Domestic Waterfowl Research Articles

Single Vaccination Provides Limited Protection to Ducks and Geese Against H5N1 High Pathogenicity Avian Influenza Virus

Since 2002, high pathogenicity avian influenza (HPAI) has spread from Asia to Europe and into Africa, causing the largest epizootic of HPAI of the last 50 yr, including infecting domestic and wild waterfowl. Our study was conducted to investigate whether a single vaccination of 7-day-old domestic ducks and geese with inactivated oil emulsion vaccines resulted in protection against HPAI virus challenge at 30 days of age. In ducks, some but not all vaccines decreased oropharyngeal and cloacal viral shedding for different periods postchallenge when compared with the sham group. In geese, decreased morbidity signs and mortality were noted but limited to some vaccines. Best protection was seen with a vaccine homologous to HPAI challenge virus. Limited decreases in oropharyngeal and cloacal viral shedding and mixed results were attained when looking at seroconversion. Our results indicate a single dose of oil-emulsified vaccine optimized for chickens did not provide adequate protection for ducks and geese against HPAI virus, and, at a minimum, additional research is needed to formulate waterfowl-specific vaccines.

Production, purification and characterization of polyclonal antibody against the truncated gK of the duck enteritis virus

Duck virus enteritis (DVE) is an acute, contagious herpesvirus infection of ducks, geese, and swans, which has produced significant economic losses in domestic and wild waterfowl. With the purpose of decreasing economic losses in the commercial duck industry, studying the unknown glycoprotein K (gK) of DEV may be a new method for preferably preventing and curing this disease. So this is the first time to product and purify the rabbit anti-tgK polyclonal antibody. Through the western blot and ELISA assay, the truncated glycoprotein K (tgK) has good antigenicity, also the antibody possesses high specificity and affinity. Meanwhile the rabbit anti-tgK polyclonal antibody has the potential to produce subunit vaccines and the functions of neutralizing DEV and anti-DEV infection because of its neutralization titer. Indirect immunofluorescent microscopy using the purified rabbit anti-tgK polyclonal antibody as diagnostic antibody was susceptive to detect a small quantity of antigen in tissues or cells. This approach also provides effective experimental technology for epidemiological investigation and retrospective diagnose of the preservative paraffin blocks.

Expressing gK gene of duck enteritis virus guided by bioinformatics and its applied prospect in diagnosis

BackgroundDuck viral enteritis, which is caused by duck enteritis virus (DEV), causes significant economic losses in domestic and wild waterfowls because of the high mortality and low egg production rates. With the purpose of eliminating this disease and decreasing economic loss in the commercial duck industry, researching on glycoprotein K (gK) of DEV may be a new kind of method for preventing and curing this disease. Because glycoproteins project from the virus envelope as spikes and are directly involved in the host immune system and elicitation of the host immune responses, and also play an important role in mediating infection of target cells, the entry into cell for free virus and the maturation or egress of virus. The gK is one of the major envelope glycoproteins of DEV. However, little information correlated with gK is known, such as antigenic and functional characterization.ResultsBioinformatic predictions revealed that the expression of the full-length gK gene (fgK) in a prokaryotic system is difficult because of the presence of suboptimal exon and transmembrane domains at the C-terminal. In this study, we found that the fgK gene might not be expressed in a prokaryotic system in accordance with the bioinformatic predictions. Further, we successfully used bioinformatics tools to guide the prokaryotic expression of the gK gene by designing a novel truncated gK gene (tgK). These findings indicated that bioinformatics provides theoretical data for target gene expression and saves time for our research. The recombinant tgK protein (tgK) was expressed and purified by immobilized metal affinity chromatography (IMAC). Western blotting and indirect enzyme-linked immunosorbent assay (ELISA) showed that the tgK possessed antigenic characteristics similar to native DEV-gK.ConclusionsIn this work, the DEV-tgK was expressed successfully in prokaryotic system for the first time, which will provide usefull information for prokaryotic expression of alphaherpesvirus gK homologs, and the recombinant truncated gK possessed antigenic characteristics similar to native DEV gK. Because of the good reactionogenicity, specificity and sensitivity, the purified tgK could be useful for developing a sensitive serum diagnostic kit to monitor DEV outbreaks.

Summary of Avian Influenza Activity in Europe, Asia, and Africa, 2006–2009

Events during the period extending from 2006 to 2009 have been overshadowed by the ongoing panzootic with H5N1 (highly pathogenic notifiable avian influenza [HPNAI]), which has afflicted 63 countries and three continents (Africa, Asia, and Europe) during the review period. Two countries, Indonesia and Egypt, have formally declared the disease endemic to the World Organisation for Animal Health, while others have used a variety of approaches aimed at containment, control, and eradication. These approaches have achieved variable success, but in 2009 several countries that had previously declared themselves free of HPNAI became reinfected. In addition, the virus continued to be detected widely in wild bird populations, even in the absence of local poultry outbreaks. Other poultry outbreaks with HPNAI have been reported in South Africa (in ostriches with H5N2 in 2006) and the U.K. (in chickens with H7N7 in 2008). Also notable was the report of H5N2 HPNAI in wild bird populations in North Africa in 2007. Improved active surveillance systems and vigilance for notifiable avian influenza (NAI) in domestic poultry, especially in host groupings, in which clinical signs following infection may be inapparent (e.g., domestic waterfowl), have inevitably resulted in the detection and reporting of other activity. Low pathogenicity NAI H5 or H7 viruses were isolated/detected from poultry in Belgium (H5N2, 2008), Chinese Taipei (H5N2, 2008), Denmark (H5N2, 2006; H7N1, 2008), France (H5N2, 2007), Germany (H7N3, 2008), Italy (H7N7, 2006; H7N3, 2007-08), the Netherlands (H7N7, 2006), Portugal (H5N2, 2007; H5N3, 2007), the Republic of Korea (H7N8, 2007; H5N2, 2008), and the U.K. (H7N3, 2006; H7N2, 2007). In addition, there has also been significant activity with H6 and H9 viruses in poultry populations, especially in Asia.

Spatial transmission of avian influenza (type H5) in birds

Highly pathogenic avian influenza (HPAI) H5N1 continues to threaten domestic and wild birds, as well as human health. However, the mechanism of spatial transmission of HPAI is still unclear. We analyzed the current distribution of HPAI occurrences based on World Organization for Animal Health reported data from 3049 sites in the world from December 2003 to June 2006, and found that these sites were spaced at distances with a frequency peak of 100-200 km. We built a cellular automata model to simulate the spatial transmission process of HPAI as a function of transmission distance, variance of the transmission distance, infection rate, and transmission times (how many times HPAI transmits from one host to another before suppression). We determined that the transmission distance between HPAI occurrences is approximately 100 km on the basis of historical HPAI occurrences from 2003 to 2006 in both wild and domestic birds. To effectively reduce the long-distance spreading of HPAI, preventing close contact between domestic birds and waterfowl within a radius of 100 km around HPAI occurrence sites is essential.

Surveillance for avirulent Newcastle disease viruses in domestic ducks (Anas platyrhynchos and Cairina moschata) at live bird markets in Eastern China and characterization of the viruses isolated

We isolated and identified 201 Newcastle disease viruses (NDVs) from domestic ducks in a 5-year surveillance study at live bird markets in Eastern China. Seventy-three of these isolates were characterized biologically and genetically. Fusion protein (F) genes of these isolates were amplified by reverse transcription-polymerase chain reaction and sequenced. Intracerebral pathogenicity index tests in 1-day-old specific-pathogen-free chickens and the mean death time of embryonated fowl eggs in addition to the cleavage site analysis of the F-protein precursor for these viruses showed that they were all avirulent NDVs. Phylogenetic analysis based on partial sequences of the F gene showed that 30 isolates clustered into the class I clade and the other 43 isolates clustered into genotype I of class II, but diverged from the vaccine virus Queensland V4, which is extensively used in China. Most class I viruses (18/30) formed a separate branch closest to the Hong Kong live bird market strains that have been recently designated as genotype 3, while the rest (12/30) were closely related to some European viruses within genotype 2. All of the 43 class II genotype I viruses diverged from viruses originally assigned to genotype Ia and formed a separate sublineage designated as Ib with water bird isolates from the Far East, suggesting the possible transmission between the wild and domestic waterfowl. The results in the present study clearly showed that the domestic duck population carries avirulent NDVs with genetic divergence regularly and may act as one of the important reservoirs.

Sequence diversity of the haemagglutinin open reading frame of recent highly pathogenic avian influenza H5N1 isolates from Egypt

The sequences encoding the haemagglutinin (HA) of twelve H5N1 isolates obtained in 2006 and 2007 from different avian species in backyard holdings and poultry farms in Egypt revealed amino acid variations across the polypeptide and also in the polybasic cleavage motif of three of the isolates from backyard poultry with one, so far, unique mutation in an isolate from a chicken. The HAs of two isolates (A/goose/Egypt/R4/2007, A/chicken/Egypt/R3/2007) collected on the same day in the same village from two neighbouring houses were found to differ from each other. Five out of the seven nucleotide exchanges in these two isolates were translationally silent, and two resulted in amino acid substitutions: one in the polybasic cleavage motif and the other in the signal peptide. Circulation of different H5N1 strains possessing considerable variations in backyard poultry, particularly domestic waterfowl, draws attention to the evolution of H5N1 subtypes in Egypt.

Genetic analysis of avian influenza A viruses isolated from domestic waterfowl in live-bird markets of Hanoi, Vietnam, preceding fatal H5N1 human infections in 2004

The first known cases of human infection with highly pathogenic avian influenza (HPAI) H5N1 viruses in Vietnam occurred in late 2003. However, HPAI H5N1 and low-pathogenic avian influenza (LPAI) H5N2 and H9N3 viruses were isolated from domestic waterfowl during live-bird market (LBM) surveillance in Vietnam in 2001 and 2003. To understand the possible role of these early viruses in the genesis of H5N1 strains infecting people, we performed sequencing and molecular characterization. Phylogenetic analysis revealed that the hemagglutinin (HA) genes of two geese HPAI H5N1 strains belonged to clade 3, and their surface glycoprotein and replication complex genes were most closely related (98.5-99.7% homologous) to A/duck/Guangxi/22/01 (H5N1) virus, detected contemporarily in southern China, whilst the M and NS genes were derived from an A/duck/Hong Kong/2986.1/00 (H5N1)-like virus. The H5 HA gene of the duck HPAI H5N1 strain belonged to clade 5 and acquired a gene constellation from A/quail/Shantou/3846/02 (H5N1), A/teal/China/2978.1/02 (H5N1) and A/partridge/Shantou/2286/03 (H5N1)-like viruses. The phylogenetic analysis further indicated that all eight gene segments of goose and duck HPAI H5N1 and LPAI H5N2 viruses were distinct from those of H5N1 clade-1 viruses known to have caused fatal human infections in Vietnam since late 2003. The duck H9N3 isolates derived genes from aquatic-bird influenza viruses, and their H9 HA belonged to the Korean lineage. The PB2 gene of A/duck/Vietnam/340/01 (H9N3) virus had lysine at position 627. Based on the molecular characterization of specific amino acid residues in the surface and relevant internal protein-coding genes, the Vietnamese H5N1 and H9N3 virus isolates indicated specificity to avian cell surface receptor and susceptibility for currently licensed anti-influenza A virus chemotherapeutics. Our findings suggest that the H5N1 and H5N2 viruses that circulated among geese and ducks in LBMs in Hanoi, Vietnam, during 2001 and 2003 were not the immediate ancestors of the clade-1 viruses associated with fatal human infections in Vietnam. The clade-1 HPAI H5N1 viruses were independently introduced into Vietnam.

Four different sublineages of highly pathogenic avian influenza H5N1 introduced in Hungary in 2006–2007

Highly pathogenic avian influenza (HPAI) H5N1 viruses were introduced to Hungary during 2006–2007 in three separate waves. This study aimed at determining the full-length genomic coding regions of the index strains from these epizootics in order to: (i) understand the phylogenetic relationship to other European H5N1 isolates, (ii) elucidate the possible connection between the different outbreaks and (iii) determine the putative origin and way of introduction of the different virus variants. Molecular analysis of the HA gene of Hungarian HPAI isolates obtained from wild birds during the first introduction revealed two groups designated Hungarian1 (HUN1) and Hungarian2 (HUN2) within sublineage 2.2B and clade 2.2.1, respectively. Sequencing the whole coding region of the two index viruses A/mute swan/Hungary/3472/2006 and A/mute swan/4571/Hungary/2006 suggests the role of wild birds in the introduction of HUN1 and HUN2 viruses: the most similar isolates to HUN1 and HUN2 group were found in wild avian species in Croatia and Slovakia, respectively. The second introduction of HPAI H5N1 led to the largest epizootic in domestic waterfowl in Europe. The index strain of the epizootic A/goose/Hungary/14756/2006 clustered to sublineage 2.2.A1 forming the Hungarian3 (HUN3) group. A common ancestry of HUN3 isolates with Bavarian strains is suggested as the most likely scenario of origin. Hungarian4 (HUN4) viruses isolated from the third introduction clustered with isolate A/turkey/United Kingdom/750/2007 forming a sublineage 2.2.A2. The origin and way of introduction of HUN4 viruses is still obscure, thus further genetic, phylogenetic, ecological and epidemiological data are required in order to elucidate it.

Efficacy of a commercial inactivated H5 influenza vaccine against highly pathogenic avian influenza H5N1 in waterfowl evaluated under field conditions

Highly pathogenic avian influenza virus (HPAIV) can cause devastating losses in the poultry industry. In addition, several HPAIV exhibit a zooanthroponotic potential and can cause fatal infections in humans. These attributes particularly apply to HPAIV H5N1 of Asian origin. Due to the absence of overt clinical symptoms, introduction and subsequent spread of HPAIV H5N1 in domestic waterfowl (especially ducks) may occur undetected, which increases the risk of transspecies transmissions to highly vulnerable gallinaceous poultry and mammals, including humans. Humans may also become infected with HPAIV H5N1 by food products from slaughtered, silently infected ducks. Vaccination against HPAIV can raise a protective barrier against an incursion of HPAIV since, at least under experimental conditions, the reproduction factor R0 lowered to <1, which ensures eradication of the virus. The objective of this study was to analyse whether these results can also be obtained under free-ranging field conditions in commercially reared flocks of goose parents and fattening ducks injected with a licensed, adjuvanted inactivated H5N2 vaccine. The time and labour required for the vaccination of these geese and duck flocks exceeded expected values, mainly due to animal sorting according to foot ring labels. No adverse effects directly associated with vaccination were observed. Serologically, a homogenous H5-specific antibody response was induced. Titres varied with temporal distance from the last application of vaccine. Geese parents were clinically protected against challenge with HPAIV A/Cygnus cygnus/Germany/R65/06 (H5N1), but still could be infected and spread HPAIV H5N1, albeit at lower levels and for shorter periods compared to unvaccinated controls. Fattening Pekin ducks proved to be clinically resistant against challenge virus infection and shed very little virus.

Pathogenesis and pathobiology of avian influenza virus infection in birds

Avian influenza (AI) viruses vary in their ability to produce infection, disease and death in different bird species. Based on the pathobiological effect in chickens, AI viruses (AIV) are categorised as low pathogenic (LPAIV) or highly pathogenic (HPAIV). Typically, LPAIV cause asymptomatic infections in wild aquatic birds, but when introduced into domesticated poultry, infections may be asymptomatic or produce clinical signs and lesions reflecting pathophysiological damage to the respiratory, digestive and reproductive systems. The HPAIV have primarily been seen in gallinaceous poultry, producing high morbidity and mortality, and systemic disease with necrosis and inflammation in multiple visceral organs, nervous and cardiovascular systems, and the integument. Although HPAIV have rarely infected domestic waterfowl or wild birds, the Eurasian-African H5N1 HPAIV have evolved over the past decade with the unique capacity to infect and cause disease in domestic ducks and wild birds, producing a range of syndromes including asymptomatic respiratory and digestive tract infections; systemic disease limited to two or three critical organs, usually the brain, heart and pancreas; and severe disseminated infection and death as seen in gallinaceous poultry. Although experimental studies using intranasal inoculation have produced infection in a variety of wild bird species, the inefficiency of contact transmission in some of them, for example, passerines and Columbiformes, suggests they are unlikely to be a reservoir for the viruses, while others such as some wild Anseriformes, can be severely affected and could serve as a dissemination host over intermediate distances.

Risk factors and characteristics of H5N1 Highly Pathogenic Avian Influenza (HPAI) post-vaccination outbreaks

Highly pathogenic avian influenza (HPAI) virus H5N1 is now endemic in South-East Asia but HPAI control methods differ between countries. A widespread HPAI vaccination campaign that started at the end of 2005 in Viet Nam resulted in the cessation of poultry and human cases, but in 2006/2007 severe HPAI outbreaks re-emerged. In this study we investigated the pattern of this first post-vaccination epidemic in southern Viet Nam identifying a spatio-temporal cluster of outbreak occurrence and estimating spatially smoothed incidence rates of HPAI. Spatial risk factors associated with HPAI occurrence were identified. Medium-level poultry density resulted in an increased outbreak risk (Odds ratio (OR) = 5.4, 95% confidence interval (CI): 1.6–18.9) but also climate-vegetation factors played an important role: medium-level normalised difference vegetation indices during the rainy season from May to October were associated with higher risk of HPAI outbreaks (OR = 3.7, 95% CI: 1.7–8.1), probably because temporal flooding might have provided suitable conditions for the re-emergence of HPAI by expanding the virus distribution in the environment and by enlarging areas of possible contacts between domestic waterfowl and wild birds. On the other hand, several agricultural production factors, such as sweet potatoes yield, increased buffalo density, as well as increased electricity supply were associated with decreased risk of HPAI outbreaks. This illustrates that preventive control measures for HPAI should include a promotion of low-risk agricultural management practices as well as improvement of the infrastructure in village households. Improved HPAI vaccination efforts and coverage should focus on medium poultry density areas and on the pre-monsoon time period.

Serologic Survey of Birds for West Nile Flavivirus in Southern Moravia (Czech Republic)

A serosurvey for West Nile virus (WNV) was carried out in 54 domestic birds (geese and ducks bred on fishponds) and 391 wild birds representing 28 migratory and resident species, using a plaque-reduction neutralization microtest with Vero cells and Egyptian topotype Eg-101 strain as test virus. The birds were sampled in the South-Moravian fishpond ecosystem between 2004 and 2006. Antibodies to WNV were not detected in domestic waterfowl, but 23 (5.9%) free-living birds of 10 species showed a positive response. These were the common coot (Fulica atra, 5 positive/18 examined), common kingfisher (Alcedo atthis, 1/1), reed warbler (Acrocephalus scirpaceus, 2/80), sedge warbler (A. schoenobaenus, 3/80), marsh warbler (A. palustris, 2/28), Savi's warbler (Locustella luscinioides, 3/12), reed bunting (Emberiza schoeniclus, 1/28), blackcap (Sylvia atricapilla, 2/11), penduline tit (Remiz pendulinus, 1/14), blue tit (Parus caeruleus, 1/1), and starling (Sturnus vulgaris, 2/4). The antibody titers were comparatively low (1:20-1:40), and the only high titer (1:160) was found in an adult marsh warbler. When 14 of the sera reacting with WNV were titrated in parallel with Usutu Flavivirus, 12 were interpreted as having specific antibodies to WNV, one coot had a higher titer against Usutu virus, and another one could not be attributed to either of the two viruses. In conclusion, 13 (3.3%) of 391 wild birds had specific antibodies to WNV. The results indicate that WNV activity in southern Moravia was limited during 2004-2006.

Wild Birds and Avian Influenza

In Japan, Highly Pathogenic Avian Influenza virus prevalence had not occurred from 1925 to January 2004. From this fact, residental birds in Japan are not expected to have the virus. Infection is mediated by wild birds from Korea or China – the areas Highly Pathogenic Avian Influenza prevalence occurred recently – to domestic waterfowl.

The fight against new types of influenza virus

In 1997, during an outbreak in chickens in Hong Kong the avian H5N1 influenza virus crossed the species barrier and infected 18 people, of which 6 cases were fatal. The virus also infected wild birds and continued to circulate and mutate in geese and ducks in southeastern China. Since this occurrence, new antigenic variants that are highly pathogenic for humans as well as wild, domestic, and exotic waterfowl continue to appear in Hong Kong. This virus is spreading across Asia, and is encroaching upon Europe and other continents. Wild birds are now considered as the main reservoir of H5N1 virus. Humans become infected with this H5N1 virus usually via close contact with infected birds or a highly contaminated environment. The very low transmissibility of this virus prevented further person-to-person dissemination in spite of the complete absence of immunity in the human population to H5N1 viruses. Viruses of the H5N1 subtype are characterized by an exceptionally high pathogenicity for humans. The cause of the viral virulence is not known so far; however, several virulence factors are considered. The unprecedented capability of H5N1 viruses to kill humans intensifies the concern about its pandemic potential with catastrophic consequences. The effectiveness of existing antivirals as well as vaccines for humans and birds are reviewed.

Principles for Vaccine Protection in Chickens and Domestic Waterfowl against Avian Influenza

The H5N1 highly pathogenic (HP) avian influenza (AI) epizootic began with reports of mortality from China in 1996 and, by June 2005, caused outbreaks of disease in nine additional Asian countries, affecting or resulting in culling of over 200 million birds. Vaccines can be used in programs to prevent, manage, or eradicate AI. However, vaccines should only be used as part of a comprehensive control strategy that also includes biosecurity, quarantine, surveillance and diagnostics, education, and elimination of infected poultry. Potent AI vaccines, when properly used, can prevent disease and death, increase resistance to infection, reduce field virus replication and shedding, and reduce virus transmission, but do not provide "sterilizing immunity" in the field; i.e., vaccination does not completely prevent AI virus replication. Inactivated AI vaccines and a recombinant fowlpox-H5-AI vaccine are licensed and used in various countries. Vaccines have been shown to protect chickens, geese, and ducks from H5 HPAI. The inactivated vaccines prevented disease and mortality in chickens and geese, and reduced the ability of the field virus to replicate in gastrointestinal and respiratory tracts. Although the Asian H5N1 HPAI virus did not cause disease or mortality in ducks, the use of inactivated vaccine did reduce field virus replication in the respiratory and intestinal tracts. The inactivated vaccine protected geese from morbidity and mortality, and reduced challenge virus replication. The recombinant fowlpox-H5-AI vaccine has provided similar protection, but the vaccine is used only in chickens and with the advantage of application at 1 day of age in the hatchery.

Birds and Influenza H5N1 Virus Movement to and within North America

Highly pathogenic avian influenza (HPAI) H5N1 expanded considerably during 2005 and early 2006 in both avian host species and geographic distribution. Domestic waterfowl and migratory birds are reservoirs, but lethality of this subtype appeared to initially limit migrant effectiveness as introductory hosts. This situation may have changed, as HPAI H5N1 has recently expanded across Eurasia and into Europe and Africa. Birds could introduce HPAI H5N1 to the Western Hemisphere through migration, vagrancy, and importation by people. Vagrants and migratory birds are not likely interhemispheric introductory hosts; import of infected domestic or pet birds is more probable. If reassortment or mutation were to produce a virus adapted for rapid transmission among humans, birds would be unlikely introductory hosts because of differences in viral transmission mechanisms among major host groups (i.e., gastrointestinal for birds, respiratory for humans). Another possible result of reassortment would be a less lethal form of avian influenza, more readily spread by birds.

History and Evolution of HPAI Viruses in Southeast Asia

Highly pathogenic avian influenza (HPAI) has been recognized as a serious viral disease of poultry since 1878. The number of outbreaks of this disease globally has increased in the past 10 years culminating in 2004 with the unprecedented outbreak of H5N1 HPAI involving nine countries in East and South East Asia. Apart from the geographical extent of this outbreak and apparent rapid spread, this epidemic has a number of unique features, among which is the carriage of highly pathogenic AI viruses by asymptomatic domestic waterfowl. When this disease first emerged it was recognized almost simultaneously in a number of countries for the first time. This created considerable concern among both veterinary and public health authorities especially as the virus was also shown to cause fatal disease in humans. This article brings together a range of information on H5N1 HPAI viruses in Asia that were collected by FAO during the past year through field projects and explores possible reasons for the emergence of the disease in late 2003 and early 2004. Key epidemiological features of the disease in different Asian countries are described in an attempt to look for, and where possible, explain similarities and differences. This includes assessment of factors that could have contributed to the spread of the disease. Molecular aspects of the viruses are examined to assess relationships between isolates from different locations and times so as to gain insights into the origins of viruses in various countries. It is apparent that the coincidence and grouping of the reports declaring the outbreaks of HPAI did not truly reflect the time course of disease emergence, which was widespread well before the outbreak. The factors that could have led to a change from infection to emergence of widespread disease in 2003-2004 are discussed. There are still some questions that remain unanswered regarding the origins of the 2004 outbreak. This article does not provide answers to all of these, but brings together what is currently known about these outbreaks and the viruses that have caused them.

Protective efficacy in chickens, geese and ducks of an H5N1-inactivated vaccine developed by reverse genetics

We generated a high-growth H5N1/PR8 virus by plasmid-based reverse genetics. The virulence associated multiple basic amino acids of the HA gene were removed, and the resulting virus is attenuated for chickens and chicken eggs. A formalin-inactivated oil-emulsion vaccine was prepared from this virus. When SPF chickens were inoculated with 0.3 ml of the vaccine, the hemagglutinin-inhibition (HI) antibody became detectable at 1 week post-vaccination (p.v.) and reached a peak of 10log2 at 6 weeks p.v. then slowly declined to 4log2 at 43 weeks p.v. Challenge studies performed at 2, 3 and 43 weeks p.v. indicated that all of the chickens were completely protected from disease signs and death. Ducks and geese were completely protected from highly pathogenic H5N1 virus challenge 3 weeks p.v. The duration of protective immunity in ducks and geese was investigated by detecting the HI antibody of the field vaccinated birds, and the results indicated that 3 doses of the vaccine inoculation in geese could induce a 34 weeks protection, while 2 doses induced more than 52 weeks protection in ducks. We first reported that an oil-emulsion inactivated vaccine derived from a high-growth H5N1 vaccine induced approximately 10 months of protective immunity in chickens and demonstrated that the oil-emulsion inactivated avian influenza vaccine is immunogenic for geese and ducks. These results provide useful information for the application of vaccines to the control of H5N1 avian influenza in poultry, including chickens and domestic waterfowl.

Origin and evolution of highly pathogenic H5N1 avian influenza in Asia

Outbreaks of highly pathogenic avian influenza caused by H5N1 viruses were reported almost simultaneously in eight neighbouring Asian countries between December 2003 and January 2004, with a ninth reporting in...