Avian influenza

It is a notifiable disease and suspect cases must be notified to the local State Veterinary Service Divisional Veterinary Manager. There are two types of avian influenza virus, low pathogenic (LPAI) and highly pathogenic (HPAI). Within the LPAI types there is evidence that certain H5 and H7 viruses may mutate and become highly pathogenic.

History and spread of the disease

Avian influenza was known as “fowl plague”. It first appeared in Italy more than 100 years ago (around 1878). Avian influenza was first recognized in the United States in 1924-25. It occurred again in 1929. It was eradicated both times. Outbreaks due to HPAI were recorded in the Pennsylvania area, USA, in the years 1983-84.

A serious outbreak of HPAI in the Netherlands in 2003, spreading to Belgium and Germany, affected some 250 farms and necessitated the slaughter of more than 28 million poultry.

The H5N1 strain of avian influenza, which surfaced in South East Asia in early 2004, has led to the destruction of millions of birds, and started to spread west through Europe and Africa.

There were also a small number of cases of avian influenza in the USA and Canada early in 2004. The USA strain in Texas was, however, identified as H5N2, not the same as the strain in South-East Asia and the strain in Canada was H7.

A series of wild bird outbreaks have occurred across Europe. The only transfers to domestic poultry have occurred in France, Sweden, Denmark, Germany and Hungary but with early detection and effective control these were eradicated quickly.

Most recent GB outbreaks

The latest information on the current situation is available. Archive of avian influenza incidence in the UK is available.

The disease

– Clinical signs

Typically HPAI presents suddenly with affected birds showing oedema (swelling) of the head, cyanosis (blue discolouration) of the comb and wattles (neck and throat area), dullness, a loss of appetite, respiratory distress, diarrhoea and a drop in egg production. Birds can be infected with LPAI without showing any signs of disease. However, there can be considerable variation in the clinical picture and severity of the disease associated with the type of birds infected and whether birds are also suffering from other diseases. Photos of clinical signs.

The disease

– Transmission

• Wild birds may be implicated in the introduction of the disease to domestic poultry
  
• Direct contact with secretions from infected birds, especially faeces
  
• Contaminated vehicles, equipment, personnel, clothing, water or feed.