This document discusses infectious bursal disease virus (IBDV) which affects poultry. It begins by describing the virus's characteristics, including that it is a small, non-enveloped double stranded RNA virus with a bi-segmented genome. It then covers the virus's protein structure and the roles of the different proteins. The document discusses how the virus spreads horizontally through infected feces or contaminated equipment. It outlines the virus's epidemiology, describing the natural hosts, ages of highest susceptibility, and pathogenesis. The document concludes by covering treatment and control methods like biosecurity and vaccination programs. It also discusses how extreme vaccination pressure, improper cleaning, and other factors have led to the evolution of more virulent virus strains

1. Infectious Bursal Disease IBD
The Virus

2. Plan of talk
 Virus characteristics
 Virus protein structure
 Spread of virus
 Epidemiology
 Treatment and control
 Evolution of the virus

3. Plan of talk
 Virus characteristics
 Virus protein structure
 Spread of virus
 Epidemiology
 Treatment and control
 Evolution of the virus

4. Virus Characteristics
 Family: Birnaviridae.
 Genus: Avibirnavirus.
 Small, non-enveloped double stranded RNA virus.
 Has a bi-segmented genome.

5. Virus Classification
IBDV strains are classified into two distinct serotypes;
 Serotype 1
 Pathogenic IBDV affecting poultry
classic, very virulent, variant IBDV strains
 Serotype 2
 Apathogenic IBDV.
They are
1. Differentiated by virus neutralization test.
2. There is no cross protection between these two serotypes.

6. Cont. …
Very stable
 The virus survives for:
 122 days in non disinfected house without birds.
 52 days in contaminated water or feed.
 5 hours at 56°C
 The virus resists pH range from 2 to 12

7. Cont. …
Active disinfectants
 Chloramin 2%
 Glutaraldehyde
 Formaldehyde, only if tempreture is > 20°C

8. Plan of talk
 Virus characteristics
 Virus protein structure
 Spread of virus
 Epidemiology
 Treatment and control
 Evolution of the virus

9. VP4 -VP 5
VP1 (Polymerase)
1. Encapsidation of the virus particle.
2. Speed of virus replication.
VP2 (external capsid)
encodes the major antigenic determinants of
the virus, including epitopes that are
important in virus neutralization.
VP5
likely has a regulatory function and
plays a role in B-lymphocyte lysis.
VP4
Is a minor and non-structural
polypeptide.
VP 3 (internal capsid)
Interacts with both VP1 and VP2 and form
VP1-VP3 complexes which is likely to be an
important step in the morphogenesis of IBDV
particles.

10. Cont. …
RoleProtein
Encapsidation of viral particle
VP1
RNA dependant RNA polymerase
Small amount in virus capsids
Contain antigenic region responsible for :
 Serotype specific
 Elicit neutralizing antibodies
VP2
Main capside protein
Morphogenesis of the virus
VP3
Other major structural protein not
exposed at the surface
Viral protease (maturation of VP2 trimming
peptides during virus assumbly
VP4
B-lymphocyte lysis.VP5

11. Cont. …
Key points
 Neutralizing antibodies are formed against VP2.
 Modification of VP2 leads to modification of immunogenic
characteristics of viruses.
 Variant strain:
 Mutation VP2
 No cross neutralisation with classical strains.

12. Plan of talk
 Virus characteristics
 Virus protein structure
 Spread of virus
 Epidemiology
 Treatment and control
 Evolution of the virus

13. Spread of Virus
 IBDV is horizontally transmitted but
not vertically.
 Infected and vaccinated birds usually
shed virus through faces from day 2
till day 10 post infection or
vaccination.

14. Cont. …
Horizontal transmission occurs through:
1. Infected faeces.
2. Contaminated equipment (especially footwear)
3. Other organic material.

15. Cont. …
Lesser mealworm
(Alphitobius diaperinus)
acts as a vector carrying IBDV
from one cycle to the next.

16. Plan of talk
 Virus characteristics
 Virus protein structure
 Spread of virus
 Epidemiology
 Treatment and control
 Evolution of the virus

17. Epidemiology
Natural host:
 Chickens and turkeys are the natural hosts of the virus.
Age:
 Highest susceptibility occures from 3 to 6 weeks of age.
 Mainly calssic strain
 Lowest susceptibility after 9 weeks of age.
 Any infection after 9 weeks would be vv strain
 Infection before 2 weeks cause immunosuppression
without clinical signs.
 Mainly variant strain

18. Cont. …
Oral infection
Persistence
52 days in contaminated water or feed.
Excretion
Day 2-10
post infection

19. Pathogenesis
Other Organs
Spleen, thymus
Oral Infection
Duodenum, jejenum & caecum
Macrophages & lymphatic cells
Liver
Kupffer cells
Bursa of Fabricius
Immature B-lymphocytes
4-5 hrs
5 hrs
16+ hrs
11-13 hrs

20. Plan of talk
 Virus characteristics
 Virus protein structure
 Spread of virus
 Epidemiology
 Treatment and control
 Evolution of the virus

21. Treatment & Control
Fundamental issues
 There is no treatment available.
 Vaccination in the face of outbreak will not be effective.
 Passive immunity protects progeny against disease, breeder
flocks are immunized against IBD with inactivated vaccines to
confer MDA to their progenies.

22. Cont. …
The approach to IBDV control and prevention involves:
1. Biosecurity
2. Vaccination

23. Biosecurity
Important measures to ensure that birds would be competent to
face any disease include:
1. All infected litter and carcasses of infected birds must be
suitably disposed of away from the site or any other
poultry operation.
2. A thorough well planned disinfection regimen must be
implemented.
3. Downtime between successive flocks must be maximized.
(A minimum of 10 days is recommended between
successive broiler flocks.)

24. Vaccination
 Vaccines should cover both classic and variant strains.
 Suggested vaccination program would include:
 Breeders – Use both classic and variant strains.
 Live attenuated vaccines, 2- 3 doses depending on the
challenge.
 Inactivated vaccines – 2 doses.
 Layers
 2 or 3 doses of life attenuated vaccines, may be
intermediate or intermediate plus according to
situation.

25. Plan of talk
 Virus characteristics
 Virus protein structure
 Spread of virus
 Epidemiology
 Treatment and control
 Evolution of the virus

26. Evolution Of The Virus
1. Extreme vaccination pressure.
 Use of cloned intermediate IBD vaccine that confers very
narrow protection.
 Vaccinating breeders with inactivated classic-type virus
only resulting in chicks hatching with maternal antibodies
of limited to the classic type.
2. Short down time between grow-out.
3. Improper cleaning and disinfection.
4. Increased bird population.

27. IBDV
Virus Protein 2

28. VP2
Classic Vs Variant strains

29. IBDV VP2
Classic and Variant Strains
Central cup-shaped
Peak APeak B
Peak 1
Variant Strain
Peak 2
Classic Strain

30. VP2
Chicken embryo Vs Tissue culture propagation

31. IBDV VP2
Field Virus
Amino acids 253
Amino acids 284

32. IBDV VP2
Chicken Embryo Propagation
Amino acids 253
Amino acids 284

33. IBDV VP2
Tissue Culture Propagation
Amino acids 253
Amino acids 284