www.uzspb.uz  
UZBEKISTAN SOCIETY FOR
THE PROTECTION OF BIRDS
 
Russian

HIGHLY PATHOGENIC AVIAN INFLUENZA H5N1: SITUATION UPDATE SEPTEMBER 2011

Background

Since emerging in 1997 and re-emerging in 2003, highly pathogenic avian influenza (HPAI) H5N1 has had great socioeconomic impacts killing poultry across Asia, Africa and Europe, and causing over 560 confirmed human infections with over 300 resultant deaths. Conservation impacts include direct mortality of birds and indirect impacts such as negative perception of wild birds leading to killing of wild birds and habitat destruction.

Infection has been spread through combinations of movement and trade of poultry and poultry products; traded and/or released pet, farmed or wild birds; and wild bird movements. The relative importance of these routes is often difficult to determine (and will be different in different situations, locations and time periods), however the major route of infection is accepted to be via infected poultry and their products.

Cases of HPAI H5N1 peaked in 2006 and outbreaks declined until mid 2008. Since that time the number of outbreaks has been increasing. Some 63 countries have been affected and although the geographical spread of infection has not changed significantly the disease has re-occurred in countries that have been apparently free of it for some time.

Recent Developments

Influenza viruses including HPAI H5N1 mutate and reassort over time and there are now a number of strains of the virus across the world. In 2011 a new strain (within the 2.3.2.1 clade) emerged and caused poultry mortality in Viet Nam and China. Current vaccines are not entirely effective against this strain.

Both in response to the increase in global cases of HPAI H5N1 and the emergence of the new strain, the Food and Agriculture Organisation of the United Nations warned the global community of the need to maintain a heightened state of readiness and surveillance.

The recent Hollywood film Contagion may also create a resurgence in media interest in the disease and thus it is a timely reminder for relevant organisations' public relations personnel to be well briefed in the issue and current developments.

Role of Wild Birds

Wild birds can be seen as both victims and vectors of the disease. It is likely that poultry infection has spilled over into wild birds on repeated occasions causing small numbers of deaths or large scale mortality events such as that seen at Lake Qinghai in 2005.

Despite the repeated assertion from media and others that wild birds are commonly responsible for long distance spread of infection, extensive surveillance and research has found no 'reservoir' of infection in wild birds. They have undoubtedly been involved in disease spread but research based on known bird movements and ecology and the nature of the infection, suggests that the likelihood of persistent repeated long distance spread is very low. Additionally, outbreaks in wild birds have been apparently self-limiting suggesting the infection does not persist to any great extent (as seen in Europe following extensive outbreaks in 2006 and 2007).

The Task Force therefore considers that wild birds are disproportionally blamed for the spread of infection. Whilst this may have conservation implications, more importantly it can be diversionary (encouraging inappropriate responses that concentrate on wild birds rather than poultry biosecurity and trade issues) and thus does not aid countries in controlling the disease.

The new strain within the 2.3.2.1 clade is no more associated with spread by wild birds than any other prevalent strain.

Scientific Task Force on Avian Influenza and Wild Birds

Supported by: BirdLife International RSPB Darwin Initiative

© Compiled by Oleg Kashkarov
  Webmaster Ernest Khurshut: uznix@narod.ru | Fishes of Uzbekistan
Last modified: 05.10.2011