HPAI H5N1 Research Articles

Estimating the between-farm transmission rates for highly pathogenic avian influenza subtype H5N1 epidemics in Bangladesh between 2007 and 2013.

Highly Pathogenic Avian Influenza (HPAI) is classified by the World Organization for Animal Health as one of the notifiable diseases. Its occurrence is associated with severe socio-economic impacts and is also zoonotic. Bangladesh HPAI epidemic data for the period between 2007 and 2013 were obtained and split into epidemic waves based on the time lag between outbreaks. By assuming the number of newly infected farms to be binomially distributed, we fit a Generalized Linear Model to the data to estimate between-farm transmission rates (β). These parameters are then used together with the calculated infectious periods to estimate the respective basic reproduction numbers (R0 ). The change in β and R0 with time during the course of each epidemic wave was explored. Finally, sensitivity analyses of the effects of reducing the delay in detecting infection on a farm as well as extended infectiousness of a farm beyond the day of culling were assessed. The point estimates obtained for β ranged from 0.08 (95% CI: 0.06-0.10) to 0.11 (95% CI: 0.08-0.20) per infectious farm per day while R0 ranged from 0.85 (95% CI: 0.77-1.02) to 0.96 (95% CI: 0.72-1.20). Sensitivity analyses reveal that the estimates are quite robust to changes in the assumptions about the day in reporting infection and extended infectiousness. In the analysis allowing for time-varying transmission parameters, the rising and declining phases observed in the epidemic data were synchronized with the moments when R0 was greater and less than one, respectively. From an epidemiological perspective, the consistency of these estimates and their magnitude (R0 ≈1) indicate that the effectiveness of the deployed control measures was largely invariant between epidemic waves and the trend of the time-varying R0 supports the hypothesis of sustained farm-to-farm transmission that is possibly initiated by a few unique introductions.

From Variation of Influenza Viral Proteins to Vaccine Development.

Recurrent influenza epidemics and occasional pandemics are one of the most important global public health concerns and are major causes of human morbidity and mortality. Influenza viruses can evolve through antigen drift and shift to overcome the barriers of human immunity, leading to host adaption and transmission. Mechanisms underlying this viral evolution are gradually being elucidated. Vaccination is an effective method for the prevention of influenza virus infection. However, the emergence of novel viruses, including the 2009 pandemic influenza A (H1N1), the avian influenza A virus (H7N9), and the highly pathogenic avian influenza A virus (HPAI H5N1), that have infected human populations frequently in recent years reveals the tremendous challenges to the current influenza vaccine strategy. A better vaccine that provides protection against a wide spectrum of various influenza viruses and long-lasting immunity is urgently required. Here, we review the evolutionary changes of several important influenza proteins and the influence of these changes on viral antigenicity, host adaption, and viral pathogenicity. Furthermore, we discuss the development of a potent universal influenza vaccine based on this knowledge.

Efficacy of an inactivated bivalent vaccine against the prevalent strains of Newcastle disease and H9N2 avian influenza

BackgroundNewcastle disease (ND) and avian influenza subtype H9N2 (H9N2 AI) are two of the most important diseases of poultry, causing severe economic losses in the global poultry industry. Vaccination is an effective way to prevent and control the spread of ND virus (NDV) and H9N2 AI virus (AIV), but the antigenic differences between the current circulating strains and the vaccine strains might account for recent ND and H9N2 AI outbreaks in vaccinated poultry flocks.MethodsWe developed an inactivated bivalent H9N2 and NDV vaccine based on the current prevalent strains of H9N2 AIV and NDV in China and evaluated its efficacy in chickens in this study.ResultsThe results indicated that the inactivated bivalent vaccine could induce a fast antibody response in vaccinated chickens. The hemagglutination inhibition (HI) titer in the sera increased rapidly, and the highest HI titer was observed at 4 weeks post-vaccination (wpv) with a mean titre of 8.6 log2 for NDV and 9.5 log2 for H9N2. Up until 15 wpv, HI titers were still detectable at a high level of over 6 log2. The immunized chickens showed no signs of disease after challenge at 3 wpv with the prevalent strains of NDV and H9N2 AIV isolated in 2012–2014. Moreover, viral shedding was completely inhibited in vaccinated chickens after challenge with H9N2 AIV and inhibited by at least 90% with NDV compared to the controls at 5dpc.ConclusionsOur findings suggest that the inactivated NDV and H9N2 vaccine induces a fast and strong antibody response in vaccinated chickens and is efficacious in poultry against NDVs and H9N2 AIVs.

Isolation and genetic characterization of a novel 2.2.1.2a H5N1 virus from a vaccinated meat-turkeys flock in Egypt

BackgroundVaccination of poultry to control highly pathogenic avian influenza virus (HPAIV) H5N1 is used in several countries. HPAIV H5N1 of clade 2.2.1 which is endemic in Egypt has diversified into two genetic clades. Clade 2.2.1.1 represents antigenic drift variants in vaccinated commercial poultry while clade 2.2.1.2 variants are detected in humans and backyard poultry. Little is known about H5N1 infection in vaccinated turkeys under field conditions.Case presentationHere, we describe an HPAI H5N1 outbreak in a vaccinated meat-turkey flock in Egypt. Birds were vaccinated with inactivated H5N2 and H5N1 vaccines at 8 and 34 days of age, respectively. At 72nd day of age (38 days post last vaccination), turkeys exhibited mild respiratory signs, cyanosis of snood and severe congestion of the internal organs. Survivors had a reduction in feed consumption and body gain. A mortality of ~29% cumulated within 10 days after the onset of clinical signs. Laboratory diagnosis using RT-qPCRs revealed presence of H5N1 but was negative for H7 and H9 subtypes. A substantial antigenic drift against different serum samples from clade 2.2.1.1 and clade 2.3.4.4 was observed. Based on full genome sequence analysis the virus belonged to clade 2.2.1.2 but clustered with recent H5N1 viruses from 2015 in poultry in Israel, Gaza and Egypt in a novel subclade designated here 2.2.1.2a which is distinct from 2014/2015 2.2.1.2 viruses. These viruses possess 2.2.1.2 clade-specific genetic signatures and also mutations in the HA similar to those in clade 2.2.1.1 that enabled evasion from humoral immune response. Taken together, this manuscript describes a recent HPAI H5N1 outbreak in vaccinated meat-turkeys in Egypt after infection with a virus representing novel distinct 2.2.1.2a subclade.ConclusionsInfection with HPAIV H5N1 in commercial turkeys resulted in significant morbidity and mortality despite of vaccination using H5 vaccines. The isolated virus showed antigenic drift and clustered in a novel cluster designated here 2.2.1.2a related to viruses in poultry in Israel, Gaza and Egypt. Enforcement of biosecurity and constant update of vaccine virus strains may be helpful to protect vaccinated birds and prevent spillover infection to neighbouring countries.

Co-infection of H9N2 subtype avian influenza virus and infectious bronchitis virus decreases SP-A expression level in chickens

Chicken surfactant protein A (cSP-A) is a collectin believed to play an important role in antiviral immunity. However, cSP-A expression in the respiratory tract of chickens after viral co-infection remains unclear. The aim of this study was the detection and characterization of cSP-A in co-infected chickens. For this purpose, four-week-old specific pathogen-free (SPF) chickens were divided into five groups and inoculated intranasally with H9N2 subtype avian influenza virus (AIV), infectious bronchitis virus (IBV), or Newcastle disease virus (NDV). Chickens were sacrificed at three days post inoculation, and the lung, trachea, and air sac samples were taken to determine histological changes and expression levels of cSP-A mRNA and cSP-A protein. The cSP-A mRNA and its protein were detected separately using real-time quantitative reverse transcriptional polymerase chain reaction (qRT-PCR), a sandwich enzyme-linked immunosorbent assay (S-ELISA), and an immunohistochemistry assay (IHC). In comparison, for the PBS group as the negative group and the NDV-infected group as the positive group, the histological changes showed that the lesions of the AIV+ IBV co-infected group were more serious compared to the AIV-infected group and the IBV-infected group. Consequently, the expression level of cSP-A in the AIV+IBV co-infected group significantly decreased when compared to the AIV-infected group and the IBV-infected group by qRT-PCR, ELISA, and IHC analysis. The mechanism of the downregulation of SP-A expression level will be addressed in future.

Optimizing the process of inactivating influenza virus subtype H9N2 by formalin in the production of killed avian influenza vaccine

Avian influenza is one of the most important diseases in avian industry, which also threats human population. Thus, vaccination is necessary for controlling this viral disease. In this study, killed vaccine of avian influenza subtype H9N2 and formalin solution (for virus inactivation) were used. It is necessary to study the effect of different factors such as formalin concentration, as well as incubation temperature and duration on inactivation process. For this purpose, after preparation and measurement of antibody titers of vaccinal strains of avian influenza, 27 experimental samples of H9N2 avian influenza virus were prepared at different formalin concentrations (0.1%, 0.05%, and 0.025%), at different incubation temperatures (4 °C, 25 °C, and 37 °C), and in different incubation durations (12, 18, and 24 h). In addition, three control samples were prepared at three different test temperatures without adding formalin. All the samples were evaluated by inactivation test, hemagglutination assay, and measurement of free formaldehyde. All the experiments were repeated within three consecutive periods. Considering the findings and destructive effects of long incubation durations at 37°C on antigens, the temperature of 25 °C was more suitable. Furthermore, the free formaldehyde amounts at different concentrations at 25 °C were slightly different in comparison with 37 °C. Therefore, formalin concentration of 0.1% at 25 °C completely inactivated the virus within 24 h and was proposed as the optimal condition.

A novel hemagglutinin protein produced in bacteria protects chickens against H5N1 highly pathogenic avian influenza viruses by inducing H5 subtype-specific neutralizing antibodies.

The highly pathogenic (HP) H5N1 avian influenza viruses (AIVs) cause a mortality rate of up to 100% in infected chickens and pose a permanent pandemic threat. Attempts to obtain effective vaccines against H5N1 HPAIVs have focused on hemagglutinin (HA), an immunodominant viral antigen capable of eliciting neutralizing antibodies. The vast majority of vaccine projects have been performed using eukaryotic expression systems. In contrast, we used a bacterial expression system to produce vaccine HA protein (bacterial HA) according to our own design. The HA protein with the sequence of the H5N1 HPAIV strain was efficiently expressed in Escherichia coli, recovered in the form of inclusion bodies and refolded by dilution between two chromatographic purification steps. Antigenicity studies showed that the resulting antigen, referred to as rH5-E. coli, preserves conformational epitopes targeted by antibodies specific for H5-subtype HAs, inhibiting hemagglutination and/or neutralizing influenza viruses in vitro. The proper conformation of this protein and its ability to form functional oligomers were confirmed by a hemagglutination test. Consistent with the biochemical characteristics, prime-boost immunizations with adjuvanted rH5-E. coli protected 100% and 70% of specific pathogen-free, layer-type chickens against challenge with homologous and heterologous H5N1 HPAIVs, respectively. The observed protection was related to the positivity in the FluAC H5 test (IDVet) but not to hemagglutination-inhibiting antibody titers. Due to full protection, the effective contact transmission of the homologous challenge virus did not occur. Survivors from both challenges did not or only transiently shed the viruses, as established by viral RNA detection in oropharyngeal and cloacal swabs. Our results demonstrate that vaccination with rH5-E. coli could confer control of H5N1 HPAIV infection and transmission rates in chicken flocks, accompanied by reduced virus shedding. Moreover, the role of H5 subtype-specific neutralizing antibodies in anti-influenza immunity and a novel correlate of protection are indicated.

Genetic and antigenic evolution of H9N2 subtype avian influenza virus in domestic chickens in southwestern China, 2013-2016.

H9N2 avian influenza virus (AIV) has caused significant losses in chicken flocks throughout china in recent years. There is a limited understanding of the genetic and antigenic characteristics of the H9N2 virus isolated in chickens in southwestern China. In this study a total of 12 field strains were isolated from tissue samples from diseased chickens between 2013 and 2016. Phylogenetic analysis of the Hemagglutinin (HA) and Neuraminidase (NA) nucleotide sequences from the 12 field isolates and other reference strains showed that most of the isolates in the past four years could be clustered into a major branch (HA-branch A and NA-branch I) in the Clade h9.4.2 lineages. These sequences are accompanied by nine and seven new amino acids mutations in the HA and NA proteins, respectively, when compared with those previous to 2013. In addition, four new isolates were grouped into a minor branch (HA-branch B) in the Clade h9.4.2 lineages and two potential N-glycosylation sites were observed due to amino acid mutations in the HA protein. Three antigenic groups (1–3), which had low antigenic relatedness with two commonly used vaccines in China, were identified among the 12 isolates by antigenMap analysis. Immunoprotection testing showed that those two vaccines could efficiently prevent the shedding of branch A viruses but not branch B viruses. In conclusion, these results indicate the genotype of branch B may become epidemic in the next few years and that a new vaccine should be developed for the prevention of H9N2 AIV.

Evaluation of the Protective Efficacy of Poly I:C as an Adjuvant for H9N2 Subtype Avian Influenza Inactivated Vaccine and Its Mechanism of Action in Ducks.

Current commercial H9 avian influenza vaccines cannot provide satisfactory protective immunity against antigenic variant influenza viruses in ducks. Poly I:C, when used as an adjuvant, improves humoral and cellular immunity in many animals but has not been tested in ducks. In this study, we investigated the protective efficacy of Poly I:C as an adjuvant for an inactivated H9N2 Avian influenza vaccine in ducks. We found that an H9N2 vaccine administered with poly I:C (H9-PIC vaccine) induced a significantly more rapid response with higher anti-influenza antibody titers than those of the vaccine alone (H9 vaccine). Moreover, virus shedding was reduced in ducks immunized with the H9-PIC vaccine after challenge with an H9 subtype antigenic variant viruses. IFN-α, IFN-γ, IL-6 and MHC-II mRNA levels were all elevated in ducks receiving the H9-PIC vaccine. In addition, lower expression level of MHC-I may be a reason for inefficient protective ability against heterologous influenza viruses in H9-PIC vaccination of ducks. In conclusion, poly I:C adjuvant enhanced both humoral and cellular immune responses in ducks induced by immunization of inactivated H9N2 vaccine.

Purification and immunogenicity of hemagglutinin from highly pathogenic avian influenza virus H5N1 expressed in Nicotiana benthamiana

ABSTRACTHighly pathogenic avian influenza (HPAI) H5N1 is an ongoing global health concern due to its severe sporadic outbreaks in Asia, Africa and Europe, which poses a potential pandemic threat. The development of safe and cost-effective vaccine candidates for HPAI is considered the best strategy for managing the disease and addressing the pandemic preparedness. The most potential vaccine candidate is the antigenic determinant of influenza A virus, hemagglutinin (HA). The present research was aimed at developing optimized expression in Nicotiana benthamiana and protein purification process for HA from the Malaysian isolate of H5N1 as a vaccine antigen for HPAI H5N1. Expression of HA from the Malaysian isolate of HPAI in N. benthamiana was confirmed, and more soluble protein was expressed as truncated HA, the HA1 domain over the entire ectodomain of HA. Two different purification processes were evaluated for efficiency in terms of purity and yield. Due to the reduced yield, protein degradation and length of the 3-column purification process, the 2-column method was chosen for target purification. Purified HA1 was found immunogenic in mice inducing H5 HA-specific IgG and a hemagglutination inhibition antibody. This paper offers an alternative production system of a vaccine candidate against a locally circulating HPAI, which has a regional significance.

Global early warning signs for health threats at the human animal ecosystem interface

Diseases are emerging and remerging rapidly in different ecosystems and regions. Disease surveillance is an approach widely used for detecting new pathogens through event-based or indicator surveillance efforts. We should ask ourselves why, as a global community, do we not implement a robust global surveillance and early warning system capable of detecting early signals of disease emergence? In addition, why is it that we continue to incur high costs of crisis mitigation, as in outbreaks of H5N1 HPAI, Nipah, MERS-CoV, Zika, Ebola, etc., particularly in regions associated with poor indicators of development and high vulnerability?

Sensitization with vaccinia virus encoding H5N1 hemagglutinin restores immune potential against H5N1 influenza virus.

H5N1 highly pathogenic avian influenza (H5N1 HPAI) virus causes elevated mortality compared with seasonal influenza viruses like H1N1 pandemic influenza (H1N1 pdm) virus. We identified a mechanism associated with the severe symptoms seen with H5N1 HPAI virus infection. H5N1 HPAI virus infection induced a decrease of dendritic cell number in the splenic extrafollicular T-cell zone and impaired formation of the outer layers of B-cell follicles, resulting in insufficient levels of antibody production after infection. However, in animals vaccinated with a live recombinant vaccinia virus expressing the H5 hemagglutinin, infection with H5N1 HPAI virus induced parafollicular dendritic cell accumulation and efficient antibody production. These results indicate that a recombinant vaccinia encoding H5 hemagglutinin gene does not impair dendritic cell recruitment and can be a useful vaccine candidate.

The Effect of Tsukamurella inchonensis Bacterin on the Immune Response Against Influenza and Newcastle Disease Vaccines in Broiler Chickens

Background: In poultry production, improving immunity is very important to prevent infectious diseases. One solution to improve the immunity of animals and to decrease their susceptibility to infectious disease is administration of immunostimulants. Surveys have indicated that some bacteria can work as immunomodulators such as Mycobacterium vaccae and can promote Th1-mediated mechanisms, and switch off pre-existing Th2 preponderance (1). Objectives: The aim of this study was to examine the effect of Tsukamurella inchonensis bacterin on the immune response against Influenza and Newcastle disease vaccine in broiler chickens . Materials and Methods: A total of 170 day-old broiler chicks were purchased and divided randomly into 5 equal groups. Chickens of group A received 106 bacterin subcutaneously on two days before vaccination against Newcastle disease and avian influenza. Chickens of group B received 106 bacterin subcutaneously on six days after the first injection of bacterin. Chickens of group C received 106bacterin subcutaneously on six days after the second injection of bacterin. Chickens of group D, vaccinated against Newcastle disease and avian influenza but did not receive bacterin. Chickens of group E, did not vaccinate against Newcastle disease and avian influenza and did not receive bacterin. All groups except group E, were vaccinated with live Newcastle vaccine and AI-ND killed vaccine (subtype H9N2). Blood samples were collected and antibody titer against Newcastle disease vaccine and avian influenza vaccine was determined by HI test. Results: The results of present study showed that receiving of Tsukamurella inchonensis bacterin for 3 times, significantly increased the specific antibody response to avian influenza subtype H9N2 vaccine. Also about Newcastle vaccine, significantly increased the specific antibody response to Newcastle vaccine at 21 and 28 days after vaccination. Conclusions: Receiving of Tsukamurella inchonensis bacterin can enhance immune response against NDV and AIV.

In vitro exposure system for study of aerosolized influenza virus

Infection of adherent cell monolayers using a liquid inoculum represents an established method to reliably and quantitatively study virus infection, but poorly recapitulates the exposure and infection of cells in the respiratory tract that occurs during infection with aerosolized pathogens. To better simulate natural infection in vitro, we adapted a system that generates viral aerosols similar to those exhaled by infected humans to the inoculation of epithelial cell monolayers. Procedures for cellular infection and calculation of exposure dose were developed and tested using viruses characterized by distinct transmission and pathogenicity phenotypes: an HPAI H5N1, an LPAI H7N9, and a seasonal H3N2 virus. While all three aerosolized viruses were highly infectious in a human bronchial epithelial cell line (Calu-3) cultured submerged in media, differences between the viruses were observed in primary human alveolar epithelial cells and in Calu-3 cells cultured at air-liquid interface. This system provides a novel enhancement to traditional in vitro experiments, particularly those focused on the early stages of infection.

The NS1 protein of avian influenza virus H9N2 induces oxidative-stress-mediated chicken oviduct epithelial cells apoptosis.

The pathogenesis of H9N2 subtype avian influenza virus infection (AIV) in hens is often related to oviduct tissue damage. The viral non-structural NS1 protein is thought to play a key role in regulating the pathogenicity of AIV, but its exact function in this process remains elusive. In this study, the pro-apoptosis effect of H9N2 NS1 protein was examined on chicken oviduct epithelial cells (COECs) and our data indicated that NS1-induced oxidative stress was a contributing factor in apoptosis. Our data indicate that NS1 protein level was correlated with reactive oxygen species (ROS) in COECs transfected with NS1 expression plasmids. Interestingly, decreased activities of antioxidant enzymes, superoxide dismutase and catalase, were observed in NS1-transfected COECs. Treatment of COECs with antioxidants, such as pyrrolidine dithiocarbamate (PDTC) or N-acetylcysteine (NAC), significantly inhibited NS1-induced apoptosis. Moreover, although antioxidant treatment has little effect on the activation of caspase-8 in NS1-transfected cells, the activation of caspase-3/9 and Bax/Bcl-2 were significantly downregulated. Taken together, the results of our study demonstrated that expression of H9N2 NS1 alone is sufficient to trigger oxidative stress in COECs. Additionally, NS1 protein can induce cellular apoptosis via activating ROS accumulation and mitochondria-mediated apoptotic signalling in COECs.

An evaluation of biosecurity compliance levels and assessment of associated risk factors for highly pathogenic avian influenza H5N1 infection of live-bird-markets, Nigeria and Egypt

Live bird market (LBM) is integral component in the perpetuation of HPAI H5N1, while biosecurity is crucial and key to the prevention and control of infectious diseases. Biosecurity compliance level and risk factor assessments in 155LBMs was evaluated in Nigeria and Egypt through the administration of a 68-item biosecurity checklist, scored based on the modifications of previous qualitative data, and analysed for degree of compliance. LBMs were scored as “complied with a biosecurity item” if they had good-very good scores (4). All scores were coded and analysed using descriptive statistics and risk or protective factors were determined using univariable and multivariable logistic regression at p≤0.05. Trading of wild birds and other animal in the LBMs (Odd Ratio (OR)=34.90; p=0.01) and claims of hand disinfection after slaughter (OR=31.16; p=0.03) were significant risk factors while mandatory routine disinfection of markets (OR=0.13; p≤0.00), fencing and gates for live bird market (OR=0.02; p≤0.01) and hand washing after slaughter (OR=0.41; p≤0.05) were protective factors for and against the infection of Nigerian and Egyptian LBMs with the HPAI H5N1 virus. Almost all the LBMs complied poorly with most of the variables in the checklist (p≤0.05), but pathways to improved biosecurity in the LBMs existed. We concluded that the LBM operators play a critical role in the disruption of transmission of H5N1 virus infection through improved biosecurity and participatory epidemiology and multidisciplinary approach is needed.

Time-space analysis of highly pathogenic avian influenza H5N2 outbreak in the US.

BackgroundIn early 2015, highly pathogenic avian influenza H5N2 caused outbreaks in commercial poultry farms in Minnesota and neighboring states where more than 48 million birds were affected. To date, the origin and transmission pathways of HPAI H5N2 have not been conclusively established.MethodsIn this study, we analyzed forty-six samples from turkeys and their environment that were collected at different time-points of the outbreak to identify origins and within outbreak evolutionary changes. We performed de-novo whole genome sequencing from primary samples and the most recent common ancestors of the PB2, PA, HA5, M and NS segments were traced back to Japanese HPAI H5N8 isolates. These segments appeared to have diverged from the ancestor around June and November 2014.ResultsThe time to most recent common ancestor analysis for PB1, NP and NA2 segments suggest two likely possibilities of reassortant HPAI H5N2 origin - either a reassortment in Alaska area or multiple reassortments with North American low pathogenic avian influenza strains, before the HPAI H5N2 outbreak strain emerged. Within the outbreak, viruses clustered into two and three subgroups suggesting high substitution rates of 0.702x10-2 - 1.665x10-2 (subs/site/year), over the 5-month outbreak period.ConclusionsData are suggestive of a fast evolving HPAI strain within an outbreak that should be taken into consideration in developing appropriate control strategies in the future.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-016-0605-4) contains supplementary material, which is available to authorized users.

Cross-protective efficacies of highly-pathogenic avian influenza H5N1 vaccines against a recent H5N8 virus

To investigate cross-protective vaccine efficacy of highly-pathogenic avian influenza H5N1 viruses against a recent HPAI H5N8 virus, we immunized C57BL/6 mice and ferrets with three alum-adjuvanted inactivated whole H5N1 vaccines developed through reverse-genetics (Rg): [Vietnam/1194/04xPR8 (clade 1), Korea/W149/06xPR8 (clade 2.2), and Korea/ES223N/03xPR8 (clade 2.5)]. Although relatively low cross-reactivities (10–40 HI titer) were observed against heterologous H5N8 virus, immunized animals were 100% protected from challenge with the 20 mLD50 of H5N8 virus, with the exception of mice vaccinated with 3.5μg of Rg Vietnam/1194/04xPR8. Of note, the Rg Korea/ES223N/03xPR8 vaccine provided not only effective protection, but also markedly inhibited viral replication in the lungs and nasal swabs of vaccine recipients within five days of HPAI H5N8 virus challenge. Further, we demonstrated that antibody-dependent cell-mediated cytotoxicity (ADCC) of an antibody-coated target cell by cytotoxic effector cells also plays a role in the heterologous protection of H5N1 vaccines against H5N8 challenge.

Southward autumn migration of waterfowl facilitates cross-continental transmission of the highly pathogenic avian influenza H5N1 virus.

The highly pathogenic avian influenza subtype H5N1 (HPAI H5N1) is a worldwide zoonotic infectious disease, threatening humans, poultry and wild birds. The role of wild birds in the spread of HPAI H5N1 has previously been investigated by comparing disease spread patterns with bird migration routes. However, the different roles that the southward autumn and northward spring migration might play in virus transmission have hardly been explored. Using direction analysis, we analyze HPAI H5N1 transmission directions and angular concentration of currently circulating viral clades, and compare these with waterfowl seasonal migration directions along major waterfowl flyways. Out of 22 HPAI H5N1 transmission directions, 18 had both a southward direction and a relatively high concentration. Differences between disease transmission and waterfowl migration directions were significantly smaller for autumn than for spring migration. The four northward transmission directions were found along Asian flyways, where the initial epicenter of the virus was located. We suggest waterfowl first picked up the virus from East Asia, then brought it to the north via spring migration, and then spread it to other parts of world mainly by autumn migration. We emphasize waterfowl autumn migration plays a relatively important role in HPAI H5N1 transmission compared to spring migration.

Quantitative assessment of a spatial multicriteria model for highly pathogenic avian influenza H5N1 in Thailand, and application in Cambodia.

The Highly Pathogenic Avian Influenza H5N1 (HPAI) virus is now considered endemic in several Asian countries. In Cambodia, the virus has been circulating in the poultry population since 2004, with a dramatic effect on farmers’ livelihoods and public health. In Thailand, surveillance and control are still important to prevent any new H5N1 incursion. Risk mapping can contribute effectively to disease surveillance and control systems, but is a very challenging task in the absence of reliable disease data. In this work, we used spatial multicriteria decision analysis (MCDA) to produce risk maps for HPAI H5N1 in poultry. We aimed to i) evaluate the performance of the MCDA approach to predict areas suitable for H5N1 based on a dataset from Thailand, comparing the predictive capacities of two sources of a priori knowledge (literature and experts), and ii) apply the best method to produce a risk map for H5N1 in poultry in Cambodia. Our results showed that the expert-based model had a very high predictive capacity in Thailand (AUC = 0.97). Applied in Cambodia, MCDA mapping made it possible to identify hotspots suitable for HPAI H5N1 in the Tonlé Sap watershed, around the cities of Battambang and Kampong Cham, and along the Vietnamese border.