Division 1 Directive 2005/94/EC and the diagnostic manual

Sections 2 and 3 of Chapter IX, of Directive 2005/94/EC allow the use of emergency and preventive vaccination under certain conditions. One of those conditions is that a ‘DIVA’ (Differentiating Infected from Vaccinated Animals) strategy is employed.

Vaccination must be aimed at preventing the infection and subsequent spreading of virus between flocks. There is indisputable evidence to show vaccination increases the amount of virus needed to infect birds and decreases the amount of virus excreted. However, although vaccinated birds do no longer develop clinical signs they can still spread virus when challenged. Thus HPAI viruses of H5 and H7 subtypes could circulate unnoticed for some time in a flock with suboptimal levels of immunity in the same way that LPAI viruses could do in an unvaccinated flock. There is therefore a need to be able to identify virus positive vaccinated flocks that have become infected with field virus so that other control measures, such as stamping out, can be implemented.