Herbstvogelzug und Verschärfung der Stallpflicht
Diskutiere Herbstvogelzug und Verschärfung der Stallpflicht im Vogelgrippe / Geflügelpest Forum im Bereich Allgemeine Foren; Im folgenden die wissenschaftliche Bewertung einer Impfaktion in Hongkong, durchgeführt vor einigen Jahren. Die Impfung erfolgte in einem zeitlich und geographisch eng begrenzten Rahmen. Nachdem ...
- 25.09.2006, 12:00 #81
Nachdem einige der oben angesprochenen Aspekte thematisiert werden, stelle ich einen grösseren Teil des Papiers ungekürzt ein.
Vaccination of chickens against H5N1 avian influenza in the face of an outbreak interrupts virus transmission
Trevor M. Ellis1,+, Connie Y. H. C. Leung2, Mary K. W. Chow3, Lucy A.
One of the concerns in the use of vaccine to control HPAI in poultry farms is the possibility that while vaccine may protect from disease, asymptomatic virus circulation may continue, resulting in spread of infection to other farms. The monitoring and surveillance conducted on these three chicken farms showed that use of this killed H5N2 vaccine in the face of HPAI H5N1 virus challenge was able to protect chickens from disease and interrupt virus transmission. The protective effect of vaccine became apparent after day 18 post-vaccination. On farms 1 and 2, clear evidence of H5N1 infection was demonstrated in sheds of vaccinated chickens,and subsequently extensive surveillance by clinical inspection and virus detection tests, both H5 RRTPCR and virus culture, showed that the virus transmission had been interrupted. For farm 3, the rapid depopulation of the affected shed and strict biosecurity measures applied combined to minimize the level of challenge to other sheds. No evidence of clinical disease or H5N1 infection was demonstrated in the sheds of vaccinated chickens so it is possible that the other sheds on this farm may not have received significant exposure to the H5N1 virus from the initial infected shed. Vaccines have been used in other countries to assist in the control of avian influenza. Countries that have used vaccines for avian influenza control include Italy (Capua et al. , 2002), the US (Halvorson, 2002), Mexico (Villarreal & Flores, 199 and Pakistan (Naeem, 199. Mostly vaccination has been directed against low pathogenic strains of avian influenza virus but Mexico and Pakistan have successfully used vaccine against highly pathogenic H5 or H7 avian influenza viruses. Experimental studies have shown that commercially available H5 avian influenza vaccines could protect poultry from 1997 Hong Kong strains of H5N1 HPAI virus (Swayne et al ., 2001). On Farm 2, avian influenza H9N2 virus was detected in the sheds containing 16-day-old to 32-day-old chickens. Recent experimental studies have suggested that infection with H9N2 virus may stimulate cell-mediated immune responses that could cross-protect chickens from intranasal H5N1 virus challenge that was lethal in uninoculated controls (Seo & Webster, 2001). This crossprotectivity was effective at 15 days after intranasal inoculation with H9N2 virus given in a low challenge dose (10 50% lethal chicken doses), but its effectiveness was diminished by 30 days postinoculation. Infection of chickens with H9N2 avian influenza viruses is quite common in chickens in Hong Kong based on monthly serological surveillance conducted by our laboratories on local and imported chickens between 1999 and 2001. The H9N2 viruses isolated from chickens in Hong Kong belong to a lineage of viruses related to A/ Duck/Hong Kong/Y280/97 (H9N2) (Guan et al., 2000), which generally causes mild or inapparent infections of the upper respiratory tract in chickens. On local farms where H9N2 infection has been monitored, it generally occurs in chickens under 30 days that are reared on litter. By the time they are moved to the A-frame cages infection is less common and chickens of multiple ages on affected farms are H9N2 antibody positive. On farm 2 with H9N2 infection circulating in the 16-day-old to 32- day-old birds it would be highly probable that the older birds (39 to 46 days old) in sheds 1 and 3 would have been exposed to this virus, but this did not prevent the H5N1 outbreak in these sheds. During the 2002 H5N1 outbreak on chicken farms in Hong Kong there appeared to be no correlation between exposure to H9N2 virus, measured by serology, and the severity of the outbreak. The H9N2 AI virus exposure and resulting immunity had no protective effect against the field challenge by H5N1 AI virus possibly because of either shortlived shortlived cross-protective cellular immunity or a high environmental challenge dose of H5N1 AI virus. Avian influenza vaccination has generally been used in uninfected flocks in control areas around but not including infected flocks. From this investigation we are definitely not suggesting that the use of vaccination to assist in the control of an avian influenza outbreak could be delayed in the control area until evidence of spread from infected farm(s) occurs. Nor do we recommend the use of partial depopulation plus vaccination on an infected farm as a normal practice. In the first Tai Kong Po farm, five sheds with 22 000 chickens had to be killed before vaccination had a chance to work in the final shed, and in the meantime outbreaks occurred on two nearby farms that were ring vaccinated at the same time as the initial farm. Generally, when ring vaccination is used for avian influenza control, the infected farm and highrisk contact farms within an epidemiologically sustainable perimeter (usually several kilometres) are quarantined, monitored and possibly depopulated. Ring vaccination is used outside this zone where there is a good chance for immunity to develop to the virus before exposure occurs. The close proximity of farms and limited land availability makes this approach difficult in Hong Kong. For the three farms involved in this investigation the individual circumstances at the time, together with expanding use of preventative vaccination throughout Hong Kong, led to an unusual control strategy involving quarantine, partial depopulation and vaccination of unaffected sheds and surrounding farms. As part of this strategy very strict attention had to be paid to movement control of birds, people and materials onto and from the farm and strict biosecurity practices had to be maintained. This was combined with an intensive monitoring programme on the vaccinated sheds and the surrounding farms to rapidly detect any spread of the infection. This strategy was very resource intensive and would have been very difficult to sustain in a more widespread outbreak. Another factor that should be considered with vaccinating in the face of an outbreak is the possibility of selection of variant viruses when the virus is replicating rapidly in the presence of partial or incomplete flock immunity. The chance of this occurring will clearly be lower if virus is introduced to a fully vaccinated flock that has had time to develop its immunity. However, concerns expressed about the risk of enhanced H5N1 virus evolution in the presence of a vaccinated antibody-positive chicken population needs to be kept in perspective. If you do not vaccinate, all exposed chickens have the potential to become infected with H5N1 viruses that will replicate to high titres and shed large quantities of virus in faeces and respiratory secretions that will infect further chickens. Each replication cycle increases the number of mutations and 410 T. M. Ellis et al.
the potential for antigenic variation. There are also many examples of emergence of HPAI avian influenza viruses from low or medium pathogenic avian influenza viruses without any influence from vaccination (Alexander et al., 2000). Inactivated oil emulsion avian influenza vaccines have given good protection despite variation of up to 10.9% in haemagglutinin-deduced amino acid sequence (Swayne et al., 1999, 2000). Avian influenza vaccination has been most widely practiced in Mexico, beginning in January 1995, and it continues to be used. Over 1.4 billion doses of inactivated vaccine and 500 million doses of fowlpox-AI-H5 recombinant vaccine have been used and the vaccines are still considered protective (Villarreal-Chavez & Rivera-Cruz, 2003). The ultimate goal of any control programme for avian influenza should be to eradicate HPAI. This was also the goal in Hong Kong during this outbreak, and this goal was achieved. With the presence of these viruses in wild water birds in the region and the large daily cross-border movement of poultry the risk of H5N1 virus incursions infection in Hong Kong is very high. A comprehensive package of measures including enhanced biosecurity programmes for farms, wholesale and retail poultry markets, the use of rest days in markets to break cycles of infection and a comprehensive monitoring and surveillance programme for early detection of any H5 avian influenza virus incursions have been in place since 2001 and were enhanced after the February to April 2002 outbreak. As stressed by international animal health authorities (Alexander et al ., 2000), avian influenza vaccination in Hong Kong is used to complement the strict biosecurity measures and a comprehensive monitoring and surveillance programme already in place. Comprehensive vaccination of all chicken farms supplying the local retail markets was introduced as an additional layer of protection after a one year long vaccination evaluation trial (Ellis et al., 2004b). This investigation showed that the use of killed H5N2 vaccine on three farms undergoing H5N1 HPAI outbreaks was able to protect chickens against disease and also to interrupt asymptomatic virus shedding. This is particularly relevant when dealing with viruses such as H5N1 where the virus also poses a significant risk to human health.
Acknowledgements The authors thank the staff of the Avian Influenza Serology, Avian Virology, Molecular Biology, Histology and Bacteriology laboratories at Tai Lung Veterinary Laboratory, the staff of the Department
of Microbiology, University of Hong Kong and the field staff of Livestock Farm Division for their excellent technical support. The studies at The University of Hong Kong were supported by The Wellcome Trust Grant 067072/D/02/Z and a Public Health Research Grant AI95357 from the National Institutes of Allergy and Infectious Diseases.
Alexander, D.J. (2000). Highly pathogenic avian influenza. In OIE
Manual of Standards for Diagnostic Tests and Vaccines 4th edn (pp.
212 _/220). Paris: Office International des Epizooties.
Alexander, D., Meulemans, G., Kaleta, E., Capua, I., Marangon, S.,
Pearson, J. & Lister, S. (2000). Definition of avian influenza: the use
of vaccination against avian influenza. In Report of the Scientific
Committee on Animal Health and Welfare of the European Commission
Capua, I., Terregino, C., Cattoli, G., Mutinelli, F. & Rodriguez, J.F.
(2002). Development of a DIVA (Differentiating Infected from
Vaccinated Animals) strategy using a vaccine containing a heterologous
neuraminidase for the control of avian influenza. Avian
Pathology, 32, 47_/55.
Ellis, T.M., Bousfield, R.B., Bissett, L., Dyrting, K.C., Luk, G.S.M.,
Tsim, S.T., Sturm-Ramirez, K., Webster, R.G., Guan, Y. & Peiris, J.S.
(2004a). Investigation of outbreaks of highly pathogenic H5N1 avian
influenza in waterfowl and wild birds in Hong Kong in late 2002.
Avian Pathology (in press).
Ellis, T.M., Sims, L.D., Wong, H.K.H., Bissett, L.A., Dyrting, K.C.,
Chow, K.W. & Wong, C.W. (2004b). Evaluation of vaccination to
support control of H5N1 avian influenza in Hong Kong. In G. Koch
& R. Schrijver (Eds.), Wageningen UR Frontis Series: Avian influenza,
prevention and control . Dordrecht: Kluwer Academic Publishers (in
Guan, Y., Shortridge, K.F., Krauss, S., Chin, P.S., Dyrting, K.C., Ellis,
T.M., Webster, R.G. & Peiris, M. (2000). H9N2 influenza
viruses possessing H5N1-like internal genomes continue to circulate
in poultry in southeastern China. Journal of Virology, 74 , 9372 _/
Guan, Y., Peiris, M., Kong, K.F., Dyrting, K.C., Ellis, T.M., Sit, T.,
Zhang, L.J. & Shortridge, K.F. (2002). H5N1 influenza viruses
isolated from geese in southeastern China: evidence for genetic
reassortment and interspecies transmission to ducks. Virology, 292 ,
Halvorson, D.A. (2002). The control of H5 or H7 mildly pathogenic
avian influenza: a role for inactivated vaccine. Avian Pathology, 31 ,
Naeem, K. (199. The avian influenza H7N3 outbreak in South
Central Asia. In D.E. Swayne & R.D. Slemons (Eds.), Proceedings of
the 4th International Symposium on Avian Influenza (pp. 31 _/35.
Athens, GA, USA.
Seo, S.H. & Webster, R.G. (2001). Cross-reactive, cell-mediated
immunity and protection of chickens from lethal H5N1 influenza
virus infection in Hong Kong poultry markets. Journal of Virology,
75 , 2516 _/2525.
Sims, L.D., Ellis, T.M., Liu, K.K., Dyrting, K., Wong, H., Peiris, M.,
Guan, Y. & Shortridge, K.F. (2003). Avian influenza in Hong Kong
1997 _/2002. Avian Diseases, 47 , 832 _/838.
Spackman, E., Senne, D.A., Myers, T.J., Bulaga, L.L., Garber, L.P.,
Perdue, M.L., Lohman, K., Daum, L.T. & Suarez, D.L. (2002).
Development of a real-time reverse transcriptase PCR assay for type
A influenza virus and the avian H5 and H7 hemagglutinin subtypes.
Journal of Clinical Microbiology, 40 , 3256 _/3260.
Swayne, D.E., Beck, J.R., Garcia, M. & Stone, H.D. (1999). Influence
of virus strain and vaccine mass on efficacy of H5 avian influenza
inactivated vaccines. Avian Pathology, 28, 245_/255.
Swayne, D.E., Garcia, M., Beck, J.R., Kinney, N. & Suarez, D.L.
(2000). Protection against diverse highly pathogenic avian influenza
viruses in chickens immunized with a recombinant fowl pox vaccine
containing an H5 avian influenza gene hemagglutinin gene insert.
Vaccine, 18 , 1088 _/1095.
Swayne, D.E., Beck, J.R., Perdue, M.L. & Beard, C.W. (2001). Efficacy
of vaccines in chickens against highly pathogenic Hong Kong H5N1
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Vaccination interrupts H5N1 virus transmission 411
- 25.09.2006, 13:03 #82
- 25.09.2006, 13:18 #83Steiof: Und noch eine Anmerkung: Es hat mich die letzten Monate immer mehr verwundert, wie hartnäckig das FLI auf Wildvögel verwiesen hat, egal wo, wie und wann das Virus aufgetreten ist. Mit wissenschaftlichen Denkmustern kann ich mir dies nicht mehr erklären. Es hat sich bei mir vielmehr zunehmend der Eindruck eingestellt, dass es um eine tatsächliche Aufklärung gar nicht mehr geht. Was sind die Gründe für diese einseitige Betrachtung? Spielt der Wunsch eine Rolle, Forschungsmittel zu aquirieren? Denn wenn es die Zugvögel sind, muss man natürlich weiter und weiter forschen (bisher meines Wissens übrigens ohne greifbare Ergebnisse). Wie unspektakulär, wenn man einfach nur feststellen würde, dass die Importe von Geflügel, Geflügelprodukten und dergleichen an den Außengrenzen der EU oder sogar an den nationalen Grenzen besser kontrolliert werden müssten! Gibt es vielleicht sogar wirtschaftliche Interessengruppen, die sich gegen derartige Feststellungen wehren? Wie skrupellos bei ungenügender Kontrolle sogar mit "unseren" Futtermitteln umgegangen wird, zeigt der jüngste Gammelfleischskandal - und auch BSE sollten wir nicht vergessen.
Noch ein Gedanke: Soll dieses ständige Zeigen auf die Wildvögel gar von Film ablenken? Denn noch immer hat kein Mensch eine plausible Idee, wie das Virus nach Rügen gekommen ist. Vielleicht werden wir erst in ein paar Jahren erfahren, was sich wirklich dort abgespielt hat. Vielleicht gelingt es auch einem unabhängigen Journalisten, eine etwas klarere Sicht der Dinge zu erhalten.
Aber wie kam es hier her?
Siehe erster Absatz.
- 25.09.2006, 13:34 #84Protection of chickens from lethal avian influenza A virus
infection by live-virus vaccination with infectious laryngotracheitis
virus recombinants expressing the hemagglutinin (H5 ) gene
Do¨ rte Lu¨schow a, Ortrud Werner b, Thomas C. Mettenleiter a, Walter Fuchs a,*
Received 6 February 2001; received in revised form 12 April 2001; accepted 12 April 2001
- 25.09.2006, 14:21 #85
Na, letzten August hieß es noch, dass dieser Impfstoff dieses Jahr marktreif wäre, dann war Funkstille. Dann gab es auf einmal den ND-basierten, ja und der braucht jetzt auch nochmal vier Jahre. Schon pfiffig, oder auch nicht ...
- 25.09.2006, 14:47 #86
- 25.09.2006, 15:11 #87
- 25.09.2006, 15:16 #88
Zum derzeitigen Stand der Vektorvirustechnologie im Bezug auf ND:
BIOSECURITY >> AGRICULTURAL BIOSECURITY >> NEWS >>
Recombinant vaccines protect poultry from avian flu, Newcastle disease
Jun 2, 2006 (CIDRAP News) – Two vaccines protected chickens against Newcastle disease (ND) and avian influenza and may provide approaches for producing human vaccines against the H5N1 avian flu virus, according to two studies published in the May 26 issue of the Proceedings of the National Academy of Sciences.
The new vaccines relied on recombinant methodology to create chimeric viruses containing portions of both ND and avian influenza virus (AIV) genomes. Recombinant viruses were employed as bivalent, live-virus vaccines to immunize chickens against avian influenza. Immunized chickens were later challenged for both diseases and also tested for viral shedding.
Both vaccines protected animals from ND and AIV. One vaccine also had the advantage of allowing serologic discrimination between vaccinated and field-infected birds, an important aid for controlling spread among poultry flocks. Because of concerns about potential recombination between the vaccine strain and native viruses, vaccinated chickens were also tested for recombinant viruses. Analysis did not reveal any evidence of vaccine-derived recombinant viruses or enhanced virulence.
Vaccine combines Newcastle, H5N2 viruses
Jutta Veits and colleagues cloned a full-length copy of a low-pathogenic ND strain and then inserted the coding sequence for the hemagglutinin of a highly pathogenic avian influenza virus (H5N2) between two ND virus genes. The resultant product was an ND virus that expressed the hemagglutinin H5 (HA) of avian influenza. The team synthetically modified this virus to enhance production of HA transcripts and protein and to minimize potential viral recombination.
Twenty-five 3-week old, pathogen-free chickens were immunized by oculonasal administration of the modified virus. Chickens tested 3 weeks after inoculation had ND- and AIV-specific antibodies and were also protected against clinical challenges with lethal doses of either virus, the report says. No AIV was shed from vaccinated chickens. Recombinant viruses isolated from chickens that had been inoculated with the vaccine at 1 day old were found to be benign rather than virulent.
Enhanced virulence and viral shedding from vaccinated animals, two concerns about recombinant vaccines, were eased by these findings, according to the article. Recombination events among vaccine and wild viruses may produce more virulent strains, and propagation of AIV among vaccinated birds might mask such events, making control more difficult. In addition, shedding of virus could promote spread of disease.
An important characteristic of this vaccine, the authors write, is that it allows serologic discrimination between vaccinated and wild virus–infected animals. Testing detected antibodies against the nucleoprotein of AIV. This antibody is absent in vaccinated chickens but present and identifiable in vaccinated chickens that are infected with AIV.
Such a vaccine would allow identification and culling of birds infected after vaccination. It thus circumvents the problem of undetected circulation of virus among vaccinated birds and represents a potentially important tool for controlling AIV. The authors state that this vaccine "is suitable as a bivalent vaccine against ND and AIV and may be used as a marker vaccine for the control of avian influenza."
Another recombinant approach
A second group of researchers used reverse genetics to produce vaccines for negative-stranded RNA viruses that also protected chickens against a highly pathogenic AIV (H5N1) and a highly virulent ND. Man-Seong Park and colleagues constructed an AIV vaccine that substituted the "a" portion of the hemagglutinin-neuraminidase gene of ND for the neuraminidase protein gene of the H5N1 avian influenza virus as one approach. These constructs were used to test modified viral sequences aimed at reducing potential spontaneous conversion to virulence and for making an effective bivalent vaccine.
The resultant bivalent vaccine (rNDV/F3aa-chimeric H7) was based on expression of part of H7 AIV hemagglutinin in a truncated and attenuated ND background. The chimeric virus enhanced the incorporation of the foreign protein into virus particles and reduced concerns about the other vaccine's potential for spontaneous conversion to virulence.
Twenty white Leghorn chickens were vaccinated with the bivalent vaccine by eyedrop application, with half receiving one dose and half getting two doses. Vaccinated chickens were challenged with both diseases. A single immunization induced 90% protection against H7N7, a highly pathogenic AIV strain, and complete immunity against a highly virulent ND virus.
The authors suggest that chimeric constructs might serve as the basis for developing convenient, affordable, and effective vaccination against these diseases in chickens and other poultry. A similar approach might also be used to produce human viral vaccines, provided suitable viral vectors can be found for humans. Humans are not susceptible to Newcastle disease, so developing such a vaccine would hinge on using a virus that easily infects people to get a safe and effective immune system response.
Veits J, Wiesner D, Fuchs W, et al. Newcastle disease virus expressing H5 hemagglutinin gene protects chickens against Newcastle disease and avian influenza. Proc Natl Acad Sci 2006 May 23;103(21):8197-202 [Abstract]
Park MS, Steel J, Garcia-Sastre A, et al. Engineered viral vaccine constructs with dual specificity: avian influenza and Newcastle disease. Proc Natl Acad Sci 2006 May 23;103(21):8203-8
Media source: Center for Infectious Disease Research & Policy
Academic Health Center -- University of Minnesota
- Herbstvogelzug und Verschärfung der StallpflichtRegistrieren bzw. einloggen, um diese und auch andere Anzeigen zu deaktivieren
- 25.09.2006, 15:52 #89
- 25.09.2006, 16:16 #90
Bitte nicht aus dem Kontext pflücken, man nimmt doch gerne was zum Schmunzeln als Einleitung.
In Hongkong witzelt man über den Zufall, dass der räumlich völlig isolierte Ausbruch auf Rügen nur wenige Kilometer neben den Laboren des Friedlich-Löffler-Institut stattgefunden hat (Quelle3a). Wurde dort mit dem Erreger gearbeitet und haben sich alle mit dem Erreger umgehenden Mitarbeiter ausreichend dekontaminiert, bevor sie das Institutsgelände verlassen haben? Für wesentlich wahrscheinlicher halte ich aber den Weg über Dünger. Hierauf weisen die hauptsächlich betroffenen Wasservögel hin. Ich habe nirgends gelesen oder gehört, dass Kontrollen der ausgebrachten Dünger vorgenommen wurden und dieser Infektionsweg ausgeschlossen werden kann. Hier müsste intensiv gefahndet werden, denn wenn Geschäfte zu machen sind, sind auch Falschdeklarationen nicht auszuschließen (siehe „Gammelfleisch-„ und BSE-Skandal, illegaler Handel mit geschützten Tier- und Pflanzenarten).