Avian influenza (bird flu)

Ziekteverwekker

There are multiple subtypes of the avian influenza virus and these are named according to the nature of two proteins that are present on the surface of the virus: 16 (1-16) different forms of hemagglutinin protein (HA) and nine (1-9) subtypes of neuraminidase protein (NA) are recognised.

Depending on the ability of the subtype to cause disease in poultry (pathogenicity), viruses are further classified as either low or high pathogenic varieties. Mutation can result in a formerly low pathogenic H5 or H7 variant (LPAI) becoming highly pathogenic (HPAI).

Gevoelige diersoorten

Birds – Water birds, in particular Anseriformes (ducks, geese, and swans) and Charadriiformes (sea gulls, sterns and waders) are the natural reservoirs for LPAI viruses. Typically these viruses do not cause serious disease in birds (Verhagen et al., 2015).

In contrast, HPAI-viruses can cause serious disease and mortality in chickens and other bird sorts including Anseriformes. It Is believed that HPAI viruses develop in domesticated poultry in intensive farming conditions and not in wild birds (Pasick & Kahn, 2014).

Occurrences of HPAI demonstrate that at some point genetic material has been exchanged between HPAI H5N1-virus and an LPAI-virus. This is likely to lead to the development of  HPAI viruses that are better adapted to some species of wild birds which, in turn, would facilitate virus spread by wild birds (Verhagen et al. 2015).

Mammals, including people (AI is a zoonosis), dogs, cats, horses and pigs can become infected with AI viruses.  Additionally, in the winter of 2014-2015 variant H10N7 was found in seals in the Netherlands.

Symptomen dieren

Signs in LPAI-infected birds include egg-drop, respiratory problems and an increased mortality rate. Signs are more severe in cases of HPAI infection. In addition diarrhoea, swelling and blue discoloration of the comb, wattle and legs can be seen. In ducks central nervous system signs may occur.

Symptomen mens

People infected with AI develop fluey symptoms including fever, headache, muscle soreness, cough and conjunctivitis.

Besmetting mensen

Infection occurs by direct or indirect contact via the gastrointestinal tract, airways or ocular surfaces.

Voorzorgsmaatregelen

Poultry industry – Biosecurity measures to prevent the spread of AI virus are compulsory for poultry farmers and live-animal transporters.

In addition, poultry farms are monitored in order to facilitate the detection of AI infection at an early stage. When AI infection is suspected, infected premises are put under movement restrictions while further investigations are carried out.

Monitoring is also performed in wild bird populations. Surveillance of live birds allows researchers from the Dutch Center for Field Ornithology (Sovon) and the Erasmus Medical Centre, to keep track of which AI viruses are circulating. Europe-wide monitoring of AI in dead birds and living wild birds was instigated after HPAI H5N1 was detected in Europe in 2005 and 2006. It was then associated with mortality in wild birds, particularly the mute (Cygnus olor) and Bewick (Cygnus cygnus) swans.

In the Netherlands the DWHC, Sovon, Central Veterinary Institute (CVI) and the NVWA (Dutch Food and Consumer Product Safety Authority) are involved in this monitoring program.

Sources

Pasick J, Kahn S. The scientific rationale for the World Organisation for Animal Health standards and recommendations on avian influenza. Rev Sci Tech. 2014 Dec;33(3):691-709.

Verhagen JH, Herfst S, Fouchier RA. Infectious disease. How a virus travels the world. Science. 2015 Feb 6;347(6222):616-7. doi: 10.1126/science.aaa6724.

Onderzoeksresultaten

• Less reports but bird flu still prevalent (30/07/2024)
• Despite ongoing presence of the avian influenza virus, no major outbreaks in 2024 yet (18/04/2024)
• Occurrence of bird flu is currently low, but stay vigilant (08/02/2024)
• Is it still important to send in dead wild birds for bird flu surveillance? (23/01/2024)
• Avian influenza circulating among wild birds again (17/11/2023)
• A Sparrowhawk Accipiter nisus with multiple health problems (29/06/2023)
• Update on mortality in black-headed gulls (23/03/2023)
• Keep a look-out for Avian Influenza in black-headed gulls (20/02/2023)
• Two foxes in east of Groningen diagnosed with Avian influenza virus (03/06/2021)
• Update avian influenza (09/03/2021)
• Highly pathogenic strain of avian influenza (bird flu) still present among wild birds. (20/01/2021)

Projecten

Geen projecten gevonden.

Overige berichten

• Results of research on foxes in Friesland (26/01/2026)
• Optimizing bird flu surveillance in wild carnivores and scavenging mammals (05/01/2026)
• An outbreak of bird flu: what to do? (08/12/2025)
• H5N1 virus widespread among wild birds again (18/11/2025)
• Situation of bird flu outbreak: first positive test results (10/11/2025)
• Investigation ongoing into reports of birds with signs of bird flu in the north of the Netherlands (16/10/2025)
• Bird flu found at poultry farm in Drenthe (07/10/2025)
• Focus species 2025: results of the first half of the year (03/07/2025)
• Is mortality among wild birds caused by bird flu increasing again? (27/06/2025)
• Bird flu present into the breeding season (08/05/2025)
• Bird flu found in Common Kestrel (04/03/2025)
• Bird flu seems to be spreading (24/02/2025)
• Increased vigilance regarding mammals in relation to bird flu (04/02/2025)
• Again many wild birds affected by bird flu (24/01/2025)
• Bird flu found in fox (23/01/2025)
• Keep a look-out for bird flu (06/12/2024)
• HPAI found in wild birds and poultry (04/12/2024)
• Alaska: Polar bear dies from bird flu (04/01/2024)
• Map of wild birds with avian influenza (20/12/2020)

Documenten en Publicaties

• Effect of 2020–21 and 2021–22 Highly Pathogenic Avian Influenza H5 Epidemics on Wild Birds, the Netherlands. Caliendo, V., E. Kleyheeg, N. Beerens, K.C.J. Camphuysen, R. Cazemier, A.R.W. Elbers, R.A.M. Fouchier, L. Kelder, T. Kuiken, M. Leopold, R. Slaterus, M.A.H. Spierenburg, H. van der Jeugd, H. Verdaat & J.M. Rijks (2024). Emerging Infectious Diseases. 2024;30(1):50-57. doi:10.3201/eid3001.230970.

• Zoonotic Mutation of Highly Pathogenic Avian Influenza H5N1 Virus Identified in the Brain of Multiple Wild Carnivore Species. Vreman, S., M. Kik, E. Germeraad, R. Heutink, F. Harders, M. Spierenburg, M. Engelsma, J. Rijks, J. van den Brand & N. Beerens. Pathogens 2023, 12(2), 168; https://doi.org/10.3390/pathogens12020168