Newcastle Disease

               [other names : Avian Pneumoencephalitis , Ranikhet disease , Avian distemper ]

• It is a highly contagious viral infection that affects many species of domestic and wild birds to varying degrees.
• Domestic fowl, turkeys, pigeons and parrots are most susceptible while a mild form of the disease affects ducks, geese, pheasants, quail and guinea fowl.
• Characterised by high mortality , nervous sign and hemorrhagic and necrotic lesions in gut mucosa

Etiology :

   Newcastle disease virus of genus Avulavirus of Paramyxoviridae family

      [ single stranded RNA]

Four pathotypes :

1. Asymptomatic enteritis :  subclinical
2. Lentogenic:   subclinical to mild respiratory 
3. Mesogenic : respiratory or neurological
4. Velogenic : 

1. Neurotropic : respiratory or neurological
2. Viscerotropic : hemorrhagic intestinal lesions

• Morbidity = 100%
• Mortality = 90%

Transmission :

• Direct contact with faeces and respiratory discharges
• Contamination of environment
• Feed , water
• Equipment
• Human clothing
• Contaminated / incompletely inactivated vaccine
• Survives for long period in environment
• IP = 2-15 days [ 5-6 days average ]
• Migratory birds , feral pigeons
• Contamination of poultry feed
• Vertical transmission is rare

Pathogenesis :

Entry [ ingestion / inhalation]

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Goes in digestive tract and respiratory route

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First replication occur in mucous membrane of epithelial cells of GIT and respiratory tract

[ trachea , oesophagus , crop , liver, cloaca, gizzard , intestine]

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    Blood [ primary viremia]

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Goes in spleen , bone marrow , etc

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Blood vessels / blood

[ secondary viremia]

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CNS, lungs, back to intestine

[ second replication of virus]

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Pathological signs occur

Clinical signs :

• Sign vary with species and virulence
• Drop in egg production with thin , rough-shelled eggs
• Numerous death within 24-48 hours
• Edema of head , especially around eyes
• Greenish -dark watery diarrhoea
• Respiratory signs
• Gasping
• Coughing
• Nervous sign
• Depression
• Muscle tremor
• Complete paralysis
• Torticollis

Postmortem finding :

• There are no pathognomonic gross lesions; several birds must be examined to determine a tentative diagnosis and final diagnosis must await virus isolation and identification.
• Only velogenic strains produce significant gross lesions 
• Lesions that may be found include:
• swelling of periorbital area or entire head
• oedema of the interstitial or peritracheal tissue of the neck; especially at the thoracic inlet
• congestion and sometimes haemorrhages in the caudal pharynx and tracheal mucosa
• diphtheritic membranes may be evident in the oropharynx, trachea and oesophagus
• petechiae and small ecchymosis on the mucosa of the proventriculus, concentrated around the orifices of the mucous glands
• oedema, haemorrhages, necrosis or ulcerations of respiratory/digestive lymphoid tissue, including cecal tonsils and Peyer’s patches
• oedema, haemorrhages or degeneration of ovaries
• although less evident in older birds, haemorrhages of the thymus and bursa of fabricius may occur
• spleen may appear enlarged, friable and dark red or mottled
• some cases may present pulmonary oedema and pancreatic necrosis

Diagnosis :

• History
• Clinical; signs and lesion
• Virus cultivation : chicken embryo , cell culture, animal inoculation
• Detection of viral antigen :
• PCR & sequencing
• Immunofluorescence
• Immunohistochemistry
• Detection of viral antibody
• ELISA & HI test

Differential diagnosis :

• Fowl cholera
• Highly pathogenic avian influenza
• Laryngotracheitis
• Fowl pox (diphtheritic form)
• Psittacosis (psittacine birds)
• Mycoplasmosis
• Infectious bronchitis
• Aspergillosis
• Also management errors such as deprivation of water, lack of or nutritionally deficient feed and poor ventilation