At the end of the 20th century, a highly pathogenic (HP) H5N1 avian influenza virus emerged. It was able to infect and spread worldwide via wild water birds. Many highly pathogenic H5 avian influenza viruses deriving from this source posed a direct threat to the poultry sector and, for some variants, even to humans. This project aims to better understand spread of a HP H5 variant inside a flock, after punctual introduction. In addition, tools will be developed to facilitate and optimise expertise of the national reference laboratory (NRL).
At the end of the 20th century, a highly pathogenic H5 virus emerged and infected wild water birds. As a consequence, the highly pathogenic virus could contaminate directly poultry flocks without the need for adaptation from low to high pathogenicity. The wild migration of birds infected by the HP H5 viruses resulted in a global spread of these viruses. Since its emergence, the H5N1 goose/Guangdong parent strain evolved, by genetic drift and shift, into a large number of different clades and subclades, with varying pathogenicity and host-spectrum.
Since 2010, different subtypes of the clade 188.8.131.52 viruses appeared, such as H5N2, H5N3, H5N6 and H5N8 strains that share the same hemagglutinin (H) but differ by their Neuraminidase (N) as a result of re-assortment with locally circulating avian influenza viruses. These strains gradually spread from Asia towards Europe, Africa (H5N1, H5N6 and H5N8) and even North America (H5N1, H5N2 and H5N8). Belgium has been confronted with two waves of introductions of the clade 184.108.40.206.b virus in 2017, mainly in wild and hobby birds.
As a response to the possibility of a direct introduction of highly pathogenic avian influenza viruses into poultry flocks via wild birds — instead of emergence by genetic drift of a LPAI-H5 virus — combined with the changing pathogenicity and epidemiology, a better monitoring and protection of our poultry flocks is needed.
Firstly, a better understanding of HP H5 spread inside a poultry flock after direct punctual HP H5 introduction is essential to improve scientific knowledge and the current monitoring and control approaches for HP H5 viruses. In this context, this project aims to develop an experimental model of punctual introduction of HPH5Nx into naïve and pre-immunised poultry flocks of different species. By doing so, we will be able to study the possible silent circulation inside flocks with pre-existing immunity due to endemic situations or vaccination.
In addition, the impact on egg production and egg infection will be evaluated. Tools will be developed in order to identify recent infections, enabling to dicriminate Low Pathogenic (LP) from High Pathogenic H5 pathotypes, and to facilitate in field virological sampling. All of the above should allow the national reference laboratory to easily adapt to changing epidemiological situations, to extend its expertise and to support the authorities in charge of protecting the poultry sector.