At the National Reference Laboratory for Avian Influenza, samples (organs, swabs, carcasses) are examined for direct virus detection by real-time RT-PCR, sequencing and with egg culture and haemagglutination test (HA). The indirect detection by determination of antibodies is done by ELISA and haemagglutination inhibition test.
Haemagglutination test: Certain viruses such as influenza viruses bind erythrocytes to their surface via haemagglutinin. This causes the blood to clump together (agglutination). The amount of virus can be determined by dilution series.
Haemagglutination inhibition test: Specific antibodies can prevent agglutination/clumping caused by the virus. In this way antibody titres and individual virus strains can be determined.
ELISA: Enzyme-linked Immunosorbent Assay is an antibody-based detection method, antibodies bind to an antigen and are detected by an enzymatic colour reaction.
Real-Time RT-Polymerase-Chain-Reaction (PCR) and sequencing: AI virus gene sequences are detected and H5 or H7 types can be distinguished directly. The pathotype of the virus strain (high or low pathogenic) can be determined by sequencing.
Egg culture: A potentially infectious vaccination solution is prepared from the samples, which is used to inoculate virus-free chicken eggs. These eggs are incubated for at least five days. If highly pathogenic avian influenza viruses are present, the embryos in the eggs die and the virus in the allantios can be identified by haemagglutination (HA).