Outbreak Investigation and Molecular Characterization of Infectious Bursal Disease Virus and Vaccine Immunogenesity Trial in Ethiopia
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Date
2015-06
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Addis Ababauniversity
Abstract
Infectious bursal disease (IBD) is a highly contagious and economically important
immunosuppressive viral disease of poultry that is found worldwide. The disease is caused by a
dsRNA virus. This study was conducted in National Veterinary Institute from September 2015 to
April 2015 on the objective of the isolation, identification and molecular characterization of
infectious bursal disease virus (IBDV) on infectious bursal disease (IBD) suspected outbreak
samples were collected from 2013 to 2015 from different parts in Ethiopia and to test the
immunogenicity of four different live attenuated commercially available infectious bursal disease
vaccines and also to select the appropriate infectious bursal disease virus vaccine through the
selected different IBDV vaccine immunogenicity test and cross protection test against the local
isolated VVIBDV challenge virus and also to determine the appropriate time of IBDV vaccine
administering time on vaccinated progeny originated chickens. A representative outbreak
samples were employed for virus isolation (cell culture) on chicken fibroblast cell (CFC),
molecular characterization (touchdown PCR) and PCR positive isolates subjected to further
sequencing. On the other hand the IBDV vaccine immunogenicity test was conducted by
employed the four different live attenuated commercially available infectious bursal disease
vaccines strain: Namely (one mild intermediate strain - D78, one invasive intermediate strain -
Bursine-B2k, and two intermediate plus or hot strain IBD LC75 and IBD EXTREM) and
infectious bursal disease virus maternal antibody (IBDV MAb) free specific pathogen free (SPF)
chickens of vaccinated progeny and also the recently local isolated very virulent infectious
bursal disease virus (VVIBDV) as a challenge virus. The IBDV MAb was screened the
experimental SPF chickens before administering the experimental IBDV vaccines. The chickens
sera was collected and examined post 14 days of primary immunization, post 7 days of booster
dose or prior to challenge test and also 21 days post challenge test serologically by flock IBDV
antibody screening ELISA kit to compute the immunogenicity and cross protection capacity
against the challenge locally isolated VVIBDV. Among the study objectives and criteria’s results
were revealed as followed, Eighteen (95%) of bursa and four (80%) of the spleen samples
suspensions were grown and develop visible cytopathic effect (CPE) on chicken fibroblast cell
cultures (CEF), totally nineteen cell culture isolates (eleven 2013 and 2014 samples and seven
2015 samples) were revealed the expected VP2 gene amplified PCR band (645base pairs); the
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eleven 2013 and 2014 positive PCR products sequence analysis were also confirmed the
currently circulated IBDV were VVIBDV virus. On the other hand based on those computed
parameters, the IBDV vaccine immunogenicity test studies were revealed that the IBDV vaccine
administration appropriate scheduled on vaccinated progeny flocks should be at 21 and 35 days
age for primary and booster dose vaccination respectively and also the superior immunogenic,
potent and efficiently cross protective for recently local isolated VVIBDV was intermediate plus
IBDV vaccine strain LC75. Therefore based on the above study results the following points were
recommended producing this candidate live intermediate plus IBDV vaccine strain LC75 should
be effective to prevent and control the currently circulated VVIBDV virus, commercial poultry
farm owners should be screened the IBDV maternal antibody (MAb) of the flock before primary
IBDV vaccine administration , and IBDV virus molecular epidemiology study with a planned
interval should be conducted to assessed the antigenic diversity of the IBDV virus.
Key words: Infectious Bursal Disease Virus (IBDV), IBD, IBDV vaccine, polymerase
chain reaction, sequencing, IBDV maternal antibody
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Keywords
Infectious Bursal Disease Virus, (IBDV, IBD, IBDV vaccine, polymeras, chain reaction, sequencing, IBDV maternal antibody