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Topic: Birdlife position statement on Bird Flu 國際鳥盟的公告 (Read 1027 times) |
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HF_Cheung
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Birdlife position statement on Bird Flu 國際鳥盟的公告
« on: Aug 31st, 2005, 5:38pm » |
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I receive the position statement of Birdlife International on Bird Flu. Members may like to take a look on this.
HF Cheung
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Avian Influenza 'Poultry flu': BirdLife Position Statement
25 August 2005
The numerous strains of avian influenza can be divided into two classes, according to their pathogenicity (disease-causing ability) to domestic poultry. [a] Low pathogenic strains circulate in wild birds, especially waterbirds, usually at low levels. These cause no, or only mild, illness. However, strains of the H5 and H7 subtypes can occasionally become highly pathogenic following a specific mutation. These highly pathogenic viruses can cause great mortality in domestic poultry flocks but are very rare in wild birds, with only one recorded instance prior to 1997 when the current strain of concern, H5N1 appeared.
Poultry flu, H5N1, is highly pathogenic. Genetic evidence clearly points to it originating in domestic birds through mutation of low pathogenic sub-types of avian flu. Subsequently, H5N1 has been passed from poultry to wild birds on several occasions, and as the disease spreads, these instances are likely to become more frequent.
Transmission is promoted in domestic flocks due to the density of birds and the consequent close contact with faecal and other secretions that contain the virus. Husbandry methods like those in SE Asia, where domestic flocks are often allowed to mix freely with wild birds, especially waterfowl, make the transmission to migratory waterbirds easier.
The H5N1 virus is spreading, with recent outbreaks in China, Kazakhstan, Mongolia and several regions of Russia, on top of the spread through SE Asia since the end of 2003. It is not yet clear how the disease is spreading: movement of domestic birds is likely to have a significant role, and migrating waterbirds may also be involved. Evidence suggests the outbreak in China had its origins in domestic birds. However, there is a recent instance, in Kovsgol Province, Mongolia, where poultry flu has been detected in wild migratory birds that had no apparent contact with domestic poultry. There, as in other outbreaks in wild birds, the disease was quickly self-limiting. Around 100 out of 6,500 waterfowl at the lake died, and tests on 139 live birds at this and a nearby site all proved negative for the virus. [b]
The points below are based on the best information available on 25 August 2005:
There have been no recorded instances of transmission of the disease between infected wild birds and humans. The H5N1 virus strain is not currently contagious between humans and most human cases to date have been associated with close contact with infected domestic poultry. The risk of a human contracting the disease from a wild bird is remote, unless there was excessive close contact with infected birds and their excreta.
Wildlife and health experts (including the World Health Organization, Food and Agriculture Organization of the United Nations, and World Organisation for Animal Health) are agreed that culls of wild birds are highly unlikely to stop the spread of the disease. Indeed, they are certain to be counterproductive in encouraging birds to disperse widely. Moreover, culls would divert resources away from important disease control measures. [c]
The most efficient control techniques involve improved biosecurity, primarily of the poultry industry, to reduce the likelihood of contact between domestic stock and wild birds or infected water sources. This needs to be coupled with swift and complete culls of infected poultry flocks in the event of an outbreak. Further measures that should be considered include strengthening surveillance for the disease, and stricter controls on wild bird markets and movements of domestic poultry. Such measures should be introduced worldwide. Countries currently free of the disease should consider a ban on imports of domestic poultry, wild birds for the pet trade and untreated bird products (feathers, fresh meat etc) from affected regions. Preventing public access to infected sites is also clearly a sensible precaution.
We fully recognise the potential for a human pandemic should the current viral strain increase its transmissibility through mutation or reassortment, thus facilitating human to human transfer of the disease. We also recognise the impact the current strain is having on local economies forced into culls of domestic flocks. The considerations highlight the need for the limited resources available to be focused on the places and activities where people, livestock and wildlife come into close contact.
In addition to the impact of the disease on economics and livelihoods, and the potential impacts for human health, there are potential implications for conservation. For instance, it is estimated that somewhere between 5% and 10% of the world population of the Bar-headed Goose Anser indicus perished in the recent outbreak in China.
Notes:
a. At least 135 strains are recognised, based on the combination of different H and N subtypes
b. www.mydna.com/resources/news/200508/news_20050819_birsam.html
c. The World Heath Organization (WHO), The Office International des Epizooties (OIE) and the Food and Agriculture Organization (FAO) all concur that "the control of avian influenza infection in wild bird populations is not feasible and should not be attempted." (www.who.int/csr/don/2005_08_18/en/index.html)
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Webcreeper
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Re: Birdlife position statement on Bird Flu 國際鳥
« Reply #1 on: Sep 1st, 2005, 12:01am » |
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禽流感“家禽流感”：來自國際鳥盟的公告
25/8/05
禽流感病毒品種繁多（註一），可因其對家禽的致病能力分為兩種。低致病性的病 毒會在野鳥之間傳播，尤其是水鳥，流傳程度一般不高，不會令野鳥生病，或只會 引起小病。可是在經過某種突變之後，H5和H7病毒亞種有時會產生極高的致病能力 ，這些高致病性病毒會令大量家禽死亡，但是對野鳥卻沒有大影響（在1997年H5N1 品種出現之前只有一宗紀錄）。
H5N1家禽流感致病能力甚高，基因分析顯示它來自由人飼養的雀鳥，由低致病禽流 感病毒經突變產生。生成之後，這種病毒曾多次傳到野鳥身上。隨著病毒日益擴散 ，傳染野鳥的事例可能會愈來愈多。
由於家禽高度密集，禽鳥間緊密接觸，交換含有病毒的糞便和其他分泌物，大大助 長了病毒的傳播。在東南亞的飼養方法，往往讓家禽和野鳥（尤其是水鳥）自由混 在一起，很容易便會將病毒傳給遷徙中的水鳥。
H5N1病毒正在擴散，除了自2003年起在東南亞開始散播之外，最近在中國、卡薩克 斯坦、蒙古以及俄羅斯數個地方也有爆發。病毒擴散的方法至今未明：家禽運輸可 能是重要因素，而遷徙的野鳥也可能有關。有證據顯示在中國爆發的病例來自人養 的雀鳥。可是，在最近一宗在蒙古Kovsgol省發生的病例中，卻在看來沒有和家禽 接觸過的野鳥身上驗出家禽流感。就如其他在野鳥間爆發的案例一樣，該次疫情很 快便自動竭止。在湖裡的6,500隻雀鳥中有100隻死亡，人們對139隻在現場及附近 的活鳥做了測試，沒有發現病毒（註二）。
下文根據在2005年8月25日所得的最新資料撰寫：
至今沒有野鳥將禽流感傳給人類的案例紀錄。目前的H5N1病毒並不會在人類之間傳 播，而大部份的人類感染個案都和與染病的家禽緊密接觸有關。除非人類與病鳥及 牠們的糞便有過度親密接觸，否則人類從野鳥身上感染禽流感的機會甚微。
野生生物和衛生專家（包括世界衛生組織、聯合國食物及農業組織、世界動物健康 組織等）都同意，集體撲殺野鳥對制止病毒擴散功效不大，適得其反，此舉肯定會 令雀鳥更廣泛地擴散。再者，撲殺行動也會分薄給其他重要防疫措施的資源（註三 ）。
最有效的防疫措拖是改善生物防禦，特別是家禽飼養業，減少家禽和野鳥或受感染水源接觸的機會，同時，還需要在疫情爆發時立即及徹底的撲殺已經受感染的家禽。其他應考慮採納的措施包括加強對疫情的監察、加強監管野鳥賣買和家禽運輸，值得在全球推行。還未受到家禽流感波及的國家應考慮禁止從疫區輸入家禽、用作寵物的野鳥和未經過處理的鳥類產品（如羽毛、鮮肉等）。禁止人民進入疫區，亦是非常合理的預防措施。
我們非常了解，目前的病毒品種可能會經過基因突變或基因重組，增加人傳人的能力，演變為一場在人類間廣泛傳播的傳染病。我們也知道由於被逼要撲殺家禽，令一些地區的經濟飽受衝激。我們因此更加要將有限的資源集中到人類、禽鳥和野鳥有緊密接觸的地點和活動之上去。
家禽流感除了威脅人類的經濟、生計和健康之外，還可能會影響到自然保育，一個 例子是：估計全球百分之五到十的斑頭雁最近在中國爆發的疫情中死去。
備註：
一 根據不同的H和N亞種組合，經確認的最少有135個品種。
二 www.mydna.com/resources/news/200508/news_20050819_birsam.html
三 世衛組織、The Office International des Epizooties (OIE，世界動物健康組織) 和聯合國食物及農業組織都同意「控制在野鳥之間傳播的禽流感並不可行，而且也不應嘗試。」(www.who.int/csr/don/2005_08_18/en/index.html)
W 中譯
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