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IBD_The Virus

"عسى أن تكون علما ينتفع به"
Poultry Gumboro
Infectious bursa disease
IBDV

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IBD_The Virus

  1. 1. Infectious Bursal Disease IBD The Virus
  2. 2. Plan of talk  Virus characteristics  Virus protein structure  Spread of virus  Epidemiology  Treatment and control  Evolution of the virus
  3. 3. Plan of talk  Virus characteristics  Virus protein structure  Spread of virus  Epidemiology  Treatment and control  Evolution of the virus
  4. 4. Virus Characteristics  Family: Birnaviridae.  Genus: Avibirnavirus.  Small, non-enveloped double stranded RNA virus.  Has a bi-segmented genome.
  5. 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. 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. 7. Cont. … Active disinfectants  Chloramin 2%  Glutaraldehyde  Formaldehyde, only if tempreture is > 20°C
  8. 8. Plan of talk  Virus characteristics  Virus protein structure  Spread of virus  Epidemiology  Treatment and control  Evolution of the virus
  9. 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. 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. 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. 12. Plan of talk  Virus characteristics  Virus protein structure  Spread of virus  Epidemiology  Treatment and control  Evolution of the virus
  13. 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. 14. Cont. … Horizontal transmission occurs through: 1. Infected faeces. 2. Contaminated equipment (especially footwear) 3. Other organic material.
  15. 15. Cont. … Lesser mealworm (Alphitobius diaperinus) acts as a vector carrying IBDV from one cycle to the next.
  16. 16. Plan of talk  Virus characteristics  Virus protein structure  Spread of virus  Epidemiology  Treatment and control  Evolution of the virus
  17. 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. 18. Cont. … Oral infection Persistence 52 days in contaminated water or feed. Excretion Day 2-10 post infection
  19. 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. 20. Plan of talk  Virus characteristics  Virus protein structure  Spread of virus  Epidemiology  Treatment and control  Evolution of the virus
  21. 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. 22. Cont. … The approach to IBDV control and prevention involves: 1. Biosecurity 2. Vaccination
  23. 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. 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. 25. Plan of talk  Virus characteristics  Virus protein structure  Spread of virus  Epidemiology  Treatment and control  Evolution of the virus
  26. 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. 27. IBDV Virus Protein 2
  28. 28. VP2 Classic Vs Variant strains
  29. 29. IBDV VP2 Classic and Variant Strains Central cup-shaped Peak APeak B Peak 1 Variant Strain Peak 2 Classic Strain
  30. 30. VP2 Chicken embryo Vs Tissue culture propagation
  31. 31. IBDV VP2 Field Virus Amino acids 253 Amino acids 284
  32. 32. IBDV VP2 Chicken Embryo Propagation Amino acids 253 Amino acids 284
  33. 33. IBDV VP2 Tissue Culture Propagation Amino acids 253 Amino acids 284

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"عسى أن تكون علما ينتفع به" Poultry Gumboro Infectious bursa disease IBDV

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