Neurotropism of highly pathogenic avian influenza virus A/chicken/Indonesia/2003 (H5N1) in experimentally infected pigeons (Columbia livia f. domestica)

This investigation assessed the susceptibility of experimentally infected pigeons to the highly pathogenic avian influenza virus (HPAIV) H5N1 that caused recent outbreaks of avian influenza in birds and humans in several countries of Asia. For this purpose 14 pigeons were infected ocularly and nasally with 10(8) EID50 and clinical signs were recorded and compared with five chickens infected simultaneously as positive controls. The chickens demonstrated anorexia, depression, and 100% mortality within 2 days postinoculation. Three of the pigeons died after a history of depression and severe neurological signs consisting of paresis to paralysis, mild enteric hemorrhage, resulting in a mortality of 21%. Gross lesions in these pigeons were mild and inconsistent. Occasionally subcutaneous hyperemia and hemorrhage and cerebral malacia were observed. Microscopic lesions and detection of viral antigen were confined to the central nervous system of these pigeons. In the cerebrum and to a minor extent in the brain stem a lymphohistiocytic meningoencephalitis with disseminated neuronal and glial cell necrosis, perivascular cuffing, glial nodules, and in one bird focally extensive liquefactive necrosis could be observed. The remaining nine pigeons showed neither clinical signs nor gross or histological lesions associated with avian influenza, although seroconversion against H5 indicated that they had been infected. These results confirm that pigeons are susceptible to HPAIV A/chicken/Indonesia/2003 (H5N1) and that the disease is associated with the neurotropism of this virus. Although sentinel chickens and most pigeons did not develop disease, further experiments have to elucidate whether or not Columbiformes are involved in transmission and spread of highly pathogenic avian influenza.     

Review of the literature on avian influenza A viruses in pigeons and experimental studies on the susceptibility of domestic pigeons to influenza A viruses of the haemagglutinin subtype H7

The scientific literature of the past century is reviewed on fowl plague (presently termed highly pathogenic avian influenza, HPAI) in pigeons. HPAI viruses cause epidemic disease outbreaks with high rates of losses in many avian species, particularily in chickens and turkeys. Also susceptible to disease are quails, guinea fowl, ducks, geese, ostriches, passerine birds, and birds of prey whereas conflicting reports on the susceptibility of the domestic pigeon exist. Based on literature reports and on own experiments, and applying as criteria for judgements clinically overt forms of disease, virus multiplication plus shedding and seroconversion, it is concluded that domestic pigeons are only partially susceptible to influenza A viruses of the haemagglutinin subtype H7. Infection of pigeons with H7 viruses results only in some of them in signs, virus shedding and seroconversion. Using the same criteria, pigeons appear to be even less susceptible to infection with influenza A viruses of the H5 subtype. Only one of five publications describe in 1/19 pigeons exposed to H5 influenza A virus depression one day before death, and only 2/19 multiplied and excreted virus, and 1/19 developed circulating antibodies. Consequently, pigeons play only a minor role in the epidemiology of H5 influenza viruses. In contrast, following infection with influenza A virus of the subtype H7 clinical signs in pigeons consist of conjunctivitis, tremor, paresis of wings and legs, and wet droppings. H7-infected pigeons multiply and excrete H7 viruses and develop circulating antibodies. Albeit of the status of infection, free-flying domestic pigeons can act as mechanical vectors and vehicles for long-distance transmission of any influenza A virus if plumage or feet were contaminated.     

Pathogenicity of a Hong Kong-origin H5N1 highly pathogenic avian influenza virus for emus, geese, ducks, and pigeons

The H5N1 type A influenza viruses that emerged in Hong Kong in 1997 are a unique lineage of type A influenza viruses with the capacity to transmit directly from chickens to humans and produce significant disease and mortality in both of these hosts. The objective of this study was to ascertain the susceptibility of emus (Dramaius novaehollandiae), domestic geese (Anser anser domesticus), domestic ducks (Anas platyrhynchos), and pigeons (Columba livia) to intranasal (i.n.) inoculation with the A/chicken/Hong Kong/220/97 (H5N1) highly pathogenic avian influenza virus. No mortality occurred within 10 days postinoculation (DPI) in the four species investigated, and clinical disease, evident as neurologic dysfunction, was observed exclusively in emus and geese. Grossly, pancreatic mottling and splenomegaly were identified in these two species. In addition, the geese had cerebral malacia and thymic and bursal atrophy. Histologically, both the emus and geese developed pancreatitis, meningoencephalitis, and mild myocarditis. Influenza viral antigen was demonstrated in areas with histologic lesions up to 10 DPI in the geese. Virus was reisolated from oropharyngeal and cloacal swabs and from the lung, brain, and kidney of the emus and geese. Moderate splenomegaly was observed grossly in the ducks. Viral infection of the ducks was pneumotropic, as evidenced by mild inflammatory lesions in the respiratory tract and virus reisolation from oropharyngeal swabs and from a lung. Pigeons were resistant to HK/220 infection, lacking gross and histologic lesions, viral antigen, and reisolation of virus. These results imply that emus and geese are susceptible to i.n. inoculation with the HK/220 virus, whereas ducks and pigeons are more resistant. These latter two species probably played a minimal epidemiologic role in the perpetuation of the H5N1 Hong Kong-origin influenza viruses.     

Surveillance for highly pathogenic avian influenza in wild birds in the USA

As part of the USA's National Strategy for Pandemic Influenza, an Interagency Strategic Plan for the Early Detection of Highly Pathogenic H5N1 Avian Influenza in Wild Migratory Birds was developed and implemented. From 1 April 2006 through 31 March 2009, 261 946 samples from wild birds and 101 457 wild bird fecal samples were collected in the USA; no highly pathogenic avian influenza was detected. The United States Department of Agriculture, and state and tribal cooperators accounted for 213 115 (81%) of the wild bird samples collected; 31, 27, 21 and 21% of the samples were collected from the Atlantic, Pacific, Central and Mississippi flyways, respectively. More than 250 species of wild birds in all 50 states were sampled. The majority of wild birds (86%) were dabbling ducks, geese, swans and shorebirds. The apparent prevalence of low pathogenic avian influenza viruses during biological years 2007 and 2008 was 9.7 and 11.0%, respectively. The apparent prevalence of H5 and H7 subtypes across all species sampled were 0.5 and 0.06%, respectively. The pooled fecal samples (n= 101 539) positive for low pathogenic avian influenza were 4.0, 6.7 and 4.7% for biological years 2006, 2007 and 2008, respectively. The highly pathogenic early detection system for wild birds developed and implemented in the USA represents the largest coordinated wildlife disease surveillance system ever conducted. This effort provided evidence that wild birds in the USA were free of highly pathogenic avian influenza virus (given the expected minimum prevalence of 0.001%) at the 99.9% confidence level during the surveillance period.     

Limited susceptibility of pigeons experimentally inoculated with H5N1 highly pathogenic avian influenza viruses

An experimental infection study was performed using pigeons reared for racing or meat production in Japan and clade 2.2 and 2.3.2 isolates of H5N1 highly pathogenic avian influenza virus to evaluate the possible role of pigeons in virus transmission to poultry. In experiment 1, when 20 pigeons were intranasally inoculated with high or low viral doses, no inoculated pigeon exhibited clinical signs for 14 days. Drinking water and almost all swab samples were negative for virus isolation. Virus isolation was positive in 3 oral swab samples from 2 pigeons from day 2 through 4 postinoculation, but viral titers of positive samples were extremely low. Immunohistochemical analysis for virus detection was negative in all tissue samples. Along with seroconversion in a limited number of pigeons postinoculation, these results suggest that pigeons have limited susceptibility to the virus used for experimental infection. In experiment 2, when uninoculated chickens were housed with virus-inoculated pigeons, all pigeons and contact chickens survived for 14 days without exhibiting any clinical signs. According to serological analysis, the chickens did not exhibit seroconversion after close contact with inoculated pigeons. Our data suggest that the risk posed by pigeons with respect to the transmission of the H5N1 highly pathogenic avian influenza virus to poultry would be less than that for other susceptible avian species.     

Isolation of myxoviruses from migratory waterfowls in San-in district,western Japan in winters of 1997-2000

Between November 1997 and February 2000, winter migratory waterfowls of several species staying in San-in district, western Japan were surveyed for influenza A virus and paramyxovirus at four stations. A total of 18 influenza A viruses was isolated from 1,404 fecal samples of whistling swans, pintails, mallards, and white-fronted geese. Five different hemagglutinins and eight neuraminidases were identified in the viruses isolated, in 11 different combinations, including H7N8 related to a subtype of a highly pathogenic chicken virus. In 2000, five lentogenic (non-pathogenic) Newcastle disease viruses were also isolated from white-fronted geese. These results suggested that possible precursor viruses for highly pathogenic avian myxoviruses are still brought into Japan by migratory waterfowls. The results also support the contention that continued surveillance of wild waterfowl population should be an integral part of control policies for these serious poultry diseases.     

Highly pathogenic avian influenza virus subtype H5N1 in Mute swans in the Czech Republic

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.     

Effect of a prior exposure to a low pathogenic avian influenza virus in the outcome of a heterosubtypic low pathogenic avian influenza infection in mallards (Anas platyrhynchos)

Wild birds, particularly Anseriformes and Charadriiformes, are considered the natural reservoir of low pathogenic avian influenza (LPAI) viruses. The high prevalence and subtype diversity of avian influenza viruses at premigrational staging areas provide the perfect opportunity for multiple exposures to different LPAI virus subtypes. Natural consecutive and concurrent infections of sentinel ducks with different LPAI virus subtypes have been reported. The protective immune response from different LPAI virus infections is not understood nor is the effect of such repeated exposures. This study experimentally evaluated the effect of a prior exposure to a LPAI virus on the outcome of a heterosubtypic LPAI virus infection in mallards (Anas platyrhynchos). The results of this investigation suggest that recent prior exposure to a LPAI virus may affect the outcome of a subsequent heterosubtypic LPAI infection in mallards by reducing the duration of cloacal and oropharyngeal viral shedding as well as the viral load excreted via the cloaca. Wild mallards are likely exposed to multiple subtypes of LPAI virus during the periods of peak viral circulation, and the results of this study suggest that the duration of viral shedding in subsequent exposures might be reduced.     

抗禽流感病毒H5和H9亚型血凝素特异性单克隆抗体的研制及应用

以禽流感题H5和H9亚型病毒分别免疫Balh／c小鼠，取其脾细胞与SP2／0的骨髓瘤细胞融合，用血凝抑制试验(HI）检测细胞培养上清，结果获得了6株特异性单克隆抗体，其中抗禽流感题亚型病毒血凝素特异性单克隆抗体细胞株3株，分别命名为4B6、4A3、3H1；抗H9亚型病毒血凝素单克隆抗体细胞株3株，命名为6E6、6B6和5B4。这些单克隆抗体小鼠腹水HI效价为2^13-15，细胞培养上清抗体HI效价为2^7-8。研究结果表明，所有这些单克隆抗体仅与试验的相应题或ID亚型病毒株发生特异性反应，而不能与鸡新城疫病毒、鹅新城疫病毒、鹅腺病毒和鸡产蛋下降综禽征病毒(EDS76)等反应。实验室检测结果证明，应用这些单克隆抗体能在24h内迅速检测出相应的禽流感病毒。所有这些单克隆抗体将在禽流感的预警预报工作中发挥重要作用。     

Serologic surveillance of swine H1 and H3 and avian H5 and H9 influenza A virus infections in swine population in Korea

Influenza A is a respiratory disease common in the swine industry. Three subtypes, H1N1, H1N2 and H3N2 influenza A viruses, are currently co-circulating in swine populations in Korea. An outbreak of the highly pathogenic avian influenza H5N1 virus occurred in domestic bird farms in Korea during the winter season of 2003. Pigs can serve as hosts for avian influenza viruses, enabling passage of the virus to other mammals and recombination of mammalian and avian influenza viruses, which are more readily transmissible to humans. This study reports the current seroprevalence of swine H1 and H3 influenza in swine populations in Korea by hemagglutination inhibition (HI) assay. We also investigated whether avian H5 and H9 influenza transmission occurred in pigs from Korea using both the HI and neutralization (NT) tests. 51.2% (380/742) of serum samples tested were positive against the swine H1 virus and 43.7% (324/742) were positive against the swine H3 virus by HI assay. The incidence of seropositivity against both the swine H1 virus and the swine H3 virus was 25.3% (188/742). On the other hand, none of the samples tested showed seropositivity against either the avian H5 virus or the avian H9 virus by the HI and NT tests. Therefore, we report the high current seroprevalence and co-infectivity of swine H1 and H3 influenza viruses in swine populations and the lack of seroepidemiological evidence of avian H5 and H9 influenza transmission to Korean pigs.     

Development and evaluation of a DAS-ELISA for rapid detection of avian influenza viruses

Rapid detection of avian influenza virus (AIV) infection is critical for control of avian influenza (AI) and for reducing the risk of pandemic human influenza. A double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was developed for this purpose. The method employed a monoclonal antibody (MAb) as the capture antibody and rabbit polyclonal IgG labeled with horseradish peroxidase as the detector antibody, and both antibodies were against type-specific influenza A nucleoprotein (NP). The DAS-ELISA could detect minimally 2.5 ng of influenza viral protein in virus preparations treated with Triton X-100, which is equvilent to 2.5 x 10(2) EID50 virus particles. This DAS-ELISA could detect all 15n AIV subtypes (H1-H15) and did not cross react with other avian pathogens tested. The DAS-ELISA were directly compared with virus isolation (VI) in embryonated chicken eggs, the current standard of influenza virus detection, for 805 chicken samples. The DAS-ELISA results correlated with VI results for 98.6% of these samples, indicating a sensitivity of 97.4% and specificity of 100%. The method was further tested with H5N1 and H9N2 AIV experimentally infected chickens, ducks, and pigeons, as well as field samples obtained from central China in 2005. The DAS-ELISA method has demonstrated application potential as an AIV screening tool and as a supplement for virus isolation in Asia.     

Health status of free-living pigeons (Columba livia domestica) in the city of Ljubljana

In the year 2000 an epidemiological research was undertaken on the health status of free-living pigeons in the city of Ljubljana, Slovenia. A total of 139 pigeons were captured and examined for the most common bacterial, viral, and parasitic diseases. Serum samples, oropharyngeal and cloacal swabs as well as samples of droppings and feathers were taken from the captured birds. Antibodies to paramyxovirus type 1 were found in 84.2% of the sera examined, and 23.7% of birds were serologically positive to Chlamydophila psittaci. Antibodies to avian influenza virus were not detected. Salmonella spp. were isolated from 5.7% of the cloacal swabs. Trichomonas gallinae was clinically suspected and then microscopically confirmed using oropharyngeal swabs in 7.9% of examined birds. Eimeria spp. was identified in 71.9%, Capillaria sp. in 26.6% and Ascaridia columbae in 4.3% of droppings samples examined. Of the ectoparasites, Columbicola columbae and Campanulotes bidentatus compar were found.     

Low Pathogenic Avian Influenza (H7N1) Transmission Between Wild Ducks and Domestic Ducks

This article describes a virological investigation in a mixed flock of ducks and geese following detection of avian influenza virus antibodies in domestic geese. Low pathogenic H7N1 was found in both domestic and wild birds, indicating that transmission of virus was likely to have taken place between these. The importance of implementing and maintaining appropriate biosecurity measures is re‐emphasized.     

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.     

Antiviral efficacy of oseltamivir against avian influenza virus in avian species

Avian influenza is one of the most contagious viral diseases in bird species and, increasingly, interspecies transmission to mammalian species has been reported. Prevention and eradication of avian influenza virus (AIV) infection in birds may require vaccines as part of a comprehensive program including biosecurity, culling, diagnostics, and surveillance. However, for valuable bird species in zoos, novel eradication strategies are needed, including antiviral treatments. The present study evaluated the anti-influenza efficacy of the potent neuraminidase inhibitor oseltamivir in avian species using the orders Galliformes (chickens) and Anseriformes (ducks). Viral replication of low pathogenic AIV was significantly reduced in the chicken model and completely reduced in the duck model. Anti-influenza drug administration to valuable bird species with an appropriate extrapolation approach could be useful for control of AIV in combination with active surveillance and vaccination strategies. Further, evaluation of oseltamivir against highly pathogenic avian influenza (HPAI) using avian models would be needed to optimize the oseltamivir application guideline for HPAI control.     

新疆一起鹅源高致病性禽流感病毒鉴定初报

对新疆塔城市发生的一起临床怀疑为高致病性禽流感疫情进行流行病学调查,并采用血凝抑制试验、RT—PCR和禽流感通用荧光RT—PCR对血清及病料进行初步鉴定和诊断,结果表明,该病例为高致病性禽流感疑似疫情,后经国家禽流感参考实验室确诊为H5NI型高致病性禽流感,这是新疆首次发现鹅高致病性禽流感。     

Newcastle disease and avian influenza A virus in wild waterfowl in South Africa

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.