Topic 60 - Infectious bursal disease Flashcards
Causative agent of infectious bursal disease
Avibirnavirus genus, Birnaviridae family
Are birniviridae RNA or DNA virus?
RNA
Are birnaviriade enveloped or non-enveloped?
non-enveloped = high resistance
How many segments does birnaviridae have?
Two genome segments, A and B
How many structural protein does birnaviriade have? Name them:
4 structural proteins
1. VP2
2. VP3
3. VP4
4. VP5
Species susceptible for infectious bursal disease:
chickens
But also:
Pheasant, turkey and ostrich
Age susceptible for infectious bursal disease:
3-6 week old
Is infectious bursal disease a acute or chronic disease?
acute
What does infectious bursal disease cause?
inflammation of the bursa of fabricus, which cause sevre immunosuppression
Occurence of infectious bursal disease:
Worldwide
Found at every large chicken farm
Does infectious bursal disease have more than one virulence variants?
yes
How many serotypes does infectious bursal disease have?
two
Serotype 1 and serotype 2
which of the two serotypes of infectious bursal disease, are pathogenic?
Serotype 1
Are there cross-reaction between the two serotypes in infectious bursal disease?
yes, but no cross-reaction
How long can infectious bursal disease survive, and where does it survive after being shed?
in litter up to 6 months
Which solutions kan kill the virus?
- Chlorine + aldehydes
- 0.05% NaOH + detergents at 40 degree
How can propogate infectious bursal disease?
- Embryonated egg
- Cell culture
How many vaccine strains are there for infectious bursal disease?
2
Hot, intermediate and mild
How many antigenic variants of serotype 1 of infectious bursal disease?
VP2 and VP3
What is the VP2 of infectious bursal disease?
It is the virus neutralising antigen of the virus. So the antibodies are able to neutralise the virus. It will be produced against the viral protein
Most important!!
What is the VP3 of infectious bursal disease?
It is sero-and group specific and it will cross react with antigens
Also important, but VP2 is most important
Route of transmission in case of infectious bursal disease:
Per os mainly
But can also go through the conjunctival and be air-borne as well
Is infectious bursal disease contagous?
YES, very!!
How early can infectious bursal disease be shed?
As early as 1 day after infection, but can be detected for 2 weeks in faeces
What is the main source of infection in case of infectious bursal disease?
contaminated environement, through contaminated feed or drinking water
What could be another source of infection in case of infectious bursal disease?
Mechanical transmission between farms and stables, through vehicles, people, clothes etc
Is there a germinative infection for infectious bursal disease?
not yet been confirme, BUT!! The egg-shell is contaminated with faeces
Pathogenesis of infectious bursal disease:
Infection leading to first replication, causing primary viraemia. The virus goes to the liver and reaching the bursa of Fabricius and we will have a secondary viraemia and the virus will be spread through the body
Site of first replication in case of infectious bursal disease:
Macrophages in the gut and lymphoid tissue
What are the main target cells in case of infectious bursal disease?
premature b-cells and other bursal disease
What will happen to the premature B-cells once infectious bursal disease reaches them?
The virus will kill the B-cell “factory” of chickens, and the B-lymphocytes will not mature. This is why we have a immunosuppression
At which age is the activity of the bursa fabricius the highest?
at 2-8 weeks of age
Mortality rate in case of infection of infectious bursal disease in 0-3 weeks of age:
0-30%
Mortality rate in case of infection of infectious bursal disease in 2-8 weeks of age:
5-100%
outcome of infectious bursal disease in 0-3 weeks of age:
Permanent immunosuppression
Outcome of infectious bursal disease in 2-8 weeks of age:
If survive = immuno-competence after recovery
Clinical signs in chickens over 8 weeks of age in case of infectious bursal disease:
no clinical signs
What can we expect if there is a infectious bursal disease infection at a young age?
Damage of B-cell receptor expression, causing a weak immune response against other antigens and we can expect inefficient vaccinations
Factors influencing the severity of infectious bursal disease:
- Age
- Level of maternal antibodies
- Breed of the chicken
- Virulence of the virus strain
- Antigenicity of the virus
- Immunosuppression
Incubation time of infectious bursal disease:
2-3 days
At which age can we see clinical signs in case of infectious bursal disease?
3-6 week of age
Clinical signs in 3-6 week old chickens in case of infectious bursal disease:
- Fever
- ruffled feathers
- Watery diarrhoea
- Swollen, bloody-stained stunt
- Anaemia
- Cyanosis can be observed
Can there be subclinical form of infectious bursal disease? if yes, what is the outcome?
Immunosuppression
Consequences of subclinical form and immunosuppression of infectious bursal disease:
- Retarded growth
- Decreased food consumption
- Ineffective vaccinations
- Clinical signs of other diseases may change
Which organs are pathologically affected in acute phase of infectious bursal disease?
- Bursa of Fabricius
- Spleen
- Liver
- Thymus
- Bone marrow
- kidney
Pathological signs in bursa of fabricius in acute phase of infectious bursal disease:
- Oedema
- Inflammation
- Haemorrhages
- Caseous exudate
Pathological signs in spleen in acute phase of infectious bursal disease:
- Enlarged
- Haemorrhages
Pathological signs in kidney in acute phase of infectious bursal disease:
- nephtirits
Pathological signs in liver in acute phase of infectious bursal disease:
- Oedema
- Dystrophy
- necrotic foci
Pathological signs in thymus in acute phase of infectious bursal disease:
- Lymphoid depletion in the cortex and medulla
Pathological signs in bone marrow in acute phase of infectious bursal disease:
- Necrosis
Which organs are pathologically affected in chronic phase of infectious bursal disease?
bursa of fabricius
Pathological signs in bursa of fabricius in chronic phase of infectious bursal disease:
Atrophy and early involution
How do we diagnose infectious bursal disease?
By age, clinical signs and pathology we will have a good diagnosis.
But we have to detect which virus:
Which laboratory work do we do to detect virus in case of infectious bursal disease?
RT-PCR
In infectious bursal disease, what is very important to differentiate in laboratory work and how is it done?
Differentiate between wild-type and vaccine strain, this is done with RT-PCR og sequencing
Why is serology important in infectious bursal disease?
So supply with information of which antibody level the animal have in regards to vaccination
Differential diagnosis of infectious bursal disease:
- Newcastle disease
- Bacterial septicaemia
- Chicken anaemia
- Coccidiosis
Prevention of infectious bursal disease:
- Hygiene and epidemiological measures
- Prevention of infection in the first two months (because this is the most susceptible age)
- Vaccine
How to prevent infectious bursal disease in the first two months?
- Disinfection of the egg shell
- Decontamination of fomites
- Cleaning and disinfection of stable
- All-in-all-out
How do we determine the timing of vaccination for infectious bursal disease:
Based on the maternal antibody level of the flock. To measure we can use a virus neutralising essay or ELISA
Type of vaccine used for infectious bursal disease:
- live, attenuated vaccine
- Inacitvated vaccine
- Recombinant HVT vector
- immune-complex vaccine
Live, attenuated vaccine for infectious bursal disease:
3 different levels of vaccine: mild, intermediate and strong strains
Recombinant HVT vector vaccine of infectious bursal disease:
- Efficient at high maternal antibody levels (can be used at an earlier time)
- Constant antigen stimuli
- safe
Immuno-complex vaccine of infectious bursal disease:
Live virus are used in combination with specific antibodies
Inactivated vaccine of infectious bursal disease:
- Usually for booster vaccine
Route of application for live attenuated vaccine of infectious bursal disease:
per os, mainly in the drinking water
Route of application for recombinant vector vaccines of infectious bursal disease:
In ovo or SC in the hatchery
Route of application for immune-complex vaccines of infectious bursal disease:
In ovo or SC in the hatchery
Propagation area of live attenuated vaccine of infectious bursal disease
Propagates in the bursa
Propagation area of immune-complex vaccine of infectious bursal disease
NO propagation in the bursa
Propagation area of recombinant vector vaccine of infectious bursal disease
Vaccine STRAIN propagates in the bursa