Avian influenza (bird flu)

What is bird flu or avian influenza?

Avian influenza (AI) is also known as bird flu. It is a collective term for several influenza viruses. Especially chickens, turkeys, waterfowl, waders, beach birds, ratites and starlings are susceptible to avian influenza. Avian influenza has two variants: a mild and a hazardous variant. Most viruses are of the mild variant; Low Pathogenic Avian Influenza (LPAI). Chickens infected with LPAI viruses exhibit few disease symptoms. However, LPAI viruses of types H5 or H7 can adapt (mutate) into a highly pathogenic variant; Highly Pathogenic Avian Influenza (HPAI). In chickens infected with HPAI viruses, very serious disease is seen, with up to 100% mortality.

Can avian flu affect humans?

Some types of bird flu are transmissible to humans (zoonosis). The chance of humans becoming infected is small, and if it does happen the symptoms are usually very mild. However, it is important to prevent infections as much as possible. The bird flu virus could adapt itself (by mutation), after which it could also spread between people. Therefore we strongly advise to avoid direct contact with sick and dead wild birds and poultry.

How does bird flu spread?

Avian influenza is transmitted by infected wild (water) birds and their faeces. The risk for poultry that can roam outside is therefore much higher. As more and more poultry is kept in free-range conditions, the risk of bird flu in the Netherlands will increase. The (illegal) import of ornamental birds also constitutes a risk. The risk of bird flu entering the Netherlands via the import of poultry, hatching eggs and poultry products is probably small. A monitoring programme for avian influenza in the Netherlands is running, so that we can quickly trace new introductions.

Birds, including poultry, can catch bird flu in several ways:

• Through direct contact with infected birds or faeces; the virus can be spread through the respiratory system, eye fluids and droppings
• Through contaminated materials such as food, crates, vehicles and people who have been in contact with the virus through their shoes or clothing
• Via dust from a contaminated coop (spread through the air)

Can poultry farmers take preventive measures?

It is impossible to prevent the infection of wild birds. However, farmers can take a large number of measures to decrease the risks of potential contamination. The virus can be kept from affecting stables by putting in place bio-safety measures. Implementing and following up these measures requires perseverance and strict discipline. Businesses such as breeding farms that are higher up in the pyramid, generally invest more in bio-safety. These companies are seldom affected by avian flu.

Within the European Union legislation exists to prevent avian influenza from being introduced or spread via infected poultry or transport.

Vaccination of poultry is possible but there are many snags to it.

Read more:

• Four considerations in the discussion whether to vaccinate against bird flu

What research on avian flu does WBVR do?

Wageningen Bioveterinary Research (WBVR) is the designated institute in the Netherlands that performs diagnosis of avian influenza. With laboratory tests our experts can see if the virus is present and run diagnostics on samples of poultry from locations where a bird flu suspicion is present. We also examine wild birds and waterfowl in order to rule out avian influenza as a cause of the birds’ death. The goal is to identify the disease as early as possible and then check the poultry kept in the surroundings.

WBVR studies the origin of avian flu by analysing the genetics of new strains in the Netherlands. Comparative studies are done to investigate whether individual cases on different farms show similarities or differences, to map the transmission route. Furthermore, our scientists study the introduction of avian flu on poultry farms in general, and free-range farms in particular, in the Netherlands. We also test new methods to keep wild (aquatic) birds away from the enclosures.

Since the HPAI H7N7 outbreak in 2003, The Netherlands has a monitoring program. Domestic poultry, but also wild birds, are regularly checked for antibodies by WBVR. In this way, it is possible to discover avian influenza at an early stage and limit the spread of the virus (early warning programs).

WBVR can also test if desinfectants are able to inactivate the avian influenza virus.

Read more:

• Diagnostics by WBVR

• Disinfectant testing by WBVR

• Bird flu - who does what in the Netherlands? (pdf)

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