Presentation on theme: "Infectious Bronchitis"— Presentation transcript:
1Infectious Bronchitis First reported by Schalk & Hawn in 1931 in NorthDakota (USA) in young chicks showing respiratorysignsDistribution: WorldwideTransmission: Horizontal, direct contactIncubation period: hours.
2Infectious Bronchitis Agent: Coronavirus (RAN)Host: Chickens of all agesAffects:respiratory tracturo-genital tract* The virus can be isolated from different organs upto ± 50 d.p.i.
3Infectious Bronchitis Pathogenesis:Young birds:respiratory signssneezing, coughing, nasal discharge.Mortality may reach 30%, especiallyin combination with secondary infections(E. coli, M. gallisepticum).Adult birds:egg dropsalteration in the internal and external quality of eggs(misshapen and soft eggs, watery albumen).
4? Why is IB still a problem? Highly infectious Persistent in the birds Fast disseminationRNA virus - mutations recombinationsCauses different diseasesMany different serotypes
5Ciliostasis TestTool to measure the effect of a virus on the tracheal mucosaThe tracheal mucosa represents a mechanic barrieragainst foreign particles in the respiratory tract(muco-ciliar apparatus)Consists of motile structures (cilia) and secretory cells(Goblet cells). They trap and eliminate foreign particles(ex. dust and bacteria).Tracheal rings of vaccinated and/or challenged birds areprepared and observed under the microscope.
8Ciliostasis test 10 tracheal rings 3 x top 4 x middle 3 x bottom Results 0 = 100% cilia moving1 = 75% cilia moving2 = 50% cilia moving3 = 25% cilia moving4 = 100% cilia moving
9Antigenic variation New serotypes of IBV can emerge as a result of few aminoacid changes in the S1 part of the spike genome of the virus
10Model of the structure of the “S” protein on the surface of the virus Virion membrane(Cavanagh, 1983)
11Cross protectionCross protection against IB viruses belonging to other serotypes may be due to the fact that most of the virus genome remains unchangedFrom a practical point of view it is thereforemore relevant to think in terms ofprotectotypes rather than serotypesThere are occasions when existing IB vaccinesdo not provide adequate protection againstnewly emerging serotypesWith the continual emergence of new serotypes of IBV it seems prudent to evaluate the level of cross protection obtained by the use of currently available vaccines.
13Experimental design 4 groups (10 SPF birds) 1 Massachusetts (Ma5) at 1 day2 4/91 at 14 days3 Massachusetts (Ma5) at 1 day & 4/91 at 14 days4 Not vaccinatedReared in isolators
14Challenge Challenged with different field isolates 5 weeks of age by eye drop (0.1 ml)Challenge dose: log CD50Ciliostasis test 5 to 7 days p. challengein all experiments, groups vaccinated andchallenged with homologous virus were included
15Example of results Maximum index = 40 Vaccine A: - No protection Ciliostasis IndexMaximum index = 40Vaccine A:- No protectionVaccine B:- Good protection
16Protection against: Arkansas Average ciliostasis indexVaccines used
17Protection against: Brazil Average ciliostasis indexVaccines used
18Protection against: Honduras Average ciliostasis indexVaccines used
19Protection against: South Africa (890/80) Average ciliostasis indexVaccines used
20Protection against: Taiwan (A1121) Average ciliostasis indexVaccines used
21Protection against: Holland (D274) Average ciliostasis indexVaccines used
22Protection against: Holland (D1466) Average ciliostasis indexVaccines used
23ConclusionsThe increasing prevalence of new serotypes creates difficulties in the design of adequate vaccination programs against IBIt is undesirable and not always necessary to consider developing new live vaccines for each new serotype
24ConclusionsThe concept of protectotypes is more relevant from a practical point of viewThe use of IB vaccines belonging to different serotypes may broaden the protection against a wide variety of antigenically different IBV’s