Transmission Of Avian Influenza Research Articles

The Probability of Highly Pathogenic Avian Influenza Introduction and Transmission in Western Java Poultry Chains: Linking Value Chains and Expert Estimates

The Probability of Highly Pathogenic Avian Influenza Introduction and Transmission in Western Java Poultry Chains: Linking Value Chains and Expert Estimates

Prevalence of HPAI in passerines, woodpeckers and doves presented to the Center for Wild Bird Rehabilitation during the 2022 HPAI H5N1 epizootic

The Highly Pathogenic Avian Influenza (HPAI) H5N1 clade 2.3.4.4b epizootic affecting North America beginning in late 2021 has affected wild and domestic birds to an unprecedented scale. Mortalities have been documented mainly in raptors, aquatic birds (shorebirds, waterfowl), gulls and other scavenging birds, with rare reports of other species being affected. Passerines, woodpeckers, and doves are not thought to contribute significantly to the transmission of avian influenza, and thus are not regularly tested. Despite this, mortalities and even the possibility of asymptomatic carrier states in songbirds have been documented with HPAI H5N1 strains. This study focused on sampling and testing of species not typically included in HPAI surveillance, to help assess prevalence, symptoms of infection if detected and the possibility of asymptomatic carriers. Throughout two periods in 2022, 164 individuals of 38 species were sampled from Vermont and New Hampshire. None of these birds tested positive for any strain of avian influenza virus. While the scale of this study is small, it highlights the need for testing species that are not a part of regular HPAI surveillance, as well as the role rehabilitation centers may play in that goal.

Effect of avian influenza scare on transmission of zoonotic avian influenza: A case study of influenza A (H7N9)

Avian influenza scare is a human psychological factor that asserts both positive and negative effects on the transmission of zoonotic avian influenza. In order to study the dichotomous effect of avian influenza scare on disease transmission, taking H7N9 avian influenza as a typical case, a two-patch epidemic model is proposed. The global dynamics and the threshold criteria are established by LaSalle invariant principle and the theory of asymptotic autonomous system. To mitigate the negative effects and curb illegal poultry trade, a game-theoretic model is adopted to explore the optimal policy of culling subsidies to reasonably compensate stakeholders for their economic losses resulting from the scare. The optimal policy of culling subsidy is found to heavily depend on the penalty of illegal poultry trade, the stakeholders’ income, the intensity of control measures, and the prevalence level of the disease. The negative effect of avian influenza scare on disease transmission is considerably more significant than the positive effect. In order to avoid a widespread outbreak of zoonotic avian influenza across the region, a comprehensive national global control strategy is essential and effective, even in the presence of the negative effect of the avian influenza scare.

Serosurvey for H5, H7 and H9 avian influenza viruses in local chickens in live bird markets within Kaduna metropolis, Nigeria

Since the first 2006 Avian Influenza (AI) outbreak in Nigeria, it has continued to circulate and ravage the poultry industry with huge economic losses above 130 billion naira. Local poultry are important sources of AI transmission and maintenance of the highly pathogenic avian influenza H5N1. Live bird markets (LBMs) are “breeding grounds” and major risk factors for human infection of AI. The seroprevalence of AI in local chickens in LBMs in Kaduna Metropolis, Nigeria was determined. Sera were obtained from the local chickens (n=300) in 5 daily LBMs and subjected to competitive enzyme-linked immunosorbent assay (c-ELISA) to detect the nucleoprotein antibodies. The c-ELISA positive samples were further screened by haemagglutination inhibition (HI) test for AI using H5, H7 and H9 antigens. The overall AI seroprevalence was 1.7 % with the highest individual seroprevalence of 3.3% in Kawo and Railway LBMs. There was no statistically significant association between the location of LBMs and AI presence, and between the sex and presence of AI antibodies (p = 0.427). One sample was HI positive for antibodies against H5, H7 and H9 with mean titers of 4, 2.5 and 3.5 log2, respectively. This implies the potential danger of the spread of AI among humans and animals. There should be sustained surveillance and biosecurity in the live bird market.

Influenza A Virus in Pigs in Senegal and Risk Assessment of Avian Influenza Virus (AIV) Emergence and Transmission to Human.

We conducted an active influenza surveillance in the single pig slaughterhouse in Dakar to investigate the epidemiology and genetic characteristics of influenza A viruses (IAVs) and to provide serologic evidence of avian influenza virus (AIV) infection in pigs at interfaces with human populations in Senegal. Nasal swab and blood samples were collected on a weekly basis from the same animal immediately after slaughter. Influenza A viruses were diagnosed using RT-qPCR and a subset of positive samples for H3 and H1 subtypes were selected for full genome amplification and NGS sequencing. Serum samples were tested by HI assay for the detection of antibodies recognizing four AIVs, including H9N2, H5N1, H7N7 and H5N2. Between September 2018 and December 2019, 1691 swine nasal swabs were collected and tested. Influenza A virus was detected in 30.7% (520/1691), and A/H1N1pdm09 virus was the most commonly identified subtype with 38.07% (198/520), followed by A/H1N2 (16.3%) and A/H3N2 (5.2%). Year-round influenza activity was noted in pigs, with the highest incidence between June and September. Phylogenetic analyses revealed that the IAVs were closely related to human IAV strains belonging to A/H1N1pdm09 and seasonal H3N2 lineages. Genetic analysis revealed that Senegalese strains possessed several key amino acid changes, including D204 and N241D in the receptor binding site, S31N in the M2 gene and P560S in the PA protein. Serological analyses revealed that 83.5% (95%CI = 81.6-85.3) of the 1636 sera tested were positive for the presence of antibodies against either H9N2, H5N1, H7N7 or H5N2. Influenza H7N7 (54.3%) and H9N2 (53.6%) were the dominant avian subtypes detected in Senegalese pigs. Given the co-circulation of multiple subtypes of influenza viruses among Senegalese pigs, the potential exists for the emergence of new hybrid viruses of unpredictable zoonotic and pandemic potential in the future.

Potential Effects of Habitat Change on Migratory Bird Movements and Avian Influenza Transmission in the East Asian-Australasian Flyway

Wild waterbirds, and especially wild waterfowl, are considered to be a reservoir for avian influenza viruses, with transmission likely occurring at the agricultural-wildlife interface. In the past few decades, avian influenza has repeatedly emerged in China along the East Asian-Australasian Flyway (EAAF), where extensive habitat conversion has occurred. Rapid environmental changes in the EAAF, especially distributional changes in rice paddy agriculture, have the potential to affect both the movements of wild migratory birds and the likelihood of spillover at the agricultural-wildlife interface. To begin to understand the potential implications such changes may have on waterfowl and disease transmission risk, we created dynamic Brownian Bridge Movement Models (dBBMM) based on waterfowl telemetry data. We used these dBBMM models to create hypothetical scenarios that would predict likely changes in waterfowl distribution relative to recent changes in rice distribution quantified through remote sensing. Our models examined a range of responses in which increased availability of rice paddies would drive increased use by waterfowl and decreased availability would result in decreased use, predicted from empirical data. Results from our scenarios suggested that in southeast China, relatively small decreases in rice agriculture could lead to dramatic loss of stopover habitat, and in northeast China, increases in rice paddies should provide new areas that can be used by waterfowl. Finally, we explored the implications of how such scenarios of changing waterfowl distribution may affect the potential for avian influenza transmission. Our results provide advance understanding of changing disease transmission threats by incorporating real-world data that predicts differences in habitat utilization by migratory birds over time.

Prevalence, Seroprevalence and Risk Factors of Avian Influenza in Wild Bird Populations in Korea: A Systematic Review and Meta-Analysis.

Since the first recorded outbreak of the highly pathogenic avian influenza (HPAI) virus (H5N1) in South Korea in 2003, numerous sporadic outbreaks have occurred in South Korean duck and chicken farms, all of which have been attributed to avian influenza transmission from migratory wild birds. A thorough investigation of the prevalence and seroprevalence of avian influenza viruses (AIVs) in wild birds is critical for assessing the exposure risk and for directing strong and effective regulatory measures to counteract the spread of AIVs among wild birds, poultry, and humans. In this study, we performed a systematic review and meta-analysis, following the PRISMA guidelines, to generate a quantitative estimate of the prevalence and seroprevalence of AIVs in wild birds in South Korea. An extensive search of eligible studies was performed through electronic databases and 853 records were identified, of which, 49 fulfilled the inclusion criteria. The pooled prevalence and seroprevalence were estimated to be 1.57% (95% CI: 0.98, 2.51) and 15.91% (95% CI: 5.89, 36.38), respectively. The highest prevalence and seroprevalence rates were detected in the Anseriformes species, highlighting the critical role of this bird species in the dissemination of AIVs in South Korea. Furthermore, the results of the subgroup analysis also revealed that the AIV seroprevalence in wild birds varies depending on the detection rate, sample size, and sampling season. The findings of this study demonstrate the necessity of strengthening the surveillance for AIV in wild birds and implementing strong measures to curb the spread of AIV from wild birds to the poultry population.

Effects of the 2022 extreme droughts on avian influenza transmission risk in Poyang Lake

Effects of the 2022 extreme droughts on avian influenza transmission risk in Poyang Lake

Reducing zoonotic avian influenza transmission at household poultry slaughter using a behaviour change tool for limited literacy audiences.

Human infections in Egypt with highly pathogenic avian influenza (HPAI) likely due to airborne transmission of HPAI virus (HPAIV) during home slaughter of poultry predominately affect women and children, who are the primary caregivers of household poultry. This study developed a safe contained poultry slaughter procedure to reduce airborne HPAIV and zoonotic infections and simultaneously created an educational outreach tool for teaching the modified procedure. The tool designed for limited literacy audiences used two illustrated posters and handouts for teaching the safe contained poultry slaughter procedure. The posters were developed with advice of animal health professionals and then refined by target audience women's focus groups. These women's focus groups proved to be the critical step for assuring the understanding, acceptance, effectiveness and accuracy of the outreach tool. The safe contained poultry slaughter procedure was designed to be low or no cost, sustainable by using a universal implement found in village households and designed as a minor variation of standard poultry halal slaughter. It was crafted to be culturally appropriate and religiously acceptable.

Seasonality of influenza and coseasonality with avian influenza in Bangladesh, 2010–19: a retrospective, time-series analysis

Seasonal and avian influenza viruses circulate among human and poultry populations in Bangladesh. However, the epidemiology of influenza is not well defined in this setting. We aimed to characterise influenza seasonality, examine regional heterogeneity in transmission, and evaluate coseasonality between circulating influenza viruses in Bangladesh. In this retrospective, time-series study, we used data collected between January, 2010, and December, 2019, from 32 hospital-based influenza surveillance sites across Bangladesh. We estimated influenza peak timing and intensity in ten regions using negative binomial harmonic regression models, and applied meta-analytic methods to determine whether seasonality differed across regions. Using live bird market surveillance data in Dhaka, Bangladesh, we estimated avian influenza seasonality and examined coseasonality between human and avian influenza viruses. Over the 10-year study period, we included 8790 human influenza cases and identified a distinct influenza season, with an annual peak in June to July each year (peak calendar week 27·6, 95% CI 26·7-28·6). Epidemic timing varied by region (I2=93·9%; p<0·0001), with metropolitan regions peaking earlier and epidemic spread following a spatial diffusion pattern based on geographical proximity. Comparatively, avian influenza displayed weak seasonality, with moderate year-round transmission and a small peak in April (peak calendar week 14·9, 95% CI 13·2-17·0), which was out of phase with influenza peaks in humans. In Bangladesh, influenza prevention and control activities could be timed with annual seasonality, and regional heterogeneity should be considered in health resource planning. Year-round avian influenza transmission poses a risk for viral spillover, and targeted efforts will be crucial for mitigating potential reassortment and future pandemic threats. Canadian Institute of Health Research Vanier Canada Graduate Scholarship.

Evidence for Water-Borne Transmission of Highly Pathogenic Avian Influenza H5N1 Viruses.

In this study, we isolated 10 H5N1 strains from water samples in Dongting Lake and 4 H5N1 strains from lakeside backyard poultry. These isolates belonged to three distinct clades (clade 2.3.2, 2.3.4, and 7). Phylogenetic analysis showed a diversified genome constellation. The genetic characteristics of some viruses isolated from water samples were extremely similar to those from lakeside poultry. Pathogenic experiments showed that selected represented isolates in this study were highly pathogenic for SPF chickens but had a diversified virulence in mice. The results of our study suggested the potential transmission of avian influenza (H5N1) between the poultry and wild waterfowls and water body around the habitat may play an important role.

Direct and indirect transmission of avian influenza: results from a calibrated agent-based model

Direct and indirect transmission of avian influenza: results from a calibrated agent-based model

Avian–human influenza epidemic model with diffusion, nonlocal delay and spatial homogeneous environment

In this paper, an avian–human influenza epidemic model with diffusion, nonlocal delay and spatial homogeneous environment is investigated. This model describes the transmission of avian influenza among poultry, humans and environment. The behavior of positive solutions to a reaction–diffusion system with homogeneous Neumann boundary conditions is investigated. By means of linearization method and spectral analysis the local asymptotical stability is established. The global asymptotical stability for the poultry sub-system is studied by spectral analysis and by using a Lyapunov functional. For the full system, the global stability of the disease-free equilibrium is studied using the comparison Theorem for parabolic equations. Our result shows that the disease-free equilibrium is globally asymptotically stable, whenever the contact rate for the susceptible poultry is small. This suggests that the best policy to prevent the occurrence of an epidemic is not only to exterminate the asymptomatic poultry but also to reduce the contact rate between susceptible humans and the poultry environment. Numerical simulations are presented to illustrate the main results.

Host diversity and behavior determine patterns of interspecies transmission and geographic diffusion of avian influenza A subtypes among North American wild reservoir species.

Wild birds can carry avian influenza viruses (AIV), including those with pandemic or panzootic potential, long distances. Even though AIV has a broad host range, few studies account for host diversity when estimating AIV spread. We analyzed AIV genomic sequences from North American wild birds, including 303 newly sequenced isolates, to estimate interspecies and geographic viral transition patterns among multiple co-circulating subtypes. Our results show high transition rates within Anseriformes and Charadriiformes, but limited transitions between these orders. Patterns of transition between species were positively associated with breeding habitat range overlap, and negatively associated with host genetic distance. Distance between regions (negative correlation) and summer temperature at origin (positive correlation) were strong predictors of transition between locations. Taken together, this study demonstrates that host diversity and ecology can determine evolutionary processes that underlie AIV natural history and spread. Understanding these processes can provide important insights for effective control of AIV.

Frequency and patterns of exposure to live poultry and the potential risk of avian influenza transmission to humans in urban Bangladesh

Avian influenza is endemic in Bangladesh, where greater than 90% of poultry are marketed through live poultry markets (LPMs). We conducted a population-based cross-sectional mobile telephone survey in urban Dhaka, Bangladesh to investigate the frequency and patterns of human exposure to live poultry in LPMs and at home. Among 1047 urban residents surveyed, 74.2% (95% CI 70.9–77.2) reported exposure to live poultry in the past year, with the majority of exposure occurring on a weekly basis. While visiting LPMs was less common amongst females (40.3%, 95% CI 35.0–45.8) than males (58.9%, 95% CI 54.0–63.5), females reported greater poultry exposure through food preparation, including defeathering (13.2%, 95% CI 9.5–17.9) and eviscerating (14.8%, 95% CI 11.2–19.4) (p < 0.001). A large proportion of the urban population is frequently exposed to live poultry in a setting where avian influenza viruses are endemic in LPMs. There is thus not only ample opportunity for spillover of avian influenza infections into humans in Dhaka, Bangladesh, but also greater potential for viral reassortment which could generate novel strains with pandemic potential.

Avian influenza transmission risk along live poultry trading networks in Bangladesh

Live animal markets are known hotspots of zoonotic disease emergence. To mitigate those risks, we need to understand how networks shaped by trading practices influence disease spread. Yet, those practices are rarely recorded in high-risk settings. Through a large cross-sectional study, we assessed the potential impact of live poultry trading networks’ structures on avian influenza transmission dynamics in Bangladesh. Networks promoted mixing between chickens sourced from different farming systems and geographical locations, fostering co-circulation of viral strains of diverse origins in markets. Viral transmission models suggested that the observed rise in viral prevalence from farms to markets was unlikely explained by intra-market transmission alone, but substantially influenced by transmission occurring in upstream network nodes. Disease control interventions should therefore alter the entire network structures. However, as networks differed between chicken types and city supplied, standardised interventions are unlikely to be effective, and should be tailored to local structural characteristics.

Vaccination with inactivated virus against low pathogenic avian influenza subtype H9N2 does not prevent virus transmission in chickens

H9N2 subtype avian influenza has spread dramatically in China ever since first reported in the 1990s. A national vaccination program for poultry was initiated in 1998. Field isolation data show that the widely used inactivated H9N2 vaccine does not provide effective control of the transmission of this low pathogenic avian influenza (LPAI) virus in poultry. Current research has focused on two reasons: (i) insufficient immune response triggered by the vaccination with the inactivated virus, (ii) the occurrence of escape mutants selected by vaccine-induced immune pressure. However, the lack of effectivity of the inactivated virus vaccine to sufficiently reduce transmission has been noticed. We mimicked the natural infection and transmission process of the H9N2 virus in vaccinated and non-vaccinated chickens. A statistical model was used to estimate the transmission rate parameters among vaccinated chickens, varying in serum hemagglutinin inhibition titers (HIT) and non-vaccinated chickens. We demonstrate, for the first time, that the transmission is not sufficiently reduced by the H9N2 vaccine, even when vaccinated chickens have an IgG serum titer (HIT>23), which is considered protective for vaccination against homologous highly pathogenic avian influenza (HPAI) virus. Our study does, on the other hand, cast new light on virus transmission and immune escape of LPAI H9N2 virus in vaccinated chickens populations, and shows that new mitigation strategies against LPAI viruses in poultry are needed.

Live poultry feeding and trading network and the transmission of avian influenza A(H5N6) virus in a large city in China, 2014–2015

ObjectivesTo understand the transmission mechanisms of the avian influenza A(H5N6) virus. MethodsThis study explored the live poultry feeding and trading network (LPFTN) around Changsha city, China. Field epidemiological investigations were performed in Changsha to investigate the LPFTN with the environmental samples systematically collected during 2014–2015 to monitor and analyze the spread of the A(H5N6) virus. Two surveillance systems were also applied to find possible human cases of A(H5N6) infection. ResultThe information of all the 665 live poultry farming sites, five wholesale markets, and 223 retail markets in Changsha was collected to investigate the LPFTN. Moreover, about 840 environmental samples were systematically collected from the LPFTN during 2014–2015 to monitor the spread of the A(H5N6) virus, with 8.45% (71/840) positive for the N6 subtype. Furthermore, the full genome sequences of 10 A(H5N6) viruses detected from the environmental samples were obtained, which were then characterized and phylogenetically analyzed with the corresponding gene segments of the A(H5N6) virus obtained from GenBank, to determine the source of human infection. ConclusionIt was demonstrated that the LPFTN provided a platform for the H5N6 transmission, and formed an infectious pool for the spread of the virus to humans.

Rich dynamics of a Filippov avian-only influenza model with a nonsmooth separation line

Depopulation of birds has been authenticated to be an effective measure in controlling avian influenza transmission. In this work, we establish a Filippov avian-only model incorporating a threshold policy control. We choose the index—the maximum between the infected threshold level I_{T} and the product of the number of susceptible birds S and a ratio threshold value ξ—to decide on whether to trigger the control measures or not, which then leads to a discontinuous separation line and two pieces of sliding-mode domains. Meanwhile, one more sliding-mode domain gives birth to more complex dynamics. We investigate the global dynamical behavior of the Filippov model, including the real and/or virtual equilibria and the two sliding modes and their dynamics. The solutions will eventually stabilize at the real endemic equilibrium of the subsystem or the pseudoequilibria on the two sliding modes due to different threshold values. Therefore an effective and efficient threshold policy is essential to control the influenza by driving the number of infected birds below a certain level or at a previously given level.

Avian Influenza-Killed Vaccine on Tissue Distribution and Shedding of Avian Influenza Virus H9N2 in Ducklings.

Ducks play an important role in the transmission of avian influenza to poultry farms. Because of the importance of vaccination in reducing virus shedding, this study evaluated avian influenza-killed vaccine H9N2 on tissue distribution and shedding of avian influenza virus H9N2 in ducklings. One hundred-day-old ducklings were purchased and, after bleeding from 20 birds, were kept in four separate rooms under standard conditions. Groups 1 and 2 were vaccinated at 9 days, and groups 2 and 3 were challenged with 0.1 ml of allantoic fluid containing 105 EID50 (A/chicken/Iran/Aid/2013(H9)) virus intranasally at 30 days. Group 4 chicks were kept as the control group. Chicks were observed two times daily. On days 1, 3, 5, and 8 after inoculation, 3 chicks were randomly selected from each group and cloaca and trachea swabs samples were collected from each bird. Then the ducklings were euthanized and trachea, lung, spleen, intestine, liver, and brain tissue samples were collected for molecular detection. The virus was detected in the tissues and tracheal and cloacal swabs by polymerase chain reaction (PCR), and anti-AIV titres were measured by HI test. The results showed no clinical signs in the challenged groups. In the vaccinated challenged group, virus was detected only in cloacal swabs, but in the unvaccinated challenged group, virus was detected more in tracheal swabs than in cloacal swabs. In challenged-unvaccinated chicks, virus was detected in the trachea and lungs, and in challenged-vaccinated birds, virus was detected in the intestines. In conclusion, vaccinating ducks against the AI H9N2 virus reduced shedding and tissue distribution of AI viruses in challenged ducks.