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1.
On 19th July 2007 re-occurrence of the H5N1 highly pathogenic avian influenza (HPAI) virus was noticed in Europe. The index strain of this novel H5N1 lineage was identified in the Czech Republic where it caused historically the first HPAI outbreak in commercial poultry. In the present study we performed molecular and phylogenetic analysis of the index strain of the re-emerging H5N1 virus lineage along with the Czech and the Slovak H5N1 strains collected in 2006 and established the evolutionary relationships to additional viruses circulated in Europe in 2005-2006. Our analysis revealed that the Czech and the Slovak H5N1 viruses collected during 2006 were separated into two sub-clades 2.2.1 and 2.2.2, which predominated in Europe during 2005-2006. On the contrary the newly emerged H5N1 viruses belonged to a clearly distinguishable sub-clade 2.2.3. Within the sub-clade 2.2.3 the Czech H5N1 strains showed the closest relationships to the simultaneously circulated viruses from Germany, Romania and Russia (Krasnodar) in 2007 and were further clustered with the viruses from Afghanistan and Mongolia circulated in 2006. The origin of the Czech 2007 H5N1 HPAI strains was also discussed.  相似文献   

2.
Highly pathogenic avian influenza (HPAI) H5N1 virus is causing the death of a large number of wild birds and poultry. HPAI H5N1 was reported in the north of Iran in 2011. In this study, two A/Chicken/Iran/271/2011 and A/Duck/Iran/178/2011 viruses were genetically characterized by sequence analysis of Hemagglutinin (HA) and Neuraminidase (NA) genes. Phylogenetic analysis revealed that these viruses were different from previous Iranian isolates (Clade 2.2) and belonged to the subclade 2.3.2.1. The results showed that the detected viruses are almost identical to each other and closely related to HPAI H5N1 strains isolated in Mongolia in 2010. Based on the amino acid sequence analysis, these viruses at their HA cleavage sites contained the multibasic amino acid motif PQRERRRK-R/GLF lacking a lysine residue compared with the previous reports of the same motif. There is also a 20-amino acid deletion (resides 49–69) in the NA stalk similar to other viruses isolated after 2000. It seems that introduction of HPAI H5N1 to Iran might have happened by wild birds from Mongolian origin virus.  相似文献   

3.
As well as H5 highly pathogenic avian influenza viruses (HPAIV), H7 HPAIV strains have caused serious damages in poultry industries worldwide. Cases of bird-to-human transmission of H7 HPAIV have also been reported [11]. On the outbreak of avian influenza, rapid diagnosis is critical not only for the control of HPAI but also for human health. In the present study, a rapid diagnosis kit based on immunochromatography for the detection of H7 hemagglutinin (HA) antigen of influenza A virus was developed using 2 monoclonal antibodies that recognize different epitopes on the H7 HAs. The kit detected each of the tested 15 H7 influenza virus strains and did not react with influenza A viruses of the other subtypes than H7 or other avian viral and bacterial pathogens. The kit detected H7 HA antigen in the swabs and tissue homogenates of the chickens experimentally infected with HPAIV strain A/chicken/Netherlands/2586/03 (H7N7). The results indicate that the present kit is specific and sensitive enough for the diagnosis of HPAI caused by H7 viruses, thus, recommended for the field application as a pen-site test kit.  相似文献   

4.
In order to determine the actual prevalence of avian influenza viruses (AIV) in wild birds in the Czech Republic extensive surveillance was carried out between January and April 2006. A total of 2101 samples representing 61 bird species were examined for the presence of influenza A by using PCR, sequencing and cultivation on chicken embryos. AIV subtype H5N1 was detected in 12 Mute swans (Cygnus olor). The viruses were determined as HPAI (highly pathogenic avian influenza) and the hemagglutinin sequence was closely similar to A/mallard/Italy/835/06 and A/turkey/Turkey/1194/05. Following the first H5N1 case, about 300 wild birds representing 33 species were collected from the outbreak region and tested for the presence of AIV without any positive result. This is the first report of highly pathogenic avian influenza subtype H5N1 in the Czech Republic. The potential role of swan as an effective vector of avian influenza virus is also discussed.  相似文献   

5.
2021年1月12—19日,山东黄河三角洲国家级自然保护区大汶流管理站出现35只死亡的野生疣鼻天鹅。经现场调查,市级和省级实验室检测,诊断为疑似H5N8亚型高致病性禽流感,经国家禽流感参考实验室进行病毒分离鉴定,最终确定为H5N8亚型高致病性禽流感疫情。疫情发生后,通过现场调查、座谈及实验室检测等方式,对此次疫情开展了紧急流行病学调查,追溯疫情的可能来源,分析疫情的扩散风险,继而提出针对性的应急处置措施。调查发现,此次疫情由迁徙候鸟带毒引入引起的可能性较大;野生鸟类未及时开展免疫,导致体内抗体水平低下是疫情暴发的内源因素。由于迅速采取了合理的应急处理措施,此次疫情得到迅速控制,避免了疫情扩散。本次疫情警示,必须切实做好禽流感的强制免疫和监测工作,高度重视自然保护区及其附近场所珍稀禽类的免疫,以降低疫情发生风险。  相似文献   

6.
Characterization of an H5N1 avian influenza virus from Taiwan   总被引：1，自引：0，他引：1  
In 2003, an avian influenza (AI) virus of H5N1 subtype (A/Duck/China/E319-2/03; Dk/CHN/E319-2/03) was isolated from a smuggled duck in Kinmen Island of Taiwan. Phylogenetic analysis and pairwise comparison of nucleotide and amino acid sequences revealed that the virus displayed high similarity to the H5N1 viruses circulating in Asia during 2004 and 2005. The hemagglutinin (HA) protein of the virus contained multiple basic amino acid residues (-RERRRKR-) adjacent to the cleavage site between the HA1 and HA2 domains, showing the highly pathogenic (HP) characteristics. The HP phenotype was confirmed by experimental infection of chickens, which led up to 100% mortality within 24-72h postinfection. The virus replicated equally well in the majority of organs of the infected chickens with titers ranging from 10(7.5) to 10(4.7) 50% embryo lethal dose (ELD50) per gram of tissue. In a mouse model the virus exhibits low pathogenic characteristics with a lethal infection observed only after applying high inoculating dose (>or=10(7.6) ELD50) of the virus. The infectious virus particles were recovered only from the pulmonary system including trachea and lungs. Our study suggests that ducks infected with H5N1 AIV of HPAI pathotype showing no disease signs can carry the virus silently and that bird smuggling represent a serious risk for H5N1 HPAI transmission.  相似文献   

7.
In an intensive ostrich farming area in South Africa with a history of ostrich influenza outbreaks, we conducted a survey of avian influenza virus (AIV) and Newcastle disease virus (NDV) in wild aquatic birds. During late autumn and winter 1998, the time of year when outbreaks in ostriches typically start to occur, 262 aquatic birds comprising 14 species were sampled and tested for both virus infections. From eight samples, AIV, serotype H10N9, could be isolated. All isolates were apathogenic as determined by the intravenous pathogenicity index (0.00). Conversely, none of 33 sera of these wild birds showed antibodies against H10. However, one bird was found serologically positive for H6 AIV. This AIV serotype was later isolated from ostriches during an avian influenza outbreak in this area. No NDV was isolated although 34 of 46 serum samples contained NDV-specific antibodies. This is the first H10N9 isolate to be reported from Africa. In addition, our data support the notion that wild aquatic birds may function as a reservoir for AIV and NDV in South Africa.  相似文献   

8.
During the outbreak of highly pathogenic avian influenza (HPAI) H5N1 in Sweden in 2006, disease and mortality were observed in a number of wild bird species. Encephalitis was one of the most consistent and severe findings in birds submitted for postmortem examination. However, the distribution and severity of the inflammation varied among individuals. This study characterized the encephalitis and the phenotype of the cellular infiltrate in brains of 40 birds of various species naturally infected with HPAI H5N1. Brain sections stained with hematoxylin and eosin and immunostained for influenza A viral antigen were evaluated in parallel to brain sections immunostained with antibodies against T lymphocytes (CD3+), B lymphocytes (CD79a+), macrophages (Lectin RCA-1+), and astrocytes expressing glial fibrillary acidic protein. The virus showed marked neurotropism, and the neuropathology included multifocal to diffuse areas of gliosis and inflammation in the gray matter, neuronal degeneration, neuronophagia, vacuolation of the neuropil, focal necrosis, perivascular cuffing, and meningitis. Broad ranges in severity, neuroanatomical distribution, and type of cellular infiltrate were observed among the different bird species. Since neurotropism is a key feature of HPAI H5N1 infection in birds and other species and because the clinical presentation can vary, the characterization of the inflammation in the brain is important in understanding the pathogenesis of the disease and also has important diagnostic implications for sample selection.  相似文献   

9.
Large highly pathogenic avian influenza (HPAI) outbreaks caused by clade 2.3.4.4e H5N6 viruses occurred in Japan during the 2016–2017 winter. To date, several reports regarding these outbreaks have been published, however a comprehensive study including geographical and time course validations has not been performed. Herein, 58 Japanese HPAI virus (HPAIV) isolates from the 2016–2017 season were added for phylogenetic analyses and the antigenic relationships among the causal viruses were elucidated. The locations where HPAIVs were found in the early phase of the outbreaks were clustered into three regions. Genotypes C1, C5, and C6–8 HPAIVs were found in specific areas. Two strains had phylogenetically distinct hemagglutinin (HA) and non-structural (NS) genes from other previously identified strains, respectively. The estimated latest divergence date between the viral genotypes suggests that genetic reassortment occurred in bird populations before their winter migration to Japan. Antigenic differences in 2016–2017 HPAIVs were not observed, suggesting that antibody pressure in the birds did not contribute to the selection of HPAIV genotypes. In the late phase, the majority of HPAI cases in wild birds occurred south of the lake freezing line. At the end of the outbreak, HPAI re-occurred in East coast region, which may be due to the spring migration route of Anas bird species. These trends were similar to those observed in the 2010–2011 outbreaks, suggesting there is a typical pattern of seeding and dissemination of HPAIV in Japan.  相似文献   

10.
The ecology of avian influenza (AI) viruses in wild aquatic birds of Asia is poorly understood, especially for the H5N1 high pathogenicity AI (HPAI) viruses. From March 2006 through November 2008, 20 AI viruses were isolated in the Crimea region of Ukraine with an overall frequency of virus recovery of 3.3%. All the viruses were isolated from three species of dabbling ducks: mallard (Anas platyrhynchos), wigeon (Anas penelope), and garganey (Anas querquedula), making the frequency of virus recovery for dabbling ducks 6.3%. The viruses were predominantly isolated during the fall sampling period. All viruses were genetically and antigenically characterized. No H5N1 HPAI viruses were isolated, but other HA and NA subtypes were identified including H3N1 (2), H3N6 (3), H3N8 (4), H4N6 (6), H5N2 (3), H7N8 (1), and H10N6 (1) subtypes. All isolates were of low pathogenicity, as determined by the intravenous pathogenicity index of 0.00. For H5N2 and H7N8 isolates, the HA gene was sequenced and the phylogenetic analysis revealed possible ecologic connections of the Crimea region with AI viruses from Siberia and Europe. No influenza A isolates were recovered from other Anseriformes (diving ducks [two species of pochards] and graylag geese), Columbiformes (collared doves), Gruiformes (coot), and Galliformes (gray partridges).  相似文献   

11.
In contrast to chickens, there is a paucity of information on the potency of H5 vaccines to protect turkeys against the highly pathogenic avian influenza (HPAI) H5N1 virus infections. In this study, 4 groups, 10 turkey poults each, were vaccinated at seven days old with one of H5N2 or H5N1 commercial vaccines or one of two prepared H5N1 vaccines from a local Egyptian variant HPAI H5N1 (EGYvar/H5N1) strain. At 35 days age, all vaccinated and 10 non vaccinated birds were challenged intranasal with 10(6) EID(50)/0.1 ml of EGYvar/H5N1. All vaccines used in this study were immunogenic in turkeys. There was no cross reaction between the commercial vaccines and the Egyptian variant H5N1 antigen as obtained by the hemagglutination inhibition test. Birds vaccinated with H5N2 vaccine were died, while other H5N1 vaccinated groups have had 20-40% mortality. The highest virus excretion was found in non-vaccinated infected and H5N2 vaccinated birds. Eleven peculiar amino acid substitutions in H5 protein of the variant strain were existed neither in the vaccine strains nor in the earliest H5N1 virus introduced into Egypt in 2006. In conclusion, single vaccination at seven days old is inadequate for protection of meat turkeys against variant HPAI H5N1 challenge and multi-dose vaccination at older age is recommended. For the foreseeable future, continuous evaluation of the current vaccines in H5N1 endemic countries in the face of virus evolution is a paramount challenge to mitigate the socio-economic impact of the virus.  相似文献   

12.
H5 highly pathogenic avian influenza (HPAI) viruses have spread worldwide, and antigenic variants of different clades have been selected. In this study, the national stockpiled vaccine prepared from A/duck/Hokkaido/Vac-1/2004 (H5N1) strain was evaluated for the protective efficacy against H5N8 HPAI virus isolated in Kumamoto prefecture, Japan, in April 2014. In the challenge test, all of the vaccinated chickens survived without showing any clinical signs and reduced virus shedding. It was concluded that the present stockpiled vaccine was effective against the H5N8 HPAI virus.  相似文献   

13.
When highly pathogenic avian influenza H5N1 (HPAI H5N1) arrived at Lake Constance in February 2006, little was known about its ecology and epidemiology in wild birds. In order to prevent virus transmission from wild birds to poultry, the adjacent countries initiated the tri-national, interdisciplinary research program ?Constanze? to investigate avian influenza infections in water birds at Lake Constance. In collaboration with government agencies scientists examined the prevalence of AI virus in the region of Lake Constance for a period of 33 months, compared the effectiveness of different surveillance methods and analysed the migration behaviour of water birds. Although virus introduction from regions as far as the Ural Mountains seemed possible based on the migration behaviour of certain species, no influenza A viruses of the highly pathogenic subtype H5N1 (HPAIV) was found. However, influenza A viruses of different low pathogenic subtypes were isolated in 2.2 % of the sampled birds (swabs). Of the different surveillance methods utilised in the program the sampling of so called sentinel birds was particularly efficient.  相似文献   

14.
Highly pathogenic avian influenza (HPAI) was diagnosed in broiler breeders, submitted to the National Veterinary Research and Quarantine Service in South Korea. Grossly, the dead breeders had lesions consistent with HPAI, including pancreatic mottling, splenomegaly, pulmonary edema and congestion, and hemorrhages in the mucosa of the proventriculus, gizzard and small intestine, and on the serosal surface. Microscopically, there were necrotized hepatitis and pancreatitis, lymphocytic meningoencephalitis, myocarditis, and interstitial pneumonia. Influenza viral antigen was demonstrated in areas closely associated with histopathologic lesions. The AI virus was isolated from cecal tonsils, feces, trachea, and kidney of the chickens. The isolated virus was identified as the highly pathogenic H5N1, with a hemagglutinin proteolytic cleavage site deduced amino acid sequences of QREKRKKR/GLFGAGLFGAIAG. In order to determine the pathogenicity of the isolate, eight 6-week-old specific pathogen free chickens were inoculated intravenously with the virus, and all the birds died within 24 hr after inoculation. This is the first report of an outbreak of HPAI in the chickens in South Korea.  相似文献   

15.
Beginning in 2003, highly pathogenic avian influenza (HPAI) H5N1 virus spread across Southeast Asia, causing unprecedented epidemics. Thailand was massively infected in 2004 and 2005 and continues today to experience sporadic outbreaks. While research findings suggest that the spread of HPAI H5N1 is influenced primarily by trade patterns, identifying the anthropogenic risk factors involved remains a challenge. In this study, we investigated which anthropogenic factors played a role in the risk of HPAI in Thailand using outbreak data from the “second wave” of the epidemic (3 July 2004 to 5 May 2005) in the country. We first performed a spatial analysis of the relative risk of HPAI H5N1 at the subdistrict level based on a hierarchical Bayesian model. We observed a strong spatial heterogeneity of the relative risk. We then tested a set of potential risk factors in a multivariable linear model. The results confirmed the role of free-grazing ducks and rice-cropping intensity but showed a weak association with fighting cock density. The results also revealed a set of anthropogenic factors significantly linked with the risk of HPAI. High risk was associated strongly with densely populated areas, short distances to a highway junction, and short distances to large cities. These findings highlight a new explanatory pattern for the risk of HPAI and indicate that, in addition to agro-environmental factors, anthropogenic factors play an important role in the spread of H5N1. To limit the spread of future outbreaks, efforts to control the movement of poultry products must be sustained.  相似文献   

16.
Typically highly pathogenic avian influenza (HPAI) viruses spread very rapidly among chickens within sheds. However, the spread was slower than expected for the initial 10 days of the index farm in Japan during 2004. This slow spread, as well as the lack of gross lesions, clinical signs, or high mortality, hindered the field veterinarian from reporting a suspected HPAI outbreak to the veterinary office. To understand the field conditions for the slow virus spread, we examined contact and airborne transmission of the H5N1 virus to chickens in a negative-pressure isolator using various numbers of infected chickens and separate compartments. We found that the contact transmission did occur inefficiently when one or two chickens were infected, whereas the transmission was efficient when four chickens were infected. Airborne transmission of the HPAI virus was also dependent on the number of infected chickens and was less efficient than contact transmission. These data together with field observations suggested that number of infected chickens, chicken house types, and amount of environmental contamination might affect the virus transmission efficiency to chickens.  相似文献   

17.
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.  相似文献   

18.
Highly pathogenic avian influenza (HPAI) virus subtype H5N1 threatens poultry production and human health. Understanding the role that migratory waterfowl play in introducing and maintaining this infection is critical to control the outbreaks. A study was conducted to determine if the occurrence of HPAI subtype H5N1 outbreaks in village poultry in Romania, 2005-2006, was associated with proximity to populations of migratory waterfowl. Reported outbreaks--which could be grouped into three epidemic phases--and migratory waterfowl sites were mapped. The migratory waterfowl site closest to each outbreak was identified. The distances between outbreaks occurring in phase 1 and 2 of the epidemic and the closest migratory waterfowl site were significantly (P<0.001) less than in phase 3, but these distances were only useful in predicting when outbreaks occurred during phase 1 (October-December, 2005) of the epidemic. A spatial lag (rho=0.408, P=0.041) model best fit the data, using distance and [distance]*[distance] as predictors (R2=0.425). The correlation between when outbreaks were predicted to occur and when they were observed to occur was 0.55 (P=0.006). Results support the hypothesis that HPAI virus subtype H5N1 infections of village poultry in Romania during the autumn of 2005 might have occurred via exposure to migratory populations of waterfowl.  相似文献   

19.
In the present study, we used nucleotide and protein sequences of avian influenza virus H5N1, which were obtained in Asia and Africa, analyzed HA proteins using ClustalX1.83 and MEGA4.0, and built a genetic evolutionary tree of HA nucleotides. The analysis revealed that the receptor specificity amino acid of A/HK/213/2003, A/Turkey/65596/2006 and etc mutated into QNG, which could bind with á–2, 3 galactose and á–2, 6 galactose. A mutation might thus take place and lead to an outbreak of human infections of avian influenza virus. The mutations of HA protein amino acids from 2004 to 2009 coincided with human infections provided by the World Health Organization, indicating a “low–high–highest–high–low” pattern. We also found out that virus strains in Asia are from different origins: strains from Southeast Asia and East Asia are of the same origin, whereas those from West Asia, South Asia and Africa descend from one ancestor. The composition of the phylogenetic tree and mutations of key site amino acids in HA proteins reflected the fact that the majority of strains are regional and long term, and virus diffusions exist between China, Laos, Malaysia, Indonesia, Azerbaijan, Turkey and Iraq. We would advise that pertinent vaccines be developed and due attention be paid to the spread of viruses between neighboring countries and the dangers of virus mutation and evolution.  相似文献   

20.
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