The Radolfzell bird now appears with a table or Tufted the possible long-distance carriers of avian influenza found in the wild to have (The Independent from 03/09/2006). Mind you, the bird, to which the Asian-variant of the H5N1 virus does not highly pathogenic, and therefore can go undetected over long distances and long periods of transport (without disease outbreaks on the road).
The only study on birds in the field, which can be used for this purpose as a support, and to which the mentioned in Spiegel online "Science" message refers is that of Chen et al. (2006). It is worthwhile to consider such publication in more detail (Inhaltswie reproduction-framed):
13 115 faecal samples of migratory birds (including ducks 4674) were zwischen 2002 und 2005 in Hongkong (n=6.005) und Poyang (n=5.358) gesammelt. Dabei wurden insge­samt 44 Influenza-A-Viren sechs verschiedener Subtypen gefunden (0,34 %), nur 6 Pro­ben hiervon der hoch pathogenenen „Asia-Variante“. Letztere wurden nur in Poyang festgestellt.
Die 6 Proben mit HPAI (hoch pathogener Vogelgrippe) wurden am Poyang-See (Südost-China) bei 2 Probenahmen im Januar und März 2005 von gesund erscheinenden Enten kurz vor ihrem Abzug („apparently healthy migratory ducks … just before their migration north“) isoliert. Dies stellt 0,1 % der dort beprobten Vögel dar.
Das Überleben dieser Vögel wird damit erklärt, that they might have been infected with a harmless H5 virus, antibodies formed against this, and were therefore may be better protected against the highly pathogenic variant.
The birds of Poyang may have been infected by domestic birds in the wintering areas in southern China.
were found in Poyang two different genotypes of the virus ("Z" and "V").
Most of experimentally contaminated with these viruses (laboratory) duck survival data (goose) died and shed virus for up to 7 days also. From this, GE concludes, that the possibility that migrating ducks the virus accommo gene and can spread far.
- In Poyang were found in the 6 birds in the open 2 different genotypes of the H5N1. If the virus within the bird population (which Entenart was infected, or were there several?) To be given, would be of an identical type of virus in each bird individual be assumed. This fact has rather a short pre-infection was carried out by her discharged from various sources viruses. After Johan Mooij (via e-mail) is in the dry season, dry out Poyang Lake is an important rice growing area in which lie several poultry farms where H5N1 outbreaks at the time were recorded.
- In 6005 samples in Hong Kong was not one found with the highly pathogenic organisms, although there migratory birds spend the winter, attracting the various affected areas in East Asia. This shows that no significant vector may exist in the migratory birds. Together with the isolated in Poyang samples were less than 0.05% of the birds, carriers of HPAI. And they were probably infected shortly before.
The similarity of gene segments in January and March in Poyang and has found the disease outbreak in Qinghai (north-central China, May 2005) isolated virus clearly indicates that the ducks das Virus über große Distanzen trans­portieren können (ca. 1.700 km).
- Die Zugvogelbewegungen in China spielen sich überwiegend in Nord-Süd-Richtung ab, nicht jedoch in Ost-West-Richtung. Poyang ist Überwinterungsplatz für Vögel aus Nordost­asien und der vorwiegend östlichen Mongolei. Zugbewegungen zwischen Poyang und Qinghai sind nicht bekannt (Martin Williams per e-mail). Somit spricht auch nichts dafür, dass das Virus von Januar/März 2005 bis Mai 2005 durch Zugvögel von Poyang nach Qing­hai gebracht wurde. Ein Krankheitsausbruch in den mutmaßlichen Durchzugs- und Brutge­bieten der 6 Enten (also approximately north of Poyang) is not known. And no one knows if the birds have lived a long time.
were also in southern China since 2004 51.121 samples of healthy appearing poultry gel taken (on markets). 3051 (6.0%) were found with influenza viruses, including 512 (1.0%) with high high pathogenic H5N1.
in 69 in China and found 52 in Indonesia, Malaysia and Vietnam viruses were sequenced to different regional variants ("regionally distinct sublineages), demonstrating the long-term endemicity in these regions. A key mechanism for this is the transmission from poultry. One of the
in Vietnam in May 2005 was different from the viruses isolated before (but after 2003) in Vietnam and Thailand found, but identical to the in of the Chinese province of Guangxi in May 2005 found. Hence, a transport is by Ge-wing concluded.
The diversity of the genotypes of the virus in some southern provinces reflects the transportation routes of birds.
It is concluded that the best way to combat the epidemic is to implement action at source to be set, held on poultry. Early detection and comprehensive slaughter of animals affected war in Süd-Korea, Japan und Hongkong erfolgreich.
- Die Ausbildung von Endemismen spricht gegen die These der Verbreitung von H5N1 durch Zugvögel. Die verschiedenen regionalen Varianten („sublineages“) in Südchina werden als Nachweis für einen anhaltenden Endemismus gesehen. Es ist auch wenig plausibel, dass neue Regionalvarianten durch Zugvögel induziert werden. Dieses scheinen die Autoren selbst erkannt zu haben, da sie die Vielfalt der in den Tierhaltungen vorgefundenen Genoty­pen und Varianten („sublineages“) als Ergebnis der Transporte von Geflügel zwischen den Provinzen ansehen. Bemerkenswert ist die hohe Durchseuchung des Hausgeflügelbestan­des. Für Thailand adopted the preservation and dissemination of the virus by free grazing domestic ducks (Gilbert 2006).
The work of Chen et al. is seen as evidence of the spread of the virus in the wild possibility by wild birds. In fact, they increased but the doubt on this thesis.
include two further studies on the transmission capability of the statements by HPAI mallard ducks (Hulse-Post et al. 2005, Sturm-Ramirez et al. 2005). These have however been conducted in the laboratory, what with field conditions is not comparable (especially physiological strain of wild birds). By the way, this work is often cited that the duck virus to at 17 Day you can retire after infection, which means a doubling to threefold increase previously determined values. The authors themselves say that this is apparently due to the fact that the ducks were infected with a mixture of viruses. And while the organism deals first with the most common virus, another virus type days after gaining the upper hand and lead to a delayed course of infection. In the field, however, would be from the infection with a type of virus must be considered so the disease would have to be there much faster.
The work of Kou et al. (2005) has several H5N1 viruses after in field sparrows. These are in South China Sedentary and therefore can hardly engage in the transmission.
What is left to suspect migratory birds carry the virus over long distances of? Not much, it is still extremely unlikely. There is as yet no species has been demonstrated that carries the virus without becoming sick from it. If there is a disease outbreak in the wild comes, the birds die within a short time. Where on the proportion of infected but not diseased birds apparently (still) no statement GE can be taken. The virus is apparently difficult in the open in a Vogelorganis mechanism einzudringen, denn der Anteil der erkrankten Vögel an den insgesamt in dem jeweiligen Gebiet vorhandenen Vögeln ist meist recht gering. Das Virus verschwindet jedoch so oder so. Folgeausbrüche nach mehreren Wochen oder Monaten sind noch nicht beschrieben worden.
Die völlig mangelhafte Übereinstimmung der Ausbreitungswege von HPAI von Asien nach Eu­ropa (und Afrika) und dem Vogelzug hat Johann Mooij (per e-mail) detailliert dargelegt.
Dies und auch weitere Fragen lassen die These von (nicht selbst erkrankenden) Zugvögeln („Kaskaden-Enten“) als Vektoren noch unwahrscheinlicher werden:
- Warum kommt es nie zu Folgeausbrüchen? Wenn das Virus in einer Wildvogelpopula­tion should survive, should they occur.
- Why are there along the migration routes of the potential long-distance carrier about any disease outbreaks? Whole scattering pattern of crane in outbreaks could be expected.
- Why are found in open country not carriers of the virus (up to 6 top-called ducks, which had probably become infected even)? And in the meantime more than 100,000 samples tested (Martin Williams via e-mail).
- Why are there where the migratory birds from Asia actually fly in the millions, found throughout the winter no outbreaks in the field?
As a result, we all talk about migratory birds as potential vectors of the spread of avian flu has already cost a lot of time. It has a completely irrational in the population caused Pa-nik. It has led to a negative attitude towards the wild birds. The measures against the entry of the disease by migrating birds has urged the small animal husbandry and welfare of poultry in a corner. It is a cynicism that the Mas-sentierhaltung, which for the emergence and spread of HPAI probably responsible, now benefits from the fact that the competition is eliminated.
And the accusation of migratory birds is from the much more probable Pathways and the important question distracted: How is the virus is in the countryside have been introduced? What transport of poultry or poultry products are responsible for this? The seizure of 55 tonnes of poultry meat from China in mid-Janu-ary Antwerp is just a light on the possible trade routes (for more information on the possible dissemination of aquaculture to Europe see Feare 2006).
Clement Steiof
Chen, H. et al. (2006): Establishment of multiple sublineages of H5N1 influenza virus in Asia: Implications for pandemic control. – PNAS 103 (8): 2845-2850. www.pnas.org/cgi/doi/10.1073/pnas.0511120103
Feare, C.J. (2006): Fish farming and the risk of spread of avian influenza. www.birdlife.org/action/science/species/avian_flu/index.html
Gilbert, M. (2006): Free-grazing Ducks and Highly Pathogenic Avian Influenza,
Hulse-Post, D.J. (2005): Role of deomestic ducks in the propagation and biological evolution of highly pathogenic H5N1 influenza viruses in
Kou, Z. et al. (2005): New Genotype of Avian Influenza H5N1 Viruses Isolated from Tree Sparrows in
Spiegel online (9.3.2006): Zugvögel greaten starker unter Verdacht. www.spiegel.de/wissenschaft/mensch/0,1518,405172,00.html
Sturm-Ramirez, K.M. (2005): Are Ducks Contributing to the Endemicity of Highly Pathogenic H5N1 Influenza Virus in
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