4/12/2024: 

It is remarkable that virtually no antibodies against low-pathogenic avian influenza (LPAI) viruses were detected in commercial poultry during the outbreak of highly pathogenic AI (HPAI) H5N1 in 2022 and the first three quarters of 2023.

Antibodies against LPAI

The most recent AI-positive serum samples dated from March 2022 (antibodies against LPAI-H6N8). It wasn’t until the end of November 2023, that antibodies against low-pathogenic avian influenza were detected again using the AI ELISA. So far, antibodies have been detected in a broiler flock (against H3N3) and at six laying farms (against H9Nx, H5N4, H7N3, H6N2 and H5N1) spread across the country. At the time of writing, further analyses are being carried out for two additional farms housing laying hens; all that is known to date is that the positive ELISA results have not been caused by H5 or H7. Decreases in production and/or feed intake were noted in several of the laying flocks before the blood sampling moment, though it has not been demonstrated that these observations were caused by the LPAI infection.

LPAI virus detected

A team of specialists led by the Food and Consumer Products Safety Authority (NVWA) visited three laying farms, based on the positive serology for H5 or H7 antibodies. At the end of November, the LPAI-H7N3 virus was detected by PCR in addition to the positive serology at one farm with minor production problems. This subtype was also detected in Scotland in 2023, and in the United States in preceding years. The farm’s flock was not culled but the NVWA did block it while the virus was present, a period that lasted several weeks. For the other farm that had positive serology at the end of the production period, PCR showed the
LPAI-H5N4 virus to be present. This subtype is new in the Netherlands (for commercial poultry). It has however previously been detected in waterfowl and seagulls in Germany, with the virus being composed of genes found in different AI viruses in Europe and Asia. At the third farm, the LPAI-H5N1 virus was detected. Strikingly, the virus did not cause clinical symptoms in the first bird houses where it was detected. There were clinical symptoms in the houses where it was detected later on, however. There was a drop in feed intake, increased mortality and an extremely severe drop in production of over 80 per cent. The three farms were blocked while the virus was present, rather than having their flocks culled. 

More information

In this report you can also find more information on:

• Clinical Salmonella Enteritidis among laying hens
• Increased reports of cloacitis
• Animal health barometer for poultry

 

Read the highlights report