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Definition: avian influenza from The Macquarie Dictionary
1.

any of a wide range of influenza viruses affecting birds, some strains of which, such as the H5N1 virus, are transmittable from birds to humans, this being recognised for the first time in Hong Kong in 1997.


Summary Article: Avian Influenza
from Black's Veterinary Dictionary

Avian influenza (it used to be called fowl plague, but the term is no longer used) attacks domesticated fowl chiefly, but turkeys, geese, ducks and most of the common wild birds are sometimes affected. It is not known to affect the pigeon. The disease is found in Asia, Africa, the Americas and to a lesser extent in parts of the continent of Europe, and is always liable to be introduced to countries hitherto free from it through the migrations of wild birds. An outbreak occurred among turkeys in Norfolk in 1963; this was the first recorded outbreak in Britain since 1929. An outbreak occurred in the Republic of Ireland in 1983; a slaughter policy followed. Infection may have come from Pennsylvania, where a similar policy was adopted.

Already in this century, there have been outbreaks of a severe form of the disease in the Netherlands, Belgium and Germany (2003) and milder outbreaks in the Americas in 2004. However, in 2004 and 2005, there was a severe series of outbreaks caused by H5N1 strain in South East Asia, Japan, China and Korea, with spread to, and mortality in, the human populations. Unusually, this virus can also infect felidae. The EU stopped all imports from the area. As a result, the OFFICE INTERNATIONAL DES EPIZOOTIES proposed a new definition of avian influenza: ‘infection by an influenza A virus that has intravenous pathogenicity index in 6-week old chickens greater than 1.2 or any influenza virus of H5 and H7 subtype.’ ‘Poultry’ covers all birds kept in captivity for the production of meat or eggs, for restocking game or for breeding.

Cause

Myxovirus influenzae.

Signs

In some cases the number attacked is small, while on the same premises the next year 80 per cent or 90 per cent of the total inhabitants of the runs may die. The affected birds often die quite suddenly. In other instances the sick birds isolate themselves from the rest of the flock, preferring some dark out-of-the-way corner where they will be undisturbed. They are dull, disinclined to move, the tail and wings droop, the eyes are kept closed; the bird may squat on its breast with its head tucked under a wing or in amongst the shoulder feathers; food is refused, but thirst is often shown; the respirations are fast and laboured but not impeded by mucus; the temperature is very high at the commencement (43° C to 44° C [110°F to 112° F]), but falls shortly before death to below normal. (The normal temperature of birds is 41° C [106.5° F].) The comb and wattles become purple or blue and oedema of the head and neck is common. The illness seldom lasts more than 24 to 36 hours, and often not more than six.

Control

Vaccines are available but their use is incompatible with an eradication policy. They are used in parts of the USA and in Italy.

© Edward Boden and Anthon Andrews, 2015

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