23 April 2024

3 minute read

By: Marco Aurélio Elmer Lopes, DVM

In the last parts of a series of 6 articles was discussed the impact of the Gumboro Disease in the poultry production, and how the control starts from the breeders vaccination.

Let´s remind the key approaches that should be considered:

• Vaccination of the breeders, to transfer Maternal Antibodies to the chicks
• Vaccination of the broilers
• Biosecurity
• Diagnostic and surveillance
• Environment management

Broilers Vaccination

As already described, the MDAs (Maternal delivered antibodies) will be essential for the early-life protection. But after the decrease of the MDA level the chick should build their own active immunity.

As the commercial poultry production demands a high performance from the broilers, it is key a proper control of Gumboro disease (IBD).

And not just protect the disease outbreaks, but fundamentally prevent the risk of replication of the field strains, what is named prevention, as it is known, its can impact the results in the field and the processing of the broiler's carcass in the slaughterhouse.

For that the name of the game on the controlling for IBD will be though vaccination block the bursa, by the replication of the vaccine virus, and this way preventing the field strains from infecting the chick.

The objectives of Gumboro vaccination program must be:

For this, a live virus must be used, so that this block actually occurs. The strain used in the immune-complex IBD vaccine, as the W2512, must be attenuated and maintain its invasiveness without generating any kind of permanent damage to the cells of the bursa. It is important to note that the lymphoid depletion generated by intermediate or intermediate plus strains, in which a decrease in bursa size is observed, is physiological and transient, not impacting the immune system of birds.

At the same time, this virus must be protected by antibodies (Virus Protecting Immunoglobulins VPI) so that the release occurs at the right time, and the inactivation of this vaccine virus does not occur, as in the Immune-complex IBD vaccines. A correct balance between the IBD virus and the anti IBDV antibodies is of crucial importance for the efficacy and safety of these vaccines.

The immune-complex vaccine, as Transmune®, have the ability to fully colonize the bursa, protect against all field IBD viruses and overcome MDA; some of the key advantages of the immune-complex vaccines. The vaccine take occurs when the MDA level decreases to a point that allows the vaccine virus to be released and to reach the bursa of Fabricius. From this moment on, the vaccine strain will replicate in the bursa of Fabricius and the chicken will be immunized against any type of IBD virus.

The fact that the virus is covered by VPI´s is important to maintain safety and stability in chickens with varying levels of maternal antibodies. In case of low levels of MDAs, replication of the vaccine virus will occur earlier, and in birds with higher levels of MDA, it will occur later. In all birds thus adapted according to the most appropriate time for replication, and thus onset of active immunity.

GUMBORO DISEASE CONTROL

Understanding the important to block the bursa by a live vaccine, and in this way prevent the build-up of a higher virus pressure, cycle after cycle, and stop the evolution of the IBD virus towards a form that could escape the prevention program.

These are the consequences of the ‘protection against shedding’. In other words, the objectives of a sound Gumboro vaccination program should aim at stopping the Gumboro cycle. To achieve the stop of the Gumboro disease, the vaccination program should be well fitted.

Conclusion

As summary, to have IBD control and keep the consistency of the broiler production, provide protection against clinical and sub-clinical infection, and prevention of field virus replication is essential. But it should be done with safety, as the immune-complex vaccine Transmune®, that adapts to different maternal delivered antibodies levels, blocking the bursa for a better Gumboro disease control.