A field study on the significance of vaccination against infectious bursal disease virus (IBDV) at the optimal time point in broiler flocks positive for maternally derived IBDV antibodies

• Published in: Avian pathology 2008-06, Vol.36 (5), p.401-409
• Main Authors: Block, Hermann, Meyer Block, Karen, Rebeski, Dierk E., Scharr, Heike, de Wit, Sjaak, Rohn, Karl, Rautenschlein, Silke
• Format: Article
• Language: English
• ISSN: 0307-9457; 1465-3338
• DOI: 10.1080/03079450701589175

The right strategy for infectious bursal disease (IBD) control and its success rate under field conditions depends on hygiene management, IBD-field pressure, level and variation in maternally derived IBD antibody (MDA) levels, and the IBD-vaccine strains to be used. Usually, standard vaccination programmes are used, which are not always adapted to the specific conditions on the farm and the chickens. Employing the ‘Deventer formula' may help to estimate the optimal time point for vaccination for a specific flock based on the MDA level, its variation, the genetic background of the chicken, and the IBD-vaccine strain. Two field studies with 16 or 20 commercial broiler flocks were conducted applying an intermediate IBD-vaccine before, at the best, and after the estimated optimal vaccination time estimated by the ‘Deventer formula'. These studies showed that flocks, which had been IBD-vaccinated between one day before, at, or up to three days after the estimated optimal time point, developed detectable humoral immunity up to 14 days post vaccination. If birds had been vaccinated more than one day before the calculated optimal vaccination date, the humoral immune response was delayed or non-detectable until slaughter. The induction of humoral immunity correlated with the incidence of bursa lesions and IBDV-detection by RT-PCR. As indicated in this study, under field conditions bursa lesions may develop later than predicted based on experimental experiences. The late incidence of bursa lesions after vaccination may be confused with field virus-induced lesions, in which case sequencing may offer a valuable tool for differentiation.