Information of the FLI on the current AI Situation
Aquatic wild birds represent the main reservoir for all naturally occurring influenza A virus subtypes (avian influenza, AIV: presently 16 H and 9 N subtypes). Within this host pool, AI viruses usually perpetuate without any significant consequences for their hosts. If there is possibility for exposure and host and virus have the necessary disposition, virus transmission from this reservoir to poultry and mammals – including humans – is possible.
In domestic poultry, AI viruses of the subtypes H5 and H7 can mutate spontaneously into highly pathogenic forms (highly pathogenic avian influenza viruses, HPAIV), which are the actual causative agents of classical fowl plague. Especially in chicken and turkey holdings, classical fowl plague causes massive losses and is therefore of high economic relevance. If humans are exposed to high infectious doses of HPAIV, but also some AIV which are low pathogenic in poultry (LPAIV), the virus can be transmitted and cause fatal disease in humans. This applies for example to HPAIV of the subtype H5N1 and the LPAIV H7N9 detected in China.
Prevention and control of classical fowl plague are regulated by national legislation. The emphasis is laid on biosafety measures to prevent an introduction of the pathogens into poultry holdings and their spread in the poultry population. Early detection of possible infections in poultry is of utmost importance; infectiological diagnostics play a decisive role. This concept also includes extensive monitoring of wild birds and poultry.
The NRL for AIV is the direct contact and reference center for federal and state authorities, especially for questions relating to diagnostics, and is also active within the European network of national reference laboratories. As reference laboratory of the World Organisation for Animal Health (O.I.E.) and of the Food and Agriculture Organization (FAO) of the United Nations the laboratory also provides advice and diagnostic assistance to countries outside Europe. The laboratory conducts application-oriented research in the field of AIV diagnostics, epidemiology and pathogenesis. Furthermore, the NRL deals with scientific questions relating to porcine influenza.
- Virus, antigen and genome detection in test materials from poultry, wild birds and pigs
- 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 haemagglutinin cleavage site
- Identification of Influenza A viruses of the subtypes H5 and H7
- Determination of the haemagglutinin and neuraminidase subtype of influenza A isolates
- Investigation of poultry and wild bird sera for antibodies against influenza viruses especially of the subtypes H5 and H7
Assistance and surveillance
- Coordination of the diagnostic procedures applied by the regional laboratories
- Asservation of virus isolates from confirmed cases of disease and transfer of selected isolates to the EU reference laboratory
- Collection and preservation of reference virus strains, antigens and antisera
- Participation in EU ring trials
- Organization of national interlaboratory ring trials
- Direct contact for federal and state authorities for questions regarding AI diagnostics and control
- Advisory function for O.I.E., FAO and WHO concerning avian influenza virus infections
- O.I.E. Twinning laboratory for Egyptian national AI reference laboratory
The standard diagnostic procedures applied by the NRL for AI are listed in the valid „Arbeitsanleitungen zur Diagnose anzeigepflichtiger Tierseuchen“ (Manual for diagnostics of notifiable animal diseases) published by the BMELV (Federal Ministry for Food, Agriculture and Consumer Protection). In detail, the following methods are used:
- Virus isolation from embryonated chicken eggs
- Genome detection by PCR
- Determination of the haemagglutinin subtype by means of haemagglutination inhibition (HI) test, PCR/sequencing and DNA chip
- Determination of the pathogenicity by sequencing of the haemagglutinin cleavage site and/or determination of the intravenous pathogenicity index (IVPI)
- Determination of the neuraminidase subtype by means of PCR, DNA chip and neuraminidase inhibition test
- Detection of antibodies against influenza viruses by means of ELISA
- Detection of antibodies against AIV subtypes H1 to H6 by means of HI test and subtyping of antibodies
- Detection of neuralizing antibodies against influenza viruses
- Characterization of Egyptian HPAIV H5N1 and H9N2 (supported by DAAD; PhD student M. Naguib)
- Europe-wide monitoring of porcine influenza viruses (supported by IDT Biologika; PhD student D. Henritzi)
- Investigations on spontaneous mutations of low pathogenic AIV of the subtype H7 (intramural support; PhD student A. Graaf)
- Risk of introduction and spread of high pathogenic AIV into European poultry holdings (EFSA work group)