Seroprevalance and identification of influenza A virus infection from migratory wild waterfowl in China (2004-2005)

Outbreaks of a highly pathogenic avian influenza (H5N1) were reported in birds in more than eight Asian countries. We sought to identify the origin of this infection, and herein report the results of serological and virological monitoring of migrant wild waterfowl in mainland China. From a total of 493 serum samples, collected from 15 migratory wild waterfowl species for 9 months (from June 2004 to May 2005) in mainland China, we detected only low-level antibodies against influenza subtypes H2, H9 and H10 in the relict gull, little egret, black-crowned night heron, bar-tailed godwit, whimbrel and the common greenshank. No virus was identified from the 1052 cloacal and oropharyngeal swabs except dead bar-headed geese. These data show that the influenza type A virus subtypes H2-H13 did not circulate at detectable levels within the sampled population.     

Influenza virus surveillance in waterfowl in Pennsylvania after the H5N2 avian outbreak

During the latter stages of the lethal H5N2 influenza eradication program in domestic poultry in Pennsylvania in 1983-84, surveillance of waterfowl was done to determine if these birds harbored influenza viruses that might subsequently appear in poultry. From late June to November 1984, 182 hemagglutinating viruses were isolated from 2043 wild birds, primarily ducks, in the same geographical area as the earlier lethal H5N2 avian influenza outbreak. The virus isolates from waterfowl included paramyxoviruses (PMV-1, -4, and -6) and influenza viruses of 13 antigenic combinations. There was only one H5N2 isolate from a duck. Although this virus was antigenically related to the lethal H5N2 virus, genetic and antigenic analysis indicated that it could be discriminated from the virulent family of H5N2 viruses, and it did not originate from chickens. Many of the influenza viruses obtained from wild ducks were capable of replicating in chickens after experimental inoculation but did not cause disease. These studies show that many influenza A virus strains circulating in waterfowl in the vicinity of domestic poultry in Pennsylvania did not originate from domestic poultry. These influenza viruses from wild ducks were capable of infecting poultry; however, transmission of these viruses to poultry apparently was avoided by good husbandry and control measures.     

一株野鸟源重组禽流感(H6N1)病毒基因组分子特征分析

2017年在江苏省野生豆雁粪便中分离得到1株H6N1亚型禽流感病毒A/Anser fabalis/Jiangsu/J746/2017(H6N1)(J746)。本研究对J746进行了全基因组测序,并对其进行了遗传进化分析。遗传进化分析结果表明:与HA和NA基因同源性最高的毒株为A/wild waterfowl/Korea/F14-5/2016(H6N1),同源性为99.4%。HA基因与流行于韩国、日本和孟加拉的N1、N2、N8亚型毒株处于同一分支,NA基因与韩国野生水禽的H6、H7亚型毒株处于同一分支,PB2基因与中亚及东亚地区低致性病毒株处于同一分支,PB1基因和NP基因与流行在东南亚的低致病性毒株处于同一分支,PA基因和M基因均处于欧亚分支,但PA形成了独立的小分支,NS基因与分离于中国中南部和日本的毒株聚集在一起。氨基酸位点分析表明,神经氨酸(NA)蛋白存在H274Y突变,该突变可增强病毒对神经氨酸酶抑制剂药物的耐药性;同时在PB2蛋白中发现与增强对小鼠致病性有关的L89V突变,在NS1蛋白中发现与增强对小鼠致病性、提高复制能力和改变宿主嗜性有关的P42S、L103F、I106M、N205S突变。综上所述,J746毒株基因组构成来源复杂,是由多个国家和地区形成的一株多元重组病毒。     

Isolation of influenza A viruses from migratory waterfowl in San-in District, western Japan in the winter of 1983-1984

Certain species of winter migratory waterfowl in San-in District, western Japan, were surveyed for influenza virus from November 1983 to March 1984. Faeces of the waterfowl were collected regularly at five stations. Eleven influenza A viruses including H5N3 and H10N4 subtypes were isolated from 450 faecal samples from whistling swans, 28 viruses including H2N2 and H10N4 subtypes were isolated from 362 faecal samples from pintails; and subtype H13N6 was isolated from 240 faecal samples of black-tailed gulls.     

Wildlife surveillance associated with an outbreak of lethal H5N2 avian influenza in domestic poultry

Wildlife surveillance was conducted for influenza viruses in conjunction with the 1983-84 lethal H5N2 avian influenza epizootic in domestic poultry in Pennsylvania, New Jersey, Maryland, and Virginia. Virus-isolation attempts made on cloacal and tracheal swabs from 4,466 birds and small rodents within the quarantined areas and 1,511 waterfowl in nearby Maryland yielded only a single H5N2 isolate from a pen-raised chukar in Pennsylvania. Antibodies against hemagglutinin type 5 and/or neuraminidase type 2 were found in 33% of the aquatic birds tested; however, this finding could not be used to confirm previous H5N2 avian influenza virus activity because of the possibility of prior infections with multiple influenza subtypes. The low prevalence of lethal H5N2 avian influenza virus in wild birds and small rodents strongly indicated that these animals were not responsible for dissemination of the disease among poultry farms during the outbreak.     

Influenza viruses and paramyxoviruses in ducks in the Atlantic flyway, 1977-1983, including an H5N2 isolate related to the virulent chicken virus

From 1977 to 1983, waterfowl migrating along the Atlantic flyway were annually monitored for orthomyxoviruses and paramyxoviruses in an area in central New York State. A total of 168 influenza isolates were obtained from 1,430 waterfowl. Twenty-four combinations of hemagglutinin and neuraminidase subtypes were detected, with as many as 12 found in a single year. One combination, an H5N2 isolate in 1982, was closely related to the virulent chicken virus that appeared in Pennsylvania in 1983. The prevalence of influenza varied greatly among the common waterfowl species: mallards 42%, black ducks 30%, blue-winged teal 11%, wood ducks 2%, and Canada geese 0%. A total of 89 paramyxoviruses were also from these waterfowl. In contrast to findings with influenza virus, the prevalence of paramyxoviruses did not differ significantly among the duck species. Serotype 1 (Newcastle disease virus) was predominant; three other serotypes were also identified. These findings indicated that ducks in the Atlantic flyway continually harbor influenza viruses and paramyxoviruses. The viruses may be a source of infection for other species.     

Novel human H7N9 influenza virus in China

Outbreaks of H7N9 avian influenza in humans in 5 provinces and 2 municipalities of China have reawakened concern that avian influenza viruses may again cross species barriers to infect the human population and thereby initiate a new influenza pandemic. Evolutionary analysis shows that human H7N9 influenza viruses originated from the H9N2, H7N3 and H11N9 avian viruses, and that it is as a novel reassortment influenza virus. This article reviews current knowledge on 11 subtypes of influenza A virus from human which can cause human infections.     

Seroprevalence and genetic characteristics of five subtypes of influenza A viruses in the Chinese pig population: A pooled data analysis

A literature review and pooled data analysis were carried out to examine the prevalence of antibodies against five influenza virus subtypes in pigs in China over a 10-year period (1999–2009). The average seropositive frequencies of subtypes H1, H3, H5, H7 and H9 were 3478/11,168 (31.1%), 2900/10,139 (28.6%), 77/5945 (1.3%), 0/1440 (0%) and 86/3619 (2.4%), respectively. There was a geographical variation in the seroprevalence of subtype H1, with the highest seroprevalence in pigs in South and East China. BLAST analysis of genetic sequences revealed that genome segments with moderate homology to the 2009 pandemic influenza A (H1N1) virus were present among swine influenza viruses isolated in China, especially in South and East China. It was concluded from both serological and genetic studies that subtypes H1, H3, H5 and H9 are currently co-circulating in pigs in China, with the H1 subtype most commonly detected, followed by H3.     

Serological evidence for influenza virus infection in Korean wild boars

Serum samples from 1,011 wild boars hunted in 2012 were collected for serological surveillance for 4 subtypes (pandemic A (H1N1) 2009 and classical H1N1, H1N2 and H3N2) of swine influenza virus (SIV). Samples from 12 of the boars were identified as positive for SIV (pandemic A (H1N1) 2009, n=9; classical H1N1, n=2; and H1N2, n=1) by a hemagglutination inhibition test (HI test) and a nucleoprotein (NP)-based enzyme-linked immunosorbent assay (NP-ELISA). Although the overall seroprevalence of SIV in the Korean wild boar population was somewhat low compared with that in China and the U.S.A., the apparent prevalence of pandemic H1N1 was notable. Therefore, continuous monitoring of the wild boar population is needed as it may be a major reservoir for pandemic H1N1, facilitating its spread to humans and domestic pigs.     

禽流感病毒N4亚型神经氨酸酶基因的克隆和序列分析

应用无特定病原体 (SPF)鸡胚增殖禽流感病毒 A/ Turkey/ Ontario/ 6 118/ 6 8(H8N4 )毒株 ,Tri Zol L S Reagent提取病毒 RNA,RT- PCR扩增神经氨酸酶 (NA)基因全片段 ,克隆到 p MD18- T载体上 ,并进行了鉴定和序列测定。所获得的 NA基因片段长 14 4 1bp,编码 4 90个氨基酸残基。根据推导的氨基酸序列进行预测 ,有 9个潜在的糖基化位点和2 0个半胱氨酸残基     

H9N2亚型禽流感病毒血凝素和神经氨酸酶基因的遗传分析

H9N2亚型禽流感病毒自1994年在中国首次发现以来,一直在家禽中流行,其导致的产蛋下降和发病死亡给养禽业发展带来严重危害。以前的研究发现中国的H9N2亚型禽流感病毒在进化过程中形成多个基因型,其表面抗原蛋白血凝素基因(HA)可被划分为以A/chicken/Beijing/1/94、A/quail/Hong Kong/G1/97(G1)和A/chicken/Heilongjiang/35/01等为代表的3个亚群,神经氨酸酶基因(NA)可被划分为以A/chicken/Beijing/1/94、A/quail/Hong Kong/G1/97(G1)和A/chicken/Hong Kong/G9/97(G9)等为代表的3个亚群。其中类G1病毒的HA基因只在香港分离株中出现。本研究对我国2003年～2004年从禽类中分离的H9N2亚型禽流感病毒血凝素(HA)和神经氨酸酶(NA)基因进行测定和遗传演化分析,结果表明其中11株病毒的HA基因属于CK/BJ/1/94群系,NA基因属于CK/BJ/1/94或DK/HK/G9/97群系,并首次发现两株病毒含有类G1病毒HA和NA基因,而且这些类G1病毒具有不同的抗原性以及人流感病毒的受体结合位点。本研究结果提示应对H9N2病毒的防治及其公共卫生意义予以高度重视。     

野生鸟类禽流感病毒感染情况的调查

为了解野生鸟类禽流感病毒(AIV)的携带感染情况,2006年～2010年,本研究在湖南省主要候鸟迁徙地收集115只野鸟组织或拭子样品、75份野鸟的新鲜粪便样品和72份血清样品。组织或拭子样品采用RT-PCR方法检测和鸡胚接种病毒分离鉴定,血清样品分别进行H5(含Re-5和Re-4)、H6、H7、H9、H10和H11抗体检测。结果表明,从斑鸠和绿头鸭组织中分别分离到H5N1亚型和H3N2亚型AIV;72份血清中有17份抗体为阳性,其中H5(Re-5)亚型5份、H5(Re-4)亚型1份、H6亚型1份、H7亚型2份和H9亚型8份,阳性率分别为6.94%、1.39%、1.39%、2.78%和11.11%。H10和H11亚型未检测到抗体阳性。     

Molecular characterization of an influenza A virus (H4N2) isolated from waterfowl habitats in the State of Mexico

Wild waterfowl and their habitats are the main reservoirs of influenza A virus (IAV) mainly during the breeding season and prior to migration. This study describes the molecular characterization of an IAV isolated from 240 water samples of a small wetland during non-breeding season of migratory wild ducks in the State of Mexico, Mexico. The results showed that the virus belongs to the H4N2 subtype and each of its eight segments of the viral genome has similarity to IAV isolated from ducks in North America. This study suggests that IAV can be isolated from small wetland during non-breeding season of migrating waterfowl.     

An H9N2 influenza virus vaccine prepared from a non-pathogenic isolate from a migratory duck confers protective immunity in mice against challenge with an H9N2 virus isolated from a girl in Hong Kong

H9N2 influenza viruses circulate in wild birds and poultry in Eurasian countries, and have been isolated from pigs and humans in China. H9N2 viruses isolated from birds, pigs and humans have been classified into three sublineages based on antigenic and genetic features. Chicken antisera to H9N2 viruses of the Korean sublineage reacted with viruses of different sublineages by the hemagglutination-inhibition test. A test vaccine prepared from a non-pathogenic A/duck/Hokkaido/49/1998 (H9N2) strain of the Korean sublineage, obtained from our influenza virus library, induced immunity in mice to reduce the impact of disease caused by the challenge with A/Hong Kong/1073/1999 (H9N2), which is of a different sublineage. The present results indicate that an inactivated whole virus vaccine prepared from a non-pathogenic influenza virus from the library could be used as an emergency vaccine during the early stage of a pandemic caused by H9N2 infection.     

Recent developments in avian influenza research: epidemiology and immunoprophylaxis

Influenza A viruses have been isolated from humans, from several other mammalian species and a wide variety of avian species, among which, wild aquatic birds represent the natural hosts of influenza viruses. The majority of the possible combinations of the 15 haemagglutinin (HA) and nine neuraminidase (NA) subtypes recognized have been identified in isolates from domestic and wild birds. Infection of birds can cause a wide range of clinical signs, which may vary according to the host, the virus strain, the host's immune status, the presence of any secondary exacerbating microorganisms and environmental factors. Most infections are inapparent, especially in waterfowl and other wild birds. In contrast, infections caused by viruses of H5 and H7 subtypes can be responsible for devastating epidemics in poultry. Despite the warnings to the poultry industry about these viruses, in 1997 an avian H5N1 influenza virus was directly transmitted from birds to humans in Hong Kong and resulted in 18 confirmed infections, thus strengthening the pandemic threat posed by avian influenza (AI). Indeed, reassortant viruses, harbouring a combination of avian and human viral genomes, have been responsible for major pandemics of human influenza. These considerations warrant the need to continue and broaden efforts in the surveillance of AI. Control programmes have varied from no intervention, as in the case of the occurrence of low pathogenic (LP) AI (LPAI) viruses, to extreme, expensive total quarantine-slaughter programmes carried out to eradicate highly pathogenic (HP) AI (HPAI) viruses. The adoption of a vaccination policy, targeted either to control or to prevent infection in poultry, is generally banned or discouraged. Nevertheless, the need to boost eradication efforts in order to limit further spread of infection and avoid heavy economic losses, and advances in modern vaccine technologies, have prompted a re-evaluation of the potential use of vaccination in poultry as an additional tool in comprehensive disease control strategies. This review presents a synthesis of the most recent research on AI that has contributed to a better understanding of the ecology of the virus and to the development of safe and efficacious vaccines for poultry.     

The characterization of low pathogenic avian influenza viruses isolated from wild birds in northern Vietnam from 2006 to 2009

Due to concerns that wild birds could possibly spread H5N1 viruses, surveillance was conducted to monitor the types of avian influenza viruses circulating among the wild birds migrating to or inhabiting in northern Vietnam from 2006 to 2009. An H5N2 virus isolated from a Eurasian woodcock had a close phylogenetic relationship to H5 viruses recently isolated in South Korea and Japan, suggesting that H5N2 has been shared between Vietnam, South Korea, and Japan. An H9N2 virus isolated from a Chinese Hwamei was closely related to two H9N2 viruses that were isolated from humans in Hong Kong in 2009, suggesting that an H9N2 strain relevant to the human isolates had been transmitted to and maintained among the wild bird population in Vietnam and South China. The results support the idea that wild bird species play a significant role in the spread and maintenance of avian influenza and that this also occurs in Vietnam.