The most important points in NEWCASTLE disease -

 

The most important points in NEWCASTLE  disease .

The other names to newcastle disease :

1- Avian pneumo encephalitis .

2-pseudo fowl pest .

3-pseudo poultry plague .

4-Ranikhet disease .

5-Avian distemper.

Definition of newcastle disease :

It is an acute  contagious disease of wild and domestic birds characterized by respiratory signs and nervous or gastrointestinal signs .

 Etiology of newcastle disease:

It is avian paramyxo virus type -1 which belongs to family paramyxo viridae (APMV-1)

NB: there are from 1 to 9 types of paramyxovirus , the type is according to sequence  of (HN) haemagglutinin neuraminidase  and (F) protein in surface of virus .

Characters of newcastle disease virus :

1- RNA virus .

2- cause agglutination to avian RBCs.

3-sensitive to sun light ( ultra violet rays and dehydration cause destroying virus ).

4-enveloped .

5-sensitive to phenol , ether and formalin .

6-has HN protein which is important in serological identification.

7-has F protein which is responsible for pathogenesis of virus .

8-inactivated in 3 hours at 56 C or 30 minutes at 60 C .

NB: viruses cause agglutination RBCs are avian influenza virus , newcastle disease virus and infectious bronchitis .

NB:bacteria causing agglutination RBCs is mycoplasma .

Virus classification :

according to the vigilance 

1-lentogenic 

2-mesogenic 

3-velogenic 

according to the tropism 

1-pneumotropic (lung )

2-nervotropic (nervous system )

3-viscerotropic (gastro intestinal tract )

NB: respiratory symptoms may be associated with nervous of gastrointestinal signs .

Propagation and multiplication of NDV :

1-egg inoculation .

chicken embryo 9-11 days old in allantoic route .

2-cell culture .

give cytopathic effect (plaque formation )

3- inoculation of non vaccinated susceptible bird .

Economic importance:

1-cost of vaccination .

2-high mortality rate .

3-decrease in egg quantity and quality .

susceptibility:

all types of birds are susceptible but some species are ill and another are carriers only asymptomatic .chickens , turkey and pigeon are high susceptible to disease and appear symptoms while water fowls and wild bird are asymptomatic. newcastle disease is zoonotic disease cause pink eye disease in human .

mode of infection and transmittion :

1- ingestion and inhalation .

bird shed virus in feces and respiratory secretion for 2 weeks after infection .

2-transmitted on fomits .

3-wild birds .

may be reservoir host to lentogenic virus.

4-contamination of vaccine .

Incubation period:

7-15 days depend on immunity of susceptible bird and virulance of  strain .

clinical signs :

In chickens : 

lentogenic strain causes mild  respiratory symptoms  as gasping , sneezing and  coughing or subclinical disease .

mesogenic strain  causes acute respiratory and nervous signs but mortality rate is low .

velogenic strain causes 

1-respiratory signs 

gasping , sneezing , coughing and nasal discharge .

conjunctivitis , swelling area around eyes and cyanosis of comb and wattle.

2-nervous signs 

torticollis , dropping wings , paralysis legs and wings , convulsion and muscle tremors .

3-enteric signs

greenish diarrhea .

4-other signs 

decrease in egg production  , weight gain and quality of egg.

forms of newcastle disease 

1-doyle’s form (VVND)

Acute lethal infection of all ages .

Hemorrhage of the digestive tract mixed with greenish diarrhea .

Very virulence  newcastle disease . 

Velogenic strain .

2-beach’s  form(VVND)

Acute often lethal infection of all ages .

Respiratory and neurologic signs .

Very virulence newcastle disease .

Velogenic strain .

3-beaudette’s form

less pathogenic from VVND .

It is characterized by death in young birds due to mesogenic pathotype and used as secondary vaccine .

 

4-hitchner’s form 

It represented by mild respiratory infections lentogenic pathotype which used as live vaccine .

5-asymptomatic form

gut infection with lentogenic strain .

In pigeon and doves :

digestive , respiratory and neurologic signs but less in severity .

In water fowls (ducks and geese ):

Mostly sub clinical infection in duck and geese .

post mortem lesions of newcastle disease :

1-respiratory system 

-hemorrhage in trachea and pharynx  and cattarhal exudate in nasal passage  .

-thickening air sac and filled of caseous exudate (whitish material )

2-nervous system

-congestion and edema in brain .

3-gastrointestinal tract 

-blue red raised  necrotic areas in lymphoid follicle in intestine .

-hemorrhage in cecal tonsils .

-hemorrhage in proventriculus .

-congested ovary .

Diagnosis of newcastle disease :

1-case history 

-the time of appearance signs or mortality .

-if birds are vaccinated or not .

-if present greenish diarrhea .

2-clinical signs 

3-post mortem lesions 

4-laboratory diagnosis 

Laboratory diagnosis

1-sampling

trachea , lung or brain or tracheal or cloacal swap.

2-isolation of virus 

as in propagation 

egg inoculation 

cell culture 

inoculation in non vaccinated susceptible bird 

3-identification of virus

-HA (haemagglutination test ) then HI ( haemagglutination inhibition )

-PCR 

-serological identification by ELISA (enzyme linked immuno sorrbant assay) or HI  

4-identification of pathogenecity

a) MDT (the mean death time )

inoculation in chicken embryo , if death occur after 48 hours , it is velogenic strain and if death occurs after 4 days , it is mesogenic strain and if death not happens , it is lentogenic strain .

b) ICPI (the intra cerebral pathogenicity index )

inoculation intracerebral in one day old chick 

c)IVPI ( the intravenous pathogenecity index )

intravenous injection in 6 weeks of non vacinated susceptible chicken .

Differential diagnosis 

diseases causes the same respiratory symptomes :

virus diseases : AI (avian influenza ) , IB (infectious bronchitis ) and ILT (infectious laryngotracheitis ) .

bacterial disease : CRD (chronic respiratory disease ) and IC (infectious coryza ).

disease cause he same nervous signs :

vitamin E deficiency and avian encephalomyelitis .

diseases cause hemorrhage in digestive tract :

coccidiosis .

prevention and control of newcastle disease 

a)improvement bio-security measures 

b)vaccination

at age 1-4 day ---- give live vaccine (by eye drop , drinking water or spray )

at age 7-10 day ---injection killed or inactivated vaccine 

at age 14-15 day ---give live vaccine by eye drop

control of an outbreak:

use emergency vaccine .

supportive therapy .

vitamin  E supplement .

treatment secondary bacterial infection .

provide good quality food and water