severe coughing &
  • Gasping
  • Nervous signs — head tremors, wing and leg
  • paralysis, torticollis
  • Mortality rate in adults up to 50-90%. May be
  • much higher in young chickens

Mesogenic

  • Depression and anorexia
  • Weight loss
  • Drop in egg production (lasting 1–3 weeks)
  • Acute respiratory disease with coughing &
  • gasping
  • Nervous signs may develop late in the
  • clinical course
  • Mortality rate about 20-40 %

Lentogenic

  • No major clinical signs
  • Mild respiratory signs
  • Temporary loss of appetite
  • Drop in egg production in layer flocks
  • No nervous signs
  • Negligible mortality unless concurrent
  • disease is present

PATHOGENESIS

• Virus enters in host by inhalation / ingestion
• Attachment of virus to cell receptors (adsorbs)
• Fusion of virus envelop with cell membrane
• Nucleocapsid complex enters the cell
• Virus replication takes place in cytoplasm
• Liberation of virus from host cell
• First viraemia
• Localizes & multiplies in visceral organs
• Second viraemia
• Shedding of virus (6 weeks)

POSTMORTEM LESIONS

Respiratory system
• Haemorrhages in pharynx & trachea
• Catarrhal exudate in nasal passages

Nervous System
• Congestion and oedema of the brain
Digestive system
• Haemorrhages in proventriculus is an
outstanding feature
• Initially haemorrhagic changes followed by
Bluish red raised necrotic areas in lymphoid
follicles of intestine & caecal tonsils which
ulcerate and form ‘Button’ like ulcers

Proventriculus
Trachia of the infected Bird
Greenish Mucoid Watery Diarrhea
New castle disease by vets care
New castle disease by vets care

Lentogenic & Mesogenic ND:

  • Mild conjunctivitis and catarrhal
  • tracheitis

Velogenic ND:

  • Haemorrhage and necrosis of trachea
  • Haemorrhages on tips of proventriculus
  • glands
  • Haemorrhagic and necrotic lesions in
  • entire GIT which ulcerate to form button
  • ulcers
  • Cecal tonsils necrotic & haemorrhagic
  • Haemorrhages on tips of proventriculus
  • glands

DIAGNOSIS

History, clinical signs & necropsy findings
Isolation & identification of the virus (strain)
Sites for sample collection
• Cloacal & tracheal swabs, Lung, Spleen, Liver, kidneys, heart & Brain (important)
• Alimentary tissues ( proventriculus, intestine, caecal tonsil) and respiratory tissues (trachea, lung) for pathogenicity assessment and virus
characterization
Serological and molecular identification
• HA, HI, VN, FAT, ELISA, RTPCR

PREVENTION AND CONTROL

Biosecurity
• Improvement of biosecurity measures
Vaccination ( Eye drops, D/W, Sprays etc)
• Types
– Live vaccine (Attenuated)
– Killed vaccine (Inactivated) Oil based
vaccine
• Vaccination schedule for broilers
– 1st shot —– in 1st week of age
– 2nd shot —- in 3rd week of age
Depends on health status of birds

In case of an outbreak
• No specific treatment
• Supportive therapy
– Vitamin E supplementation
– Treat for secondary bacterial infections
• Provide good quality of feed & water
Public Health
• In man, ND virus may cause influenza-like
symptoms and pink eye (Conjunctivitis)
• Completely destroyed by normal cooking

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