Page 70 - Poultry-Punch April 2020 edition
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POULTRY PUNCH                                                                          ARTICLE






























                                                                  Nucleotide
                                                                  sequencing


                                                                 Discrimination
                                                             between vaccinal and
                                                                  field strains


            Diagnosis                                            l At what age protection against Infectious Bronchitis (IB) is most
              Virus neutralisation,  HI or ELISA  test  for measuring antibody   needed.
            are  helpful.    Virus  isolation  in  embryos  or  chicken  kidney  cell  l The  field  viruses  present  will  determine  which  vaccines

            cultures  and/  or  PCR  are  necessary  for  a  definitive  diagnosis.   (protectotype) to choose.

            Curling, stunting and death of embryos can be seen in inoculated  l Interference with other (live) vaccinations must be avoided (IB
            embryonating  eggs.  Respiratory  signs  and  lesions  with  kidney   vaccine viruses can interfere with for example Newcastle disease
            lesions give a presumptive diagnosis.               vaccine viruses).
              Tracheal swabs or fresh samples of trachea are most useful for   Layers and breeders  –  The  aim  of  vaccination  is  to  protect
            virus detection or isolation. Direct immunofluorescence staining  the  oviduct  as  IB  infections  may  result  in  false  layers,  drops  in
            of tracheal tissue smears is useful in the diagnosis of early cases  production and changes in the internal and external quality of the
            before secondary bacterial infection has occurred.   eggs.
                                                                 l In  this  context  vaccination  of  young  chickens  is  often  done
            Virus Isolation-genome detection                    at an early age (first day(s) of life), and especially in broilers
               l RT–PCR – is used with specific primers to detect the genome of   focusing  on  inducing  enough  protection  so  as  to  cover  the
              the virus in tracheal samples or inoculated embryonated eggs or   whole fattening period. In layers and breeders the programs
              tracheal organ cultures.                          are focused in protecting the oviduct during the first weeks of
               l RFLP, – which recognizes the genome of the IBV and is used to   life with modified live attenuated vaccines. Later on during the
              determine the genotype.                           production period immunity needs to be broad and long lasting,
               l IBV typing by nucleic acid sequencing.         and inactivated vaccines are often used.
               l IBV typing by real–time RT–PCR.                Broilers  –  Vaccination  is  focused  on  reducing  the  economic
                                                              losses caused by IB infections as these are reflected in weight loss
            Vaccination programs for Infectious               and general poor performance of the flock.
            Bronchitis (IB) vaccines                            In general milder live vaccines (Ma5) can be used from 1 day
              No  general  vaccination  rule  can  be  applied.  Each  vaccination  of age onwards. A period of 2 weeks should be left between the
            program must be adapted to the demands of the field situation.  applications of 2 live vaccines. The inactivated vaccine is usually
              Some  considerations  have  to  be  taken  into  account  when  used at around 16 to 20 weeks of age. A period of 4–6 weeks should
            applying IB vaccines:                             be left between the last live IB vaccine and the inactivated vaccine..



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