Poultry rest disease: Newcastle disease Flashcards
morphology of ND
HN spikes and F glycoprotein on envelope
Non-segmented genome
Single serotype
No antigenic shift
Point mutations and antigenic drift occur
How is ND grouped?
into 4 groups: bases on what is the major clinical sign
Velogenic (2 subgroups) - severe disease (viscerotropic-velogenic and neurotrophic velogenic)
2. Mesogenic
3. Lentogenic
4. Asymptomatic enteric
Talk about Velogenic ND
2 sub groups: severe disease
Viscerotropic-Velogenic: (visceral tissues) acute lethal infection, gut haemorrhagic lesions. V virulent high mortality
Neurotropic-velogenic: respiratory and neurologic disease, gut lesions absent, high mortality.
Talk about mesogenic ND
respiratory and neurological signs, low mortality.
Talk about Lentogenic ND
: mild infections of respiratory tract only
Talk about Asymptomatic enteric ND
avirulent infection, primary replicatin in the gut. – still comes abck as positive to NDV but no symptoms
General signs of ND, whether vasogenic, mesogenic or lentogenic…
loss of appetite abnormal thirst dehydration emaciation ruffled feathers Huddling Listlessness depression
Neurotropic-velogenic NDV clinical signs
head tremors star-grazing twisted neck convulsions incordination paralysis of wings/legs and related post mortem findings Not reported in UK since 2006, need to keep eye on though
Pneumotrophic NDV
Resp form
mild rales and snick sneezing and coughing nasal discharge laboured breathing open mouth breathing head shaking greenish-yellow diarrhoea and related post mortem lesions
on PM = severely congested lungs and nose exudate and tracheal exudate
Clinical signs of viscerotrophic NDV
greenish-yellow diarrhoea
haemorrhage of intestinal tract (blood in faeces)
haemorrhage and related post mortem lesions
proventriculus
lymphoid tissues
Dull depressed lethargic birds
in 5-10 days = dead
drop egg production
PM Mottled spleen (round is normal in bird) Lymphoid haemorrhage Caecal harmorrage Proventricular haemorrhage Caecal tonsil Aggregated lymphoid tissue haemorrhage
How do we diagnose NDV
Clinical signs, long differential diagnosis…
Serology [HI preferred, ELISA common] blood samples and send for HI (haemoglutination inhibition is used to titrate the antibody response to a viral infection)
Live birds – Oropharyngeal swabs, for Virus Isolation but mostly for RT-PCR
Post-mortem
Lesions (in the proventriculus, intestine) not pathognomonic (just suggestive)
Samples taken at PM:
Trachea - Proventriculus
Lungs - Caecal tonsil
Brain
For virus isolation or PCR. 95% diagnostic method = PCR
How do we do lab diagnosis of ND
Samples prepared then
Egg inoculation
If positive then
Pathogenicity index: Intra Cellular Pathogenicity Index & Intra Venous Pathogenicity Index (in chicks)
So that we can group that specific isolate according to beard and hanson
Some cases we have Monoclonal antibodies to differentiate poultry against pigeon
RT-PCR
If Positive: Virulence determination
sequencing of gene for fusion protein and amino acid read to assess if highly virulent or not
How do we control NDV and prevent: non medical
Prevent NDV entering your farm/area – notifiable disease list!
If in farm then use biosecurity protocols to keep virus away from farm
. Increase flock resistance against NDV in case exposure…
By… good management (less stress, better nutrition, better protection against immunosuprpressive disease
Means more immunocompetatn flocks
Vaccines
Strength flock with vaccination
Unlike avian flue, although notifiable we have vaccines allowed in UK
Live and inactivated
How do we vaccinate broilers against ND
In broiler applied 1-2 times) In UK normally broiler not vaccinated As by 4/5 weeks = sold to slaughter already = short duration MDA from mother first 7-10 days Not much problem for broilers to NDV
