Avian influenza, an infectious disease of birds, is caused by type A strain of the influenza virus. The disease, which was first identified in Italy more than 100 years ago, occurs worldwide. Avian influenza viruses are mainly distributed by migratory birds. Various animals like birds, pigs, horses, sea mammals and, finally, humans are susceptible to influenza A viruses. The high possibility of genomic changes like gene shift and drift are caused by the segmented RNA genome.
Matched MeSH terms: Influenza in Birds/mortality; Influenza in Birds/epidemiology; Influenza in Birds/prevention & control; Influenza in Birds/transmission*; Influenza in Birds/virology
Biotechnology-based detection systems and sensors are in use for a wide range of applications in biomedicine, including the diagnostics of viral pathogens. In this review, emerging detection systems and their applicability for diagnostics of viruses, exemplified by the case of avian influenza virus, are discussed. In particular, nano-diagnostic assays presently under development or available as prototype and their potentials for sensitive and rapid virus detection are highlighted.
Matched MeSH terms: Influenza in Birds/diagnosis; Influenza in Birds/virology*
Since the first H5N1 highly pathogenic avian influenza virus (HPAIV) infection in the region in August 2003, Cambodia, Laos, Malaysia, Myanmar, Indonesia, Thailand and Vietnam have all recorded outbreaks of the disease. The HPAIV continues to occur in some countries in Southeast Asia despite control programmes encompassing surveillance, vaccination and stamping out strategies. A number of strains have been circulating in the region since the first outbreaks in 2003, and although the source of the initial outbreaks in domestic poultry is not known, the continuing propagation of disease in the region is primarily the result of the movement of domestic poultry and poultry products, and people. A comprehensive approach using all the strategies available to break the chain of transmission of the virus in poultry will be needed to achieve lasting disease control.
Matched MeSH terms: Influenza in Birds/epidemiology*; Influenza in Birds/prevention & control
Depopulation of birds has always been an effective method not only to control the transmission of avian influenza in bird populations but also to eliminate influenza viruses. We introduce a Filippov avian-only model with culling of susceptible and/or infected birds. For each susceptible threshold level [Formula: see text], we derive the phase portrait for the dynamical system as we vary the infected threshold level [Formula: see text], focusing on the existence of endemic states; the endemic states are represented by real equilibria, pseudoequilibria and pseudo-attractors. We show generically that all solutions of this model will approach one of the endemic states. Our results suggest that the spread of avian influenza in bird populations is tolerable if the trajectories converge to the equilibrium point that lies in the region below the threshold level [Formula: see text] or if they converge to one of the pseudoequilibria or a pseudo-attractor on the surface of discontinuity. However, we have to cull birds whenever the solution of this model converges to an equilibrium point that lies in the region above the threshold level [Formula: see text] in order to control the outbreak. Hence a good threshold policy is required to combat bird flu successfully and to prevent overkilling birds.
Matched MeSH terms: Influenza in Birds/prevention & control*; Influenza in Birds/transmission
Between December 2003 and January 2004 highly pathogenic avian influenza (HPAI) H5N1 infections of poultry were declared in China, Japan, South Korea, Laos, Thailand, Cambodia, Vietnam, and Indonesia. In 2004 an outbreak was reported in Malaysia. In 2005 H5N1 outbreaks were recorded in poultry in Russia, Kazakhstan, Mongolia, Romania, Turkey, and Ukraine, and virus was isolated from swans in Croatia. In 2004 HPAI H5N1 virus was isolated from smuggled eagles detected at the Brussels Airport and in 2005 imported caged birds held in quarantine in England. In 2006 HPAI was reported in poultry in Iraq, India, Azerbaijan, Pakistan, Myanmar, Afghanistan, and Israel in Asia; Albania, France, and Sweden in Europe; and Nigeria, Cameroon, and Niger in Africa; as well as in wild birds in some 24 countries across Asia and Europe. In 2003, over 25,000,000 birds were slaughtered because of 241 outbreaks of HPAI caused by virus of H7N7 subtype in the Netherlands. The virus spread into Belgium (eight outbreaks) and Germany (one outbreak). HPAI H5N2 virus was responsible for outbreaks in ostriches in South Africa during 2005. HPAI H7N3 virus was isolated in Pakistan in 2004. Low-pathogenicity avian influenza (LPAI) H5 or H7 viruses were isolated from poultry in Italy (H7N3 2002-2003; H5N2 2005), The Netherlands (H7N3 2002), France (H5N2 2003), Denmark (H5N7 2003), Taiwan (H5N2 2004), and Japan (H5N2 2005). Many isolations of LPAI viruses of other subtypes were reported from domestic and wild birds. Infections with H9N2 subtype viruses have been widespread across Asia during 2002-06.
Matched MeSH terms: Influenza in Birds/epidemiology*; Influenza in Birds/virology*
Avian influenza or bird flu is a common problem of domestic and wild birds. Some of its strains are able to cross the species barrier and cause infection in various members of class Mammalia. In view of relatively lesser efficacy of vaccines, antiviral therapies remain the only choice for the sustenance of mammals acquiring this highly devastating infection. This study is based on the evaluation of antiviral potential of methanol extracts of eleven selected Cholistani plants. The methanol extracts were prepared by using dried plants material followed by concentrating in a rotary evaporator and finally air dried before dissolving in nanopure water. The suspension was filter sterilized and subjected to in ovo antiviral assays. The allantoic fluids were harvested and haemagglutinin (HA) titers were determined. Among the eleven plants evaluated all methanol extracts were found effective against AIV H9N2 except S. baryosma extract. The medicinal plants O. compressa, N. procumbens, and S. surattense were found to be more effective than others and they retained HA titers at 0 after challenge. The next in order were extracts of O. esculentum, H. salicornicum and S. fruticosa which kept HA titers at 4, 8 and 16 respectively. The extracts of H. recurvum, P. antidotale, S. icolados and A. aspera were found less effective than above mentioned plant extracts and they kept the HA titers at 32, 64, 128 and 256 respectively. These results led us to conclude that the medicinal plants of Cholistan region are a rich source of antiviral agent(s) against AIV H9N2 and could be a source of cost effective alternate therapeutics.
Matched MeSH terms: Influenza in Birds/drug therapy; Influenza in Birds/virology
Highly pathogenic Avian Influenza (HPAI) virus is able to infect many hosts and the virus replicates in high levels in the respiratory tract inducing severe lung lesions. The pathogenesis of the disease is actually the outcome of the infection as determined by complex host-virus interactions involving the functional kinetics of large numbers of participating genes. Understanding the genes and proteins involved in host cellular responses are therefore, critical for the elucidation of the mechanisms of infection.
Matched MeSH terms: Influenza in Birds/immunology; Influenza in Birds/metabolism; Influenza in Birds/virology
A series of plasmids containing the HSP70 gene of Mycobacterium tuberculosis fused to the hemagglutinin (H5) gene of H5N1 avian influenza virus (AIV) (H5-HSP70 (heat shock protein 70) vaccine) or individual H5 gene (H5 vaccine) or HSP70 gene (HSP70 vaccine) were constructed based on the plasmid pcDNA3.1. Expression of H5 gene in Vero cells in vitro and in chickens in vivo was confirmed following their transfection and immunization with H5 or H5-HSP70 vaccines. Controls consisted of HSP70 vaccine, empty plasmid pcDNA3.1 and co-administered H5 and HSP70 vaccines. H5-HSP70 vaccine produced in chicken higher hemagglutination inhibition (HI) antibody titer than H5 vaccine. However, the increase was not statistically significant. We have demonstrated for the first time that the H5 DNA vaccine with fused HSP70 gene may produce an enhanced induction of humoral immune response to AIV in chickens.
Matched MeSH terms: Influenza in Birds/immunology; Influenza in Birds/prevention & control; Influenza in Birds/virology
Avian influenza viruses are highly infectious micro-organisms that primarily affect birds. Nevertheless, they have also been isolated from a number of mammals, including humans. Avian influenza virus can cause large economic losses to the poultry industry because of its high mortality. Although there are pathogenic variants with a low virulence and which generally cause only mild, if any, clinical symptoms, the subtypes H5 and H7 can mutate from a low to a highly virulent (pathogenic) virus and should be taken into consideration in eradication strategies. The primary source of infection for commercial poultry is direct and indirect contact with wild birds, with waterfowl forming a natural reservoir of the virus. Live-poultry markets, exotic birds, and ostriches also play a significant role in the epidemiology of avian influenza. The secondary transmission (i.e., between poultry farms) of avian influenza virus is attributed primarily to fomites and people. Airborne transmission is also important, and the virus can be spread by aerosol in humans. Diagnostic tests detect viral proteins and genes. Virus-specific antibodies can be traced by serological tests, with virus isolation and identification being complementary procedures. The number of outbreaks of avian influenza seems to be increasing - over the last 5 years outbreaks have been reported in Italy, Hong Kong, Chile, the Netherlands, South Korea, Vietnam, Japan, Thailand, Cambodia, Indonesia, Laos, China, Pakistan, United States of America, Canada, South Africa, and Malaysia. Moreover, a growing number of human cases of avian influenza, in some cases fatal, have paralleled the outbreaks in commercial poultry. There is great concern about the possibility that a new virus subtype with pandemic potential could emerge from these outbreaks. From the perspective of human health, it is essential to eradicate the virus from poultry; however, the large number of small-holdings with poultry, the lack of control experience and resources, and the international scale of transmission and infection make rapid control and long-term prevention of recurrence extremely difficult. In the Western world, the renewed interest in free-range housing carries a threat for future outbreaks. The growing ethical objections to the largescale culling of birds require a different approach to the eradication of avian influenza.
Matched MeSH terms: Influenza in Birds/epidemiology; Influenza in Birds/prevention & control*; Influenza in Birds/transmission
Numerous lessons have been learned so far in controlling H5N1 avian influenza in Asia. Early detection of incursions of virus prevented establishment of the disease in several countries, notably Japan, South Korea, and Malaysia. In countries where detection of early cases was delayed, infection is endemic and has been for three or more years. Control measures implemented in these countries need to reflect this finding. Vaccination will continue to be one of the key measures used in these endemically infected countries. Used alone, vaccination will not result in elimination of H5N1 viruses from a country, but, if used correctly, it will markedly reduce the prevalence of and susceptibility to infection. Vaccination has already played a valuable role in reducing the adverse effects of H5N1 viruses. Mass culling also reduces the level of infection in infected areas. However, the long-term benefits are limited in endemically infected countries owing to the high probability of reinfection on restocking unless other measures are used in parallel. Full epidemiological studies have not been conducted in many infected countries. Nevertheless, it is recognized that the number of clinical cases does not truly reflect the levels of infection. Domestic ducks and large live poultry markets have played a key role in the persistence of infection, because they can be infected silently. In tackling this disease, countries should adopt integrated control programs using the combination of measures best suited to the local environment. All surveillance data should be shared, both positive and negative, and should include information on cases of infection and disease. Socioeconomic and ecological implications of all control measures should be assessed before implementation, especially the impact on the rural poor.
Matched MeSH terms: Influenza in Birds/epidemiology*; Influenza in Birds/prevention & control; Influenza in Birds/virology*
Attenuated Salmonella has been used as a carrier for DNA vaccine. However, in vitro and in vivo studies on the bacteria following transfection of plasmid DNA were poorly studied. In this paper, eukaryotic expression plasmids encoding avian influenza virus (AIV) subtype H5N1 genes, pcDNA3.1/HA, NA, and NP, were transfected into an attenuated Salmonella enteric typhimurium SV4089. In vitro stability of the transfected plasmids into Salmonella were over 90% after 100 generations. The attenuated Salmonella were able to invade MCF-7 (1.2%) and MCF-10A (0.5%) human breast cancer cells. Newly hatched specific-pathogen-free (SPF) chicks were inoculated once by oral gavage with 10(9) colony-forming unit (CFU) of the attenuated Salmonella. No abnormal clinical signs or deaths were recorded after inoculation. Viable bacteria were detected 3 days after inoculation by plating from spleen, liver, and cecum. Fluorescent in situ hybridization (FISH) and polymerase chain reaction (PCR) were carried out for confirmation. Salmonella was not detected in blood cultures although serum antibody immune responses to Salmonella O antiserum group D1 factor 1, 9, and 12 antigens were observed in all the inoculated chickens after 7 days up to 35 days. Our results showed that live attenuated S. typhimurium SV4089 harboring pcDNA3.1/HA, NA, and NP may provide a unique alternative as a carrier for DNA oral vaccine in chickens.
Matched MeSH terms: Influenza in Birds/genetics; Influenza in Birds/immunology; Influenza in Birds/prevention & control*
A common approach for developing diagnostic tests for influenza virus detection is the use of mouse or rabbit monoclonal and/or polyclonal antibodies against a target antigen of the virus. However, comparative mapping of the target antigen using antibodies from different animal sources has not been evaluated before. This is important because identification of antigenic determinants of the target antigen in different species plays a central role to ensure the efficiency of a diagnostic test, such as competitive ELISA or immunohistochemistry-based tests. Interest in the matrix 2 ectodomain (M2e) protein of avian influenza virus (AIV) as a candidate for a universal vaccine and also as a marker for detection of virus infection in vaccinated animals (DIVA) is the rationale for the selection of this protein for comparative mapping evaluation. This study aimed to map the epitopes of the M2e protein of avian influenza virus H5N1 using chicken, mouse and rabbit monoclonal or monospecific antibodies. Our findings revealed that rabbit antibodies (rAbs) recognized epitope 6EVETPTRN13 of the M2e, located at the N-terminal of the protein, while mouse (mAb) and chicken antibodies (cAbs) recognized epitope 10PTRNEWECK18, located at the centre region of the protein. The findings highlighted the difference between the M2e antigenic determinants recognized by different species that emphasized the importance of comparative mapping of antibody reactivity from different animals to the same antigen, especially in the case of multi-host infectious agents such as influenza. The findings are of importance for antigenic mapping, as well as diagnostic test and vaccine development.
Vaccination is becoming a more acceptable option in the effort to eradicate avian influenza viruses (AIV) from commercial poultry, especially in countries where AIV is endemic. The main concern surrounding this option has been the inability of the conventional serological tests to differentiate antibodies produced due to vaccination from antibodies produced in response to virus infection. In attempts to address this issue, at least six strategies have been formulated, aiming to differentiate infected from vaccinated animals (DIVA), namely (i) sentinel birds, (ii) subunit vaccine, (iii) heterologous neuraminidase (NA), (iv) nonstructural 1 (NS1) protein, (v) matrix 2 ectodomain (M2e) protein, and (vi) haemagglutinin subunit 2 (HA2) glycoprotein. This short review briefly discusses the strengths and limitations of these DIVA strategies, together with the feasibility and practicality of the options as a part of the surveillance program directed toward the eventual eradication of AIV from poultry in countries where highly pathogenic avian influenza is endemic.
Matched MeSH terms: Influenza in Birds/immunology; Influenza in Birds/epidemiology; Influenza in Birds/prevention & control*; Influenza in Birds/virology
DNA vaccines offer several advantages over conventional vaccines in the development of effective vaccines against avian influenza virus (AIV). However, one of the limitations of the DNA vaccine in poultry is that it induces poor immune responses. In this study, chicken interleukin (IL) -15 and IL-18 were used as genetic adjuvants to improve the immune responses induced from the H5 DNA vaccination in chickens. The immunogenicity of the recombinant plasmid DNA was analyzed based on the antibody production, T cell responses and cytokine production, following inoculation in 1-day-old (Trial 1) and 14-day-old (Trial 2) specific-pathogen-free chickens. Hence, the purpose of the present study was to explore the role of chicken IL-15 and IL-18 as adjuvants following the vaccination of chickens with the H5 DNA vaccine.
Matched MeSH terms: Influenza in Birds/immunology; Influenza in Birds/prevention & control*
Subtype-specific multiplex reverse transcription-polymerase chain reaction (RT-PCR) was developed to simultaneously detect three subtypes (H5, H7 and H9) of avian influenza virus (AIV) type A. The sensitivity of the multiplex RT-PCR was evaluated and compared to that of RT-PCR-enzyme-linked immunosorbent assay (ELISA) and conventional RT-PCR. While the sensitivity of the multiplex RT-PCR is as sensitive as the conventional RT-PCR, it is 10 times less sensitive than RT-PCR-ELISA. The multiplex RT-PCR is also as sensitive as the virus isolation method in detecting H9N2 from tracheal samples collected at day 3 and 5 post inoculation. Hence, the developed multiplex RT-PCR assay is a rapid, sensitive and specific assay for detecting of AIV subtypes.
Matched MeSH terms: Influenza in Birds/diagnosis; Influenza in Birds/virology*
The transmission of highly pathogenic avian influenza H5N1 virus to Southeast Asian countries triggered the first major outbreak and transmission wave in late 2003, accelerating the pandemic threat to the world. Due to the lack of influenza surveillance prior to these outbreaks, the genetic diversity and the transmission pathways of H5N1 viruses from this period remain undefined. To determine the possible source of the wave 1 H5N1 viruses, we recently conducted further sequencing and analysis of samples collected in live-poultry markets from Guangdong, Hunan, and Yunnan in southern China from 2001 to 2004. Phylogenetic analysis of the hemagglutinin and neuraminidase genes of 73 H5N1 isolates from this period revealed a greater genetic diversity in southern China than previously reported. Moreover, results show that eight viruses isolated from Yunnan in 2002 and 2003 were most closely related to the clade 1 virus sublineage from Vietnam, Thailand, and Malaysia, while two viruses from Hunan in 2002 and 2003 were most closely related to viruses from Indonesia (clade 2.1). Further phylogenetic analyses of the six internal genes showed that all 10 of those viruses maintained similar phylogenetic relationships as the surface genes. The 10 progenitor viruses were genotype Z and shared high similarity (>/=99%) with their corresponding descendant viruses in most gene segments. These results suggest a direct transmission link for H5N1 viruses between Yunnan and Vietnam and also between Hunan and Indonesia during 2002 and 2003. Poultry trade may be responsible for virus introduction to Vietnam, while the transmission route from Hunan to Indonesia remains unclear.
Matched MeSH terms: Influenza in Birds/epidemiology; Influenza in Birds/virology*
Graphene/zinc oxide nanocomposite was synthesised via a facile, green and efficient approach consisted of novel liquid phase exfoliation and solvothermal growth for sensing application. Highly pristine graphene was synthesised through mild sonication treatment of graphite in a mixture of ethanol and water at an optimum ratio. The X-ray diffractometry (XRD) affirmed the hydrothermal growth of pure zinc oxide nanoparticles from zinc nitrate hexahydrate precursor. The as-prepared graphene/zinc oxide (G/ZnO) nanocomposite was characterised comprehensively to evaluate its morphology, crystallinity, composition and purity. All results clearly indicate that zinc oxide particles were homogenously distributed on graphene sheets, without any severe aggregation. The electrochemical performance of graphene/zinc oxide nanocomposite-modified screen-printed carbon electrode (SPCE) was evaluated using cyclic voltammetry (CV) and amperometry analysis. The resulting electrode exhibited excellent electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2) in a linear range of 1-15 mM with a correlation coefficient of 0.9977. The sensitivity of the graphene/zinc oxide nanocomposite-modified hydrogen peroxide sensor was 3.2580 μAmM(-1) with a limit of detection of 7.4357 μM. An electrochemical DNA sensor platform was then fabricated for the detection of Avian Influenza H5 gene based on graphene/zinc oxide nanocomposite. The results obtained from amperometry study indicate that the graphene/zinc oxide nanocomposite-enhanced electrochemical DNA biosensor is significantly more sensitive (P
DNA formulations provide the basis for safe and cost effective vaccine. Low efficiency is often observed in the delivery of DNA vaccines. In order to assess a new strategy for oral DNA vaccine formulation and delivery, plasmid encoding hemagglutinin (HA) gene of avian influenza virus, A/Ck/Malaysia/5858/04 (H5N1) (pcDNA3.1/H5) was formulated using green synthesis of sliver nanoparticles (AgNP) with polyethylene glycol (PEG). AgNP were successfully synthesized uniformly dispersed with size in the range of 4 to 18 nm with an average size of 11 nm. Cytotoxicity of the prepared AgNP was investigated in vitro and in vivo using MCF-7 cells and cytokine expression, respectively. At the concentration of -5 log₁₀AgNP, no cytotoxic effects were detected in MCF-7 cells with 9.5% cell death compared to the control. One-day-old specific pathogen-free (SPF) chicks immunized once by oral gavage with 10 μl of pcDNA3.1/H5 (200 ng/ml) nanoencapsulated with 40 μl AgNP (3.7×10⁻² μg of Ag) showed no clinical manifestations. PCR successfully detect the AgNP/H5 plasmid from the duodenum of the inoculated chicken as early as 1h post-immunization. Immunization of chickens with AgNP/H5 enhanced both pro inflammatory and Th1-like expressions, although no significant differences were recorded in the chickens inoculated with AgNP, AgNP/pcDNA3.1 and the control. In addition, serum samples collected from immunized chickens with AgNP/H5 showed rapidly increasing antibody against H5 on day 14 after immunization. The highest average antibody titres were detected on day 35 post-immunization at 51.2±7.5. AgNP/H5 also elicited both CD4+ and CD8+ T cells in the immunized chickens as early as day 14 after immunization, at 7.5±2.0 and 20±1.9 percentage, respectively. Hence, single oral administrations of AgNP/H5 led to induce both the antibody and cell-mediated immune responses as well as enhanced cytokine production.
Matched MeSH terms: Influenza in Birds/genetics; Influenza in Birds/immunology; Influenza in Birds/prevention & control*