7/7/2021:  Gumboro disease is caused by (vv)IBDV (very virulent infectious bursal disease virus). In the Netherlands, we have seen genetic mutations in the vvIBDV DV86 strain since 2014.

In the monitoring, GD has detected this mutated vvIBDV strain, which is 98.1 percent compliant with the ‘classic’ DV86 strain, at dozens of farms throughout the country (broilers and young layers) since 2017. The most commonly detected issues were excessive losses, wet barns, reduced growth and reduced technical results. If the mutant field strains are quicker to break through the maternal antibodies than the ‘old’ field strains, there is a greater risk of early field infections. This may result in suppression of the poultry immune system, which will have consequences for the vaccine strains and vaccination schedule to be applied. In 2020, GD researched the ‘classic’ vvIBDV DV86 strain and the new strain in order to determine the capability of each strain to break through the maternal immunity, triggered by vaccination of the maternal animals. The cut-off titre exceeded 1000 in both the classic DV86 strain and the 98.1 percent DV86 strain, which is more than twice that of the ‘hot’ vaccine strains. This knowledge enables us to hone vaccination timing, to make vaccination choices and to more effectively estimate the risk of early infection.