Avian Influenza


Avian Influenza
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Avian Influenza or Bird Flue The Facts

Avian Influenza (also known as Bird Flu or Fowl plague) is a highly infectious viral disease, affecting the respiratory, digestive and/or nervous system of many species of birds.  Avian Influenza is a notifiable poultry disease, which if you suspect may be present on your farm, must be relayed immediately to Defra.  It is then the legal responsibility of Government to control the disease through the slaughtering of infected flocks, imposition of movement restrictions and monitoring (3km restriction zones and 10km surveillance zones)

Avian Influenza is caused by a Type A influenza virus.  There are two types, low pathogenicity (LPAI) and high pathogenicity (HPAI).  LPAI has been found to be present in some areas of the global wildfowl but does not always show clinical symptoms.  There is a low risk of migrating birds bringing LPAI to the UK.  Of more concern is the potential of some LPAI strains to mutate into HPAI, especially when introduced into poultry populations.

Most outbreaks have originated from migrating waterfowl passing the infection to local wild bird species, which in turn, pass it to domestic poultry, especially those kept outdoors.

Spread from bird to bird within a flock is via faeces, saliva and exhaled moisture droplets containing virus particles.  Research has also shown that any infection is made worse by poor environmental factors such as dust, ammonia, concurrent infection with other pathogens, such as Mycoplasmas, E.coli, other respiratory viruses and also the age of the bird, species and any nutritional deficiencies

An important point to make is that avian influenza is a disease of birds caused by influenza viruses closely related to human influenza viruses. However, the major concern in relation to avian influenza is the possibility of the avian virus transforming to a human influenza virus.  In South East Asia, where millions of poultry have been infected and slaughtered, only a small number of people have died after having been in very close contact with diseased or dying birds.  

The NFU have been working closely with Defra, together with a number of stakeholders to develop a workable contingency plan and communication link, should we have to deal with an outbreak.


       Direct contact with secretions from infected birds, especially faeces
       Contaminated feed, water, equipment and clothing
       Clinically normal waterfowl and sea birds may introduce the virus into flocks
       Broken contaminated eggs may infect chicks in the incubator

How do I minimise the risks?

Maintaining high levels of bio-security on farm is key to the control of this disease.  Transmission of the virus can be minimized by limiting the movement of people and machinery onto sites and where possible limiting contact with other poultry, waterfowl and pigs. 

The main points:

       Careful monitoring of poultry to enable early detection of changes in behaviour and feed consumption is essential.  Other changes to look out for include increased levels of mortality, respiratory signs, changes in water and feed consumption and drop in egg quality and production levels

       Prompt consultation with your veterinary surgeon if you have any concerns
       Ensure that wild birds, dogs, cats, rodents are excluded from poultry houses
       Use of foot dips and change of overalls/footwear.  All visitors to the Poultry Unit must adhere to this requirement

       Any feed spillages that occur around a feed bin should be immediately cleaned up to avoid wild birds congregating in that area

       Poultry must have access to a supply of clean, fresh drinking water.  Access to standing water must be restricted to free range birds, as this may potentially have been contaminated by wild birds


Birds infected with avian influenza have been known to exhibit a wide variety of symptoms, which may manifest as sudden high mortality with no prior warning.  However, other clinical symptoms include:

       Onset of respiratory noises/respiratory distress
       Excessive fluid leakage from the eyes and nostrils
       Oedema (swelling) of the head, neck and around the eyes
       Combs and wattles may become dark in colour (Cyanosis), due to subcutaneous hemorrhaging
       Diarrhoea bright green changing to white
       Drop in or cessation of egg production
       Dullness and lack of appetite
       The area between the hocks and feet may show signs of diffuse hemorrhaging
       Marked depression

Further information:

The websites listed below contain useful advice and information on avian influenza, in terms of both human and animal health:



Health Protection Agency


World Health Organisation






Latest news on Europe:




Food Standards Agency


Department of Health


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This site was last updated 10/19/05