SCHWARZER K., Awaad M.H.H. Abdel-Alim. G., Susan El Mahdy, Arnouts S.

Modulating the Immunosuppressive Effect Associated with Infectious Bursal Disease Virus Infection or Vaccination in layer Chickens

Poultry is often challenged by Immune suppression causing immune deficiency. Infectious bursal disease virus infection (IBDV) causes severe immuno-suppression of chickens (Saif et al 2003). Infection with IBDV at an early age significantly compromises the humoral and local immune response of chickens.

This study has been conducted in an attempt to modulate the immunosuppressive effect associated with infection with virulent IBDV (Phase I); or vaccination with intermediate plus IBDV strain 228E vaccine (Phase II) in layer chickens by using immuno-stimulants; Immunoaid dry (mannanoligosaccharides and fermentation extracts of Saccharomyces cerevisiae) and Nutrilac I.G.A. (lactic, formic acid and fermentation extracts). For estimation of the immune response, all groups were vaccinated with Newcastle disease virus (NDV) vaccines and bioassay study was carried out by NDV challenge.

The bioassay studies using vvNDV challenge proved the potency of NDV strain where infection resulted in 100% mortality in ND unvaccinated immune-compromised, untreated chickens group (control). Moreover the efficacy of the used NDV vaccines was well documented as the protection percentage reached 97,2% and 100% in blank vaccinated control groups.

The results of phase I and II indicated that the two used immuno-stimulants partially compensated the humoral immune suppression when used either before (prophylaxis) or after (therapy) IBDV infection or vaccination.

The prophylactic study showed a relatively higher protection percentage against vvNDV challenge in Immunoaid dry (86,5%) and Nutrilac I.G.A. (83,8%) treated groups than their untreated control (78,4%). The therapeutic use of these preparations revealed that Immunoaid dry improved the protection percentage in immuno-compromised birds by field IBDV infection (83,8%) while Nutrilac I.G.A. gave the best results (95%) in immuno-compromised chickens by IBDV vaccination.

The Bursa Fabricious of all the groups were examined at day 7 and day 14 post infection or vaccination. Different degrees of regeneration in their damaged lymphoid follicles were observed at 14 days, which confirm the compensatory effect of the studied immuno-stimulants. Nutrilac I.G.A. relatively gave the best regeneration score.

The present findings indicate that the used immuno-stimulators compensate immuno-suppression caused by IBDV infection or vaccination.

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