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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - DELTA-FLU (Dynamics of avian influenza in a changing world)

Teaser

Summary

Avian influenza is a major impediment to healthy and profitable poultry production in Europe and other parts of the world. The dynamics of avian influenza virus (AIV) infection in poultry populations have changed dramatically in recent years, resulting in major mortality of birds and significant economic losses. A striking example is the 2014-2015 emergence of highly pathogenic avian influenza virus of the subtype H5N8, which spread not only from South-East Asia to Europe, but also to North America, causing outbreaks in poultry holdings of seven countries with a loss of over 50 million heads of poultry. The subsequent introduction of H5N8 viruses in 2016/2017 was the source of numerous outbreaks in poultry farms in many European countries and underlines the importance of this virus type for farming but also wild life. And the recent detections of the related H5N6 virus demonstrates the continuous risks. In addition to the risk for poultry holdings worldwide, the potential for animal influenza viruses to become pandemic in humans is of great concern to public health. This occurred most recently in 2009, when a reassortant H1N1 influenza virus with gene segments from human, pig, and avian viruses caused the first influenza pandemic of the 21st century.
The overall objective of DELTA-FLU is to determine the key viral, host-related, and environmental factors that determine the dynamics of avian influenza in poultry and other host species, with the goal of improving prevention and control strategies against this important disease.
The overall objectives are:
1. Potential for certain HPAIV to be maintained in wild waterfowl populations and to spread long-distance along interconnected migratory flyways;
2. Key viral, host-related and environmental factors, both at regional and local levels, for incursion of AIV from wild birds into poultry holdings;
3. Roles of viral, host-related and environmental factors in the transition of LPAIV to HPAIV in poultry;
4. Role of the innate and adaptive immunity for AIV and effect of flock immunity against AIV on early detection and genetic drift;
5. Viral genetic factors that allow reassortants of avian and mammalian influenza viruses to transmit efficiently among pigs.

Work performed

In order to meet the objectives in this reporting period, research focused on the key questions of DELTA-FLU. The tracking of different species of wild ducks by placing GSM-GPS loggers on those birds resulted in the recording and analysis of their migration pattern in spring to breeding grounds in the north(-east) (e.g. Siberia), and vice versa in autumn. Active surveillance was performed using sentinel ducks, different AIVs were isolated throughout the year, and the contacts with other species were determined, including especially those known to frequent poultry farms. A database on notifiable avian influenza virus outbreak data since 2005 was generated, a first collection of data about the ecology of the wild bird-poultry interface, and the experimental modelling of the biosecurity barriers around poultry holdings was performed. The exposure of free-range galliform poultry to HPAIV-infected wild birds in a low biosecurity setting was further studied. In addition, a number of relevant AIV strains were collected by the project partners, and sequences of more than 250 avian influenza virus isolates were uploaded to publicly accessible databases. Experimental infections of European and North American wild duck and goose species, as well as several poultry species, were performed in order to determine levels of virulence and patterns of excretion. Furthermore, the development of a highly pathogenic AIV from a low pathogenic ancestor virus could be studied. Finally, the impact of the genetic make-up of a host was investigated focusing on the innate immune response of chicken lines to resolve the previously described differential susceptibility to influenza infection.

Final results

The collection and analysis of migration data will contribute to an improved understanding of connectivity between Asia and Europe via migratory birds as a potential portal of AIV incursion, which has a high impact on all future risk analyses and will allow new insights into AIV ecology. Furthermore, the results will form a basis for more targeted temporal and geographical surveillance of AIV in migratory waterfowl and identification and strengthening of weak spots in biosecurity around poultry holdings. The data will also allow a more precise prediction of introduction events e.g. due to bird migration.
The database on notifiable AIV outbreak data since 2005, the collection of data about the ecology of the wild bird-poultry interface, and the experimental modelling of the biosecurity barriers around poultry holdings elucidating possibly unrecognized routes by which AIV can cross the biosecurity barriers around poultry holdings, as well as variations among AIV strains in stability on fomites and ability to switch from anseriform to galliform hosts.
Understanding the underlying innate immune characteristics of poultry and the results obtained in AIV infection experiments will elucidate the relative importance of different components of the innate immune system against AIV infections, and the impact of the pre-infection adaptive immune status of poultry on the early detection and evolution of AIV. This will provide the necessary knowledge for future risk assessments and control strategies. This is of high importance since both the number of AIV introductions into Europe and the number of connected outbreaks in wild birds and poultry are as high as never before. The socio-economic impact of our data is therefore much higher as also the impact of AIV has so much increased within the last few years. Beside the commercial poultry farming it has also a considerable influence on the private breed of poultry and also the wild bird area, especially as far as protected species are concerned. It is therefore directly influencing and helping the commercial and the private sector and people who are engaged in those areas. The knowledge can then also be used by international organizations such as the FAO, OIE, EFSA or ECDC and the measures that have now been developed can also be taken into consideration in national and EU legislation. Finally, private industry working in the poultry field might implement measures developed here within the consortium to improve the biosecurity measures and lower the introduction rates.
Our studies will also reveal the true relevance of specific genetic changes in avian influenza viruses for the capacity to replicate and spread to different cell types of the swine respiratory tract and how this correlates with pathogenicity. Together with data from the ferret model, the zoonotic risk can be better assessed and there is an improved understanding of human spill over infections or the development of influenza virus strains with pandemic potential.
Finally, the establishment of ex vivo explants from chicken and ducks and of the porcine respiratory tract explant system is an effective way of representing the in vivo conditions and of reducing the number of animals used in experiments. This is of high impact for animal welfare ethics and is very much in compliance with the 3R principles.