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Friday, April 28, 2017

Management of infectious bursal disease virus( IBDV) in broilers.

The management of infectious bursal disease virus( IBDV) in broilers for most farmer is to ensure a strict and vaccination regime for their breeders. The maternal immunity passed on to chicks will usually help protect them until they are 3 to 4 weeks of age. This projection of conferred immunity sometimes does not work out like planned due to certain factors; 1) Efficacy of some vaccines. 2) Vaccine failure or break. 3) Early infection of flock before 2 weeks of age leading to permanent immune suppression despite maternal immunity. When IBDV infection in broiler flocks occurs after 3 to 4 weeks of age , when maternal immunity has waned it can result in reduced feed efficiency, slowed growth rate and uneven size of flocks. This will also lead to temporary immune suppression with a higher risk of secondary infections, which often become more critical in antibiotic-free production. The prevention of the damaging effects of IBDV by farmers can be initiated by simulating active immunity in their flocks. Live, attenuated vaccines used in layers with high success rate can also help prevent IBDv in broilers. Farmers have turned to in-ovo vaccination at hatchery at day 1 to forestall any disease occurrence. The common vaccines are the recombinant herpesvirus of turkey HVT- IBDV and immune-complex (IC) vaccines. . The efficacy of HVT-IBDV vaccines has been demonstrated as these vaccines have been shown to induce protection against multiple IBDV strains with no risk of bursa damage. The key to effective use of HVT-IBDV is that it should be the only recombinant vaccine used in the flock to prevent interference. Combining recombinant HVT-IBDV vaccines with other recombinant HVT vaccines e.g for Newcastle disease or infectious laryngotracheitis is not recommended because viral interference can occur between the HVT viruses. In cases where an HVT recombinant vaccine is needed to manage either of the respiratory diseases, an alternative to the HVT-IBDV vaccine is recommended. The immune-complex vaccines (IC) contain a mixture of modified-live vaccine virus and anti-IBDV antibody. The antibodies in these products bind to the IBDV vaccine virus. These antibodies greatly reduces the ability of the vaccine virus to replicate early in the broiler’s life ,thus damage to the bursa and immune suppression are minimal and often undetected. This ability to act early in the of the broiler makes the IC-IBDV vaccines a safe alternatives to HVT-IBDV vaccines. Vaccinating with an IC-IBDV vaccine in the presence of maternal antibodies to IBDV seems counter intuitive or counter-productive but these vaccines have been shown to stimulate active immunity to IBDV, even when maternal antibody titers are relatively high.

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