Poultry Lecture 1: Newcastle disease virus

Question 1

how is Newcastle disease virus grouped?

Answer 1

According to Beard and Hanson grouping which is based on the disease caused

1. Velogenic
   2 types:
   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.

2. Mesogenic
   respiratory and neurological signs, low mortality
3. Lentogenic
   mild infections of respiratory tract only
4. Asymptomatic enteric
   avirulent infection, primary replicatin in the gut. – still comes abck as positive to NDV but no symptoms

Question 2

General Clinical signs NDV

Answer 2

Same as AI

loss of appetite
 abnormal thirst
 dehydration
 emaciation
 ruffled feathers
 Huddling
 Listlessness
 depression
Dull depresses, lethargic

Question 3

Neurotrophic NDV clinical signs

Answer 3

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
Dull depresses, lethargic

Question 4

Lentogenic NDV

Answer 4

This is pneumotrophic (response)

mild rales and snick
 sneezing and coughing
 nasal discharge
 laboured breathing
 open mouth breathing
 head shaking
 greenish-yellow diarrhoea
 and related post mortem lesions
Dull depresses, lethargic

Severe congestion lungs on PM
Tracheal exudate

Question 5

Clinical signs viscerotrophic NDV

Answer 5

Remember this one is high mortality
A type of Velogenic NDV

greenish-yellow diarrhoea
haemorrhage of intestinal tract (blood in faeces)
haemorrhage and related post mortem lesions
proventriculus
lymphoid tissues

Dull depresses, lethargic

Question 6

General PM findings of NDV

Answer 6

Mottled spleen (round is normal in bird)
Lymphoid haemorrhage
Caecal harmorrage
Proventricular haemorrhage

Question 7

diagnosis NDV

Answer 7

Clinical signs, long differential diagnosis… previous flash cards

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)

Sample: trachea, lungs, proventriculus, caecal tonsil, brain

PCR = 90% virus isolates

Question 8

What happens after lab diagnosis of NDV?

Answer 8

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

Question 9

How do we control and prevent NDV?

Answer 9

1. Prevent NDV entering your farm/area – notifiable disease list!
2. If in farm then use biosecurity protocols to keep virus away from farm
3. Increase flock resistance by good management: less stress, better nutrition, avoid/minimise immunosuppression but having good control on other diseases

Question 10

NDV vaccination

Answer 10

Strength flock with vaccination
Unlike avian flue, although notifiable we have vaccines allowed in UK

Live or inactivated

Question 11

UK NDV in broiler farm

Answer 11

Live vaccine given 1-2 times

However in UK normally broiler not vaccinated as by 4/5 weeks they are off to slaughter anyway

Also MDA (think?) protection for first 7-10 days of life

Question 12

UK NDV in egg laying farm

Answer 12

Layers when being reared = live vaccine 1-4 times
1 = Inactivated vaccine
at 15 weeks old transferred to egg laying farm

Question 13

UK ND vaccination breeders

Answer 13

Same as egg laying for the live vaccines
1-4 live
but 1 OR 2 inactivated