build-up of more virus pressure be prevented, cycle after cy- cle. A live vaccine will stop the evolution of the IBD virus to- wards a form that could escape the prevention programme. In addition to vaccination, other factors that need to be ob- served for optimum short and long term control of Gumboro disease include biosecurity, cleaning and disinfection, as well as passive immunity.
Improve performance The immune-complex vaccines, like Transmune, are prepared from live attenuated IBDV strains of the intermediate plus type, mixed in with specific anti-IBDV serum to regulate the safety and release of the vaccine once the MDA levels of the chicken have been reduced. These vaccines have the ability to fully colonise the bursa, protect against all field IBD viruses and overcome MDA; some of the key advantages of the im- mune-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 immunised against any type
of IBD virus. In this way the vaccine can control the Gumboro disease, whether clinical or subclinical, and ensure that the chickens are ‘protected’ against clinical signs following infec- tion. At the same time it helps to ‘prevent’ the disease by de- creasing the population of Gumboro virus shed and by significantly reducing the risk of a variant virus emerging. Experience from around the world covering all the conti- nents has shown that the Transmune concept which blocks the bursa with the vaccine strain works to control the dis- ease. Benefits have been seen in the field and on farm, and some can even be measured in the slaughterhouse as well. A well-protected healthy broiler flock will perform well and show good results, achieving its potential according to the genetic and nutritional strategy pursued. A more uniform flock therefore makes processing more efficient, while also making it possible to increase the line speed. To summarise: the significance of controlling Gumboro disease using Trans- mune vaccination is that it maintains the consistency of broiler production, protecting against clinical and sub-clini- cal infection, thus ensuring the uniformity of the results in the field and at processing.
▶ POULTRY WORLD | No. 4, 2021
Controlling Gumboro dis- ease on a con- sistent basis protects broilers against the clini- cal signs of the virus and pre- vents the risk of future challeng- es from the farm environment.
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