Avian influenza is a notifiable viral disease that significantly impacts poultry health and welfare, farmer livelihoods, and trade. Biosecurity and management pose a huge challenge due to the wild bird reservoir and in cases of epidemics.
Avian influenza is caused by a virus belonging to the Type A influenza virus. There are many strains of avian influenza and these are grouped into low pathogenic avian influenza (LPAI) and high pathogenic avian influenza (HPAI). LPAI strains may circulate naturally in many wild bird populations, however the virus is capable of mutating into forms that are highly pathogenic. In addition, some avian influenza viruses may infect people and in recent years there has been concern about the potential for a new pandemic in the human population, e.g. HPAI H5N1.
The avian influenza virus may spread from infected birds by direct contact, and faeces, feed and water all being potential means for the virus to spread. Wild birds may be a source for commercial poultry of highly pathogenic forms of the virus. Whilst the spread of avian influenza to people is considered rare, this can happen through direct contact with poultry, contact with contaminated surfaces, or inhalation/ingestion of virus.
Vaccines against avian influenza are available for poultry, including chickens, turkeys and ducks. These may be used in the face of an outbreak or routinely in endemic areas. Consideration must be given to the possible impact of control measures on trade.
As there are different types of the avian influenza virus, so the clinical presentation of the disease may vary. LPAI is associated with few or no clinical signs whereas HPAI is highly contagious and can cause severe clinical signs and high mortality. Clinical signs in poultry may range from mild respiratory signs, reduced egg production and immunosuppression with LPAI, to severe respiratory signs, sudden drop in egg production and up to 100% mortality with HPAI. Other signs may be seen.
EFFECTIVE BIOSECURITY MEASURES ARE ESSENTIAL FOR POULTRY FARMS AND OWNERS OF DOMESTIC BIRDS
THE DISEASE CAN PRESENT IN DIFFERENT WAYS BUT REDUCED EGG PRODUCTION IS SEEN IN BOTH LPAI AND HPAI
HPAI IS HIGHLY CONTAGIOUS AND CAUSES SEVERE CLINICAL SIGNS AND HIGH MORTALITY
Treatment is not an option given the rapid spread and high mortality of HPAI. Preventive measures must be taken to reduce the impact of this disease.
The World Health Organization (WHO) and World Organisation for Animal Health (OIE) work together on international coordination of the control of avian influenza. This includes science-based international guidelines and recommendations, as well as monitoring via the network of reference laboratories. Effective surveillance, including wild birds, is important to increase early disease detection. As with many other diseases, prevention is important, and effective biosecurity measures are essential for poultry farms and owners of domestic birds. These focus on keeping the virus out of contact with poultry, and includes good cleaning and disinfection, barriers to prevent contact with wild birds, and controlling the access of people to poultry buildings. In the event of HPAI outbreaks stamping out is a standard tool to eradicate the virus in many areas, whilst vaccination may also be an option.
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