L3: Newcastle Disease (Romero)

Question 1

Newcastle disease is aka:

Answer 1

Avian paramyxovirus 1

• has 9 serotypes
• a ss RNA virus

Question 2

Membrane of NCD virus contains what glycoproteins?**

Answer 2

HN and F

Question 3

Pathotypes of NCD

Answer 3

Viscerotropic velogenic (gut hemorrhage, high Mo)
Neurotropic velogenic (resp/neuro signs, high Mo)
Mesogenic (acute resp/nervous signs, low Mo)
Lentogenic (mild resp signs)
Asymptomatic enteric (avirulent)

Question 4

Where did NCD come from?

Answer 4

1950: partridges and pheasants imported from Hong Kong

CA outbreaks 1970s, early 200s

Question 5

Pathogenicity assays for NCD by age

Answer 5

1. Eggs: Mean Death Time (MDT)
2. Day old chicks: Intracerebral Pathogenicity Index
3. 6 wk old chickens: Intravenous Pathogenicity Index
4. 6-8 wk old chickens: Intracloacal Inoculation Pathogenicity\

Question 6

NCD: geo distr.

Answer 6

Endemic: Asia, Middle east, Africa, Central/S. America
Epizootic: US, UK, Australia, Canada

Question 7

Epi of NCD

Answer 7

-virus survives for wks in env.
-incubation period = 2-15 days
-migratory birds and feral pigeons can carry
deaths in 24-48 hrs, continuing for 7-10 days
-almost 100% Mb (90% Mt, depending on strain)

Question 8

Trans. Of NCD

Answer 8

• direct contact

- contaminated env.

Question 9

CS of NCD

Answer 9

• dec. egg production
• ducks, geese can be asymptomatic
• edema of head/eyes
• green/dark watery diarrhea
• resp/neuro signs
• depression, prostration
• asphyxia
• hemorrhages in comb, head, conjunctiva

Question 10

Necropsy of NCD

Answer 10

• multifocal hemorrhages (ie. In trachea, larynx, GIT, ova)

- hyperemic/necrotic cecal tonsils and lymphoid patches

Question 11

Public health significance of NCD

Answer 11

Can cause conjunctivitis in humans (goes away in about a week)
-NOT transmitted by consuming poultry products

Question 12

Vax for NCD

Answer 12

At hatchery: in ovo or as spray/eye drops in chicks (live vax)
At poultry house: live vax in drinking water
Layers/repro stock: prime with live vax, boost with inactivated vax at 16-18 wks

High Ab lvls can be transferred to progeny

Question 13

What samples can be collected for dx of NCD?

Answer 13

• feces/cloacal swabs
• tracheal swabs
• brain, when neuro signs present
• LU/SP/LIV/HT

Question 14

Laboratory dx of NCD

Answer 14

• MUST ALWAYS BE CONFIRMED
  1) Ag found in tissues
  2) isolate in SPF embryonated eggs (kills embryo in 3-7 days; test for HEMAGGLUTINATION in 5-7 days)
  3) RT-PCR

Question 15

SPF embryonated chicken eggs are the most sensitive for all APMVs

Answer 15

:)

Question 16

ID of avian paramyxoviruses

Answer 16

Hemagglutination (HA) activity in chorioallantoic fluid due to 1 of 9 paramyxoviruses or 1 of 16 FLU subtypes

-confirm dx by inhibition of HA or HI with specific antisera and/or monoclonal Ab

Question 17

Ddx for NCD

Answer 17

• HPAI**
• Fowl cholera
• Laryngotracheitis
• Coryza
• Fowl pox
• Psittacosis
• Mycoplasmosis
• Infectious bronchitis
• Management problems

Question 18

How to differentiate virulent from non-virulent strains of NCD**

Answer 18

Virulent strains have the presence of basic amino acids around the cleavage site of the Fusion (F) protein

Question 19

NCD vax in BROILERS

Answer 19

• maternal Ab interferes with systemic active immunity
• doesn’t significantly affect local resp. Immunity
• early vaccinations require boosting; hatchery vax is short lived
• immune competence is better in older birds

Question 20

Serological surveillance after NCD vaccination

Answer 20

ELISA is used to assess humoral response after vaccination or natural infections; provides information on uniformity and strength of humoral response