Aquatic wild birds are the main reservoir of all influenza A virus subtypes occurring naturally in birds (avian influenza, AIV: currently 17 H (1-16, 19) and 9 N subtypes). In this host pool, AI viruses usually circulate without major clinical effects on their hosts. Spontaneous and accidental transmission of viruses from this reservoir to poultry and also to mammals - including humans - is (rarely) possible.
AI viruses of subtypes H5 and H7 can mutate spontaneously in poultry into a highly pathogenic form (highly pathogenic avian influenza viruses, HPAIV), which causes severel diseases in birds. This disease pattern of “highly pathogenic avian influenza” (HPAI) occurs particularly in chicken and turkey flocks with very high loss rates and is therefore of great economic importance worldwide. HPAIV, but also some low pathogenic avian influenza viruses (LPAIV), can also be transmitted to humans when exposed to a high infectious dose and can also cause fatal diseases in humans. Examples of this are the HPAIV subtypes H5N1 and H5N6 as well as the LPAIV H7N9, which has only been detected in China.
Prevention and control of HPAI are regulated by EU regulations throughout Germany. The main focus here is on biosecurity measures to protect against the pathogens entering poultry farms and to prevent their spread in the poultry population. The early detection of possible infections in poultry is of crucial importance; infectiological diagnostics makes a significant contribution to this. Extensive monitoring tests in wild birds and poultry are also integrated into this concept. Since 2023, HPAIV vaccination of poultry can also be used as an additional preventive measure in the EU, although this is linked to extensive monitoring of vaccinated flocks. If, despite all preventive measures, an HPAIV infection is detected in a poultry flock, containment measures in the form of a flock closure, the killing of all poultry present and their destruction will take effect.
The National Reference Laboratory for Avian Influenza (NRL-AI) acts as a direct contact and reference center for federal and state authorities, especially in matters of diagnostics and vaccine-mediated prevention. The NRL-AI is also active in the European network of National Reference Laboratories. As a reference laboratory of the World Health Organization for Animals (WOAH) and the Food and Agriculture Organization (FAO) of the United Nations, the laboratory is also available to non-European countries for advice, diagnostic assistance and training. The laboratory conducts applied research in the field of diagnostics, epidemiology, pathogenesis and prevention of influenza infections in birds and pigs.
Diagnostics
- Infectivity, antigen and genome detection in test materials from poultry, wild birds and pigs as well as in environmental samples
- Identification of avian and porcine influenza virus isolates
- Characterization of the pathogenicity of avian virus isolates by determination of the intravenous pathogenicity index and/or sequencing of the cleavage site of the haemagglutinin
- Identification of influenza A viruses of subtypes H5 and H7
- Determination of the haemagglutinin and neuraminidase subtype of influenza A isolates
- Testing of poultry and wild bird sera for antibodies against influenza A virus, in particular subtypes H5 and H7
Supervision and monitoring
- Coordination of the diagnostic procedures used in the regional testing offices
- Investigations and assessments as part of approval procedures for commercial diagnostic kits (see also approval office: LINK)
- Preservation of virus isolates from confirmed cases and transfer of selected samples, isolates and nucleotide sequences to the EU reference laboratory
- Production, collection and preservation of reference virus strains, antigens and antisera
- Participation in international ring tests
- Carrying out national comparative laboratory tests (ring test)
Consulting
- Direct contact for federal and state authorities on AI diagnostics and control issues
- Advisory activities for WOAH, FAO and WHO regarding avian and porcine influenza virus infections
Research
The NRL-AI is a partner in various working groups and research projects in collaboration with national and European partners. The research work focuses on the further development and standardization of AI diagnostics as well as on questions of pathogenesis or immunization and the occurrence of influenza viruses in wild birds. Research studies are also being conducted on the spread and significance of influenza infections in domestic pigs.
The following projects have recently been successfully completed:
- Characterization of avian influenza viruses from Iranian wild bird samples (funded by DAAD; PhD student A. Modiri, University of Tehran, Iran) Monitoring of porcine influenza viruses in large flocks of domestic pigs in Germany with transition of influenza viruses between humans and pigs (Dr. C. Henning, funded by the DFG) Use of live influenza virus vaccines in pig farming (PostDoc, Dr. A. Graaf-Rau) in the framework of the EU-ICRAD project “PIGIE”)
Current projects:
- HP H5 infections with zoonotic component in wild birds and mammals (Dr. A. Günther, partner in the EU Horizon project “Kappaflu”)
- Vaccination options against HPAI in goose farming in Germany (in cooperation with the NRL-ND, PD Dr. Grund, Ms. R. Piesche; funded by the animal disease funds of the federal states)
Projects from 2025:
- Mass-applicable influenza A virus vaccines for use in poultry and pigs (Ms Dr. S. Chepkwony, Kenya; funded by a Georg Forster grant of the Alexander-von-Humboldt foundation).
The standard diagnostic methods used in the NRL for AI are listed in the current “Arbeitsanleitungen zur Diagnose anzeigepflichtiger Tierseuchen” (publisher: BMELV). The following methods are used in detail:
- Virus isolation in incubated chicken eggs and in cell cultures
- Genome detection using real time RT-PCR
- Determination of the haemagglutinin subtype using the haemagglutination inhibition test (HAH), PCR and sequencing (Sanger or NGS)
- Pathogenicity determination by sequencing the cleavage site of the hemagglutinin and/or determination of the intravenous pathogenicity index (IVPI)
- Determination of the neuraminidase subtype by PCR
- Detection of antibodies against influenza viruses using ELISA
- Detection of antibodies against AIV subtypes H1 to H16 using HAH and subtype-specific ELISAs
- Detection of neutralizing antibodies against influenza viruses
- Characterization of avian influenza viruses in Iranian wild bird samples (funded by DAAD, PhD student A. Modiri, University of Teheran, Iran)
- Monitoring of swine influenza viruses in large pig holdings in Germany (DFG project in co-operation with Prof. Dr. M. Schwemmle, University of Freiburg, Germany; PhD student N.N.)
- Efficacy of live attenuated vaccines against swine influenza viruses (funded by CEVA Animal Health; PostDoc Dr. Annika Graaf-Rau)
- Transmission of influenza viruses between humans and pigs (PhD student Christin Hennig)
Last updated November 29, 2022