Field and laboratory findings following the large-scale use of intermediate type infectious bursal disease vaccines in Denmark
Following a period of clinical outbreaks of very virulent infectious bursal disease virus (vvIBDV) in Denmark, the histological bursal lesion score (HBLS) was used on a national scale to screen broiler flocks vaccinated with intermediate IBD vaccines for lesions indicative of IBDV challenge.
High lesion scores were detected in a high percentage of healthy and well performing flocks despite the lack of other indications of the presence of vvIBDV. RT–PCR and subsequent sequencing showed the frequent presence of H253Q and H253N IBDV strains that were genetically close to the
sequence of the intermediate vaccines with a relative risk ratio of 13.0 (P < 0.0001) in intermediate vaccine A or B vaccinated flocks compared to unvaccinated flocks. The relevance of these H253Q and H253N strains was tested under experimental conditions using a protocol
derived from the European Pharmacopoeia for safety of live IBD vaccines. The results confirmed the higher pathogenicity for the bursa of these strains compared to intermediate vaccines as well as the negative effect on antibody response to a Newcastle disease (ND) vaccination performed at
the peak of the bursa damage. The efficacy of the ND vaccination was still 100% showing that the H253N and H253Q IBDV strains would be considered as safe vaccine viruses. In conclusion, the use of the HBLS to screen commercial broiler flocks vaccinated with intermediate IBD vaccines for the
presence of vvIBDV does not seem to be a reliable method due to the frequent occurrence of H253N and H253Q strains in those flocks. For screening of IBD vaccinated flocks for the presence of vvIBDV or other field strains, the RT–PCR with subsequent sequencing seems to be most suitable.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Article Media
Infectious bursal disease;
Document Type: Research Article
Landbrugets Veterinaere Konsulenttjeneste (LVK), Hobro, Denmark
GD Animal Health, Deventer, the Netherlands
MSD Animal Health, Boxmeer, the Netherlands
Elanco Animal Health, Utrecht, the Netherlands
Ceva Animal Health, Libourne, France
Veterinary Faculty, University of Utrecht, the Netherlands
Ceva Animal Health, Lenexa, KS, USA
Publication date: November 2, 2018
More about this publication?