Highly Pathogenic Avian Influenza H5N1 Outbreaks Research Articles

Wild bird origin Influenza A subtype diversity and reassortment events during the HPAI H5N1 outbreak in Chile, 2022-2023. Proceeding of The First International Avian Influenza Summit, University of Arkansas- October 16-17, 2023"

Highly pathogenic avian influenza (HPAI) H5N1 viruses continue to pose a significant threat to animal and human health worldwide. Since the onset of the HPAI H5N1 outbreak in South America, our research group has been conducting environmental influenza A virus (IAV) surveillance in different wetlands throughout Chile to detect and characterize circulating IAV strains. Between November 2022 and June 2023, we collected and screened 3275 environmental samples for IAV by RT-qPCR targeting the M gene. Of these, 133 were IAV-positive (4.1\%). Further testing by H5-specific RT-qPCR revealed that 14 (10.5\%) of the positive samples corresponded to HPAI H5 2.3.4.4b, collected during the month of November (2), December (8 positives), January (1 positive), March (1 Positive) and June (1 positive). Samples obtained during spring (November and December) were obtained at the Lluta River estuary in the extreme north of Chile. Samples obtained during Summer (January and March) were obtained in Lluta and at Punta Arenas, located in the extreme South of Chile. The sample obtained in Winter (June) was obtained in Maipo, located in Central Chile. Sequence analysis of 6 fully sequenced H5N1 viruses revealed that all segments were closely related to other H5N1 2.3.4.4b viruses circulating at the time in South America. Interestingly, we also obtained several other subtypes of low pathogenic avian influenza viruses (LPAI) during the sampling period: H13N9, H13N8, H12N5, H8N4, H6N8, H6N5, H5N7, H4N6, H2N8 and H2N2. Phylogenetic analysis of these viruses revealed that locally circulating LPAI H12N5, H6N8, and H5N7 subtype viruses, additionally to 4 more viruses without subtype information, had reassorted with HPAI viruses in at least one of the PA and NP segments. The role that these novel reassortant viruses play in the ecology of IAV in Chile and their pathogenic potential is unknown; however, in light of these reassortment events, further surveillance is warranted to detect potentially novel HPAI H5Nx viruses circulating in wild birds in Chile that could have unknown pathogenic and transmission potential.

Integration of Epidemiological and Genomic Data to Investigate H5N1 HPAI Outbreaks in Northern Italy in 2021-2022.

Between October 2021 and April 2022, 317 outbreaks caused by highly pathogenic avian influenza (HPAI) H5N1 viruses were notified in poultry farms in the northeastern Italian regions. The complete genomes of 214 strains were used to estimate the genetic network based on the similarity of the viruses. An exponential random graph model (ERGM) was used to assess the effect of 'at-risk contacts', 'same owners', 'in-bound/out-bound risk windows overlap', 'genetic differences', 'geographic distances', 'same species', and 'poultry company' on the probability of observing a link within the genetic network, which can be interpreted as the potential propagation of the epidemic via lateral spread or a common source of infection. The variables 'same poultry company' (Est. = 0.548, C.I. = [0.179; 0.918]) and 'risk windows overlap' (Est. = 0.339, C.I. = [0.309; 0.368]) were associated with a higher probability of link formation, while the 'genetic differences' (Est. = -0.563, C.I. = [-0.640; -0.486]) and 'geographic distances' (Est. = -0.058, C.I. = [-0.078; -0.038]) indicated a reduced probability. The integration of epidemiological data with genomic analyses allows us to monitor the epidemic evolution and helps to explain the dynamics of lateral spreads casting light on the potential diffusion routes. The 2021-2022 epidemic stresses the need to further strengthen the biosecurity measures, and to encourage the reorganization of the poultry production sector to minimize the impact of future epidemics.

Molecular characterisation of hemagglutinin and neuraminidase genes of the first highly pathogenic Avian Influenza H5N1 2.3.2.1c virus isolated from Sabah, Malaysia.

Highly Pathogenic Avian Influenza (HPAI) is a highly contagious disease in poultry. The outbreaks can lead to flock mortality up to 100% in two to three days. In July 2018, high mortality in a commercial layer farm in Kauluan village, Sabah was reported. Samples were sent to Veterinary Research Institute Ipoh for diagnosis. Virus isolation and molecular detection is carried out simultaneously. The causative agent was then identified as AI H5N1 virus by real time reverse transcription-polymerase chain reaction (RT-PCR). The virus was then subjected for further nucleotide sequencing of full length hemagglutinin (HA) and neuraminidase (NA) gene. The PQRERRRKR/GLF motif at the HA cleavage site indicated that the isolate was of HPAI virus. Phylogenetic analysis of the HA gene showed that the isolate was belonged to the clade 2.3.2.1c virus. In the HA gene, besides the S133A substitution, the virus possesses conserved amino acid at most of the avian receptor binding sites including the glutamine (Q) and glycine (G) at position 222 and 224 respectively, indicating that the virus retains the avian-type receptor binding preference. As such, the zoonotic potential of the virus was relatively low. On the other hand, though the N154D and T156A substitution were detected in the same gene, the pandemic potential of this Sabah 2.3.2.1c virus is low in the absence of the Q222L, G224S, H103Y, N220K and T315I. A typical 20 amino acid deletion with loss of four corresponding glycosylation sites in the NA stalk region was visible. Though three NA resistance markers were detected, the virus was predicted to be sensitive to NA inhibitor. This is the first HPAI H5N1 outbreak in Sabah. The introduction of this virus into East Malaysia for the first time raised an alert alarm of the future epidemic potential. Strict farm biosecurity, continuous surveillance programme in poultry, wild birds, migratory birds; molecular epidemiology as well as risk assessment for the virus with pandemic potential are needed in dealing with emergence of new influenza virus in the country.

Spatiotemporal analysis of highly pathogenic avian influenza (H5N1) outbreaks in poultry in Egypt (2006 to 2017)

BackgroundIn Egypt, the highly pathogenic avian influenza (HPAI) subtype H5N1 is endemic and possesses a severe impact on the poultry. To provide a better understanding of the distributional characteristics of HPAI H5N1 outbreaks in Egypt, this study aimed to explore the spatiotemporal pattern and identify clusters of HPAI H5N1 outbreaks in Egypt from 2006 to 2017.ResultsThe Epidemic curve (EC) was constructed through time series analysis; in which six epidemic waves (EWs) were revealed. Outbreaks mainly started in winter peaked in March and ended in summer. However, newly emerged thermostable clades (2.2.1.1 and 2.2.1.2) during the 4th EW enabled the virus to survive and cause infection in warmer months with a clear alteration in the seasonality of the epidemic cycle in the 5th EW. The endemic situation became more complicated by the emergence of new serotypes. As a result, the EC ended up without any specific pattern since the 6th EW to now. The spatial analysis showed that the highest outbreak density was recorded in the Nile Delta considering it as the ‘Hot spot’ region. By the 6th EW, the outbreak extended to include the Nile valley. From spatiotemporal cluster epidemics, clustering in the Delta was a common feature in all EWs with primary clusters consistently detected in the hot-spot region, but the location and size varied with each EW. The highest Relative Risk (RR) regions in an EW were noticed to contain the primary clusters of the next EW and were found to include stopover sites for migratory wild birds. They were in Fayoum, Dakahlia, Qalyobiya, Sharkia, Kafr_Elsheikh, Giza, Behera, Menia, and BeniSuef governorates. Transmission of HPAI H5N1 occurred from one location to another directly resulted in a series of outbreaks forming neighboring secondary clusters. The absence of geographical borders between the governorates in addition to non-restricted movements of poultry and low vaccination and surveillance coverage contributed to the wider spread of infection all over Egypt and to look like one epidemiological unit.ConclusionOur findings can help in better understanding of the characteristics of HPAI H5N1 outbreaks and the distribution of outbreak risk, which can be used for effective disease control strategies.Graphical abstract

Surveillance on respiratory diseases reveals enzootic circulation of both H5 and H9 avian influenza viruses in small-scale commercial layer farms of Bangladesh.

Poultry production in Bangladesh has been experiencing H5N1 highly pathogenic avian influenza (HPAI) and H9N2 low pathogenic avian influenza (LPAI) for the last 14years. Vaccination of chickens against H5 HPAI is in practice since the end of 2012. Subsequently, the official reporting of HPAI outbreaks gradually decreased. However, the true extent of circulation of avian influenza virus (AIV) in commercial poultry production is not clear. To explore this, we conducted active surveillance in 422 small-scale commercial layer farms in 20 villages of Mymensingh and Tangail districts of Bangladesh during 2017 and 2018 for the presence of diseases with respiratory signs. A total of 88 farms with respiratory disease problems were identified and investigated during the surveillance. In addition, 22 small-scale commercial layer farms in the neighbouring areas with respiratory disease problem were also investigated on request from the farmers. Pooled samples of oropharyngeal swabs from live birds or respiratory tissues from dead birds of the farm suffering from respiratory disease problem were tested for molecular detection of avian influenza virus (AIV), Newcastle disease virus (NDV), infectious bronchitis virus (IBV), infectious laryngotracheitis virus (ILTV), Mycoplasma gallisepticum and Avibacterium paragallinarum. A total of 110 farms (88 in the surveillance site and 22 in the neighbouring region) were investigated, and one or more respiratory pathogens were detected from 89 farms. AIV was detected in 57 farms often concurrently with other pathogens. Among these 57 farms, H5, H9, both H5 and H9 or non-H5 and non-H9 AIV were detected in 28, 9, 13 or 7 farms, respectively. Birds of most of the H5 AIV-positive farms did not present typical clinical signs or high mortality. Twenty such farms were observed longitudinally, which had only 1.05%-5.50% mortality but a marked drop in egg production. This widespread circulation of H5 AIV along with H9 AIV and other pathogens in small-scale commercial layer farms, often with low mortality, reaffirms the enzootic circulation of AIV in Bangladesh, which may escape syndromic surveillance focused on unusual mortality only. To reduce public health risks, strengthening of the control programme with comprehensive vaccination, enhanced biosecurity, improved surveillance and outbreak response is suggested.

Satellite telemetry tracks flyways of Asian Openbill storks in relation to H5N1 avian influenza spread and ecological change

BackgroundAsian Openbills, Anastomus oscitans, have long been known to migrate from South to Southeast Asia for breeding and nesting. In Thailand, the first outbreak of H5N1 highly pathogenic avian influenza (HPAI) infection in the Openbills coincided with the outbreak in the poultry. Therefore, the flyways of Asian Openbills was determined to study their role in the spread of H5N1 HPAI virus to poultry and wild birds, and also within their flocks.ResultsFlyways of 5 Openbills from 3 colonies were monitored using Argos satellite transmitters with positioning by Google Earth Programme between 2007 and 2013. None of the Openbills tagged with satellite telemeters moved outside of Thailand. Their home ranges or movement areas varied from 1.6 to 23,608 km2 per month (95% utility distribution). There was no positive result of the viral infection from oral and cloacal swabs of the Openbills and wild birds living in the vicinity by viral isolation and genome detection during 2007 to 2010 whereas the specific antibody was not detected on both Openbills and wild birds by using microneutralization assay after 2008. The movement of these Openbills did not correlate with H5N1 HPAI outbreaks in domestic poultry but correlated with rice crop rotation and populations of the apple snails which are their preferred food. Viral spread within the flocks of Openbills was not detected.ConclusionsThis study showed that Openbills played no role in the spread of H5N1 HPAI virus, which was probably due to the very low prevalence of the virus during the monitoring period. This study revealed the ecological factors that control the life cycle of Asian Openbills.

Effects of Highly Pathogenic Avian Influenza H5N1 Outbreak in Nepal from Financial and Social Perspectives: A Case Study

The outbreaks of highly pathogenic avian influenza (HPAI) H5N1 have serious public health, economic and social implications. After the first two report of HPAI H5N1 outbreak in Nepal in Jhapa in 2009, a third outbreak was reported in Pokhara the following year where more than 11,000 birds were culled to control the disease. However, the financial and social effects of the Pokhara bird flu outbreak were never assessed. The objectives of this study were to evaluate the local financial and social effects of HPAI H5N1 outbreak in Pokhara and to understand farmers and consumers perceptions on bird flu and the control measures implemented by the government. A total of 200 people including poultry farmers, butchers, veterinary drug dealers, feed suppliers, and consumers were interviewed using the semi-structured questionnaire. The result showed that the direct loss of Pokhara bird flu outbreak from the culling of birds was more than 4.5 million Nepali rupees. The small scale commercial and backyard farmers and the butchers were the most affected from this outbreak. A large proportion of the consumers temporarily stopped to consume chicken meat and shifted to other meat sources. Most of the participants in this study had at least heard about the bird flu. The farmers were unhappy by the compensation provided by the government and perceived that the government control efforts were not satisfactory and were provided little assistance for their rehabilitation. In conclusion, there was a momentary local financial and social effect of the Pokhara bird flu outbreak which may not very important from the macroeconomic point of view but is important for the affected small-scale farmers and the butchers. It is recommended that the government review their policy and provide small scale commercial and backyard farmer a compensation that is closer to the market price and promote largescale poultry farmers to go for insurance.

H7N9 and H5N1 avian influenza suitability models for China: accounting for new poultry and live-poultry markets distribution data

In the last two decades, two important avian influenza viruses infecting humans emerged in China, the highly pathogenic avian influenza (HPAI) H5N1 virus in the late nineties, and the low pathogenic avian influenza (LPAI) H7N9 virus in 2013. China is home to the largest population of chickens (4.83 billion) and ducks (0.694 billion), representing, respectively 23.1 and 58.6% of the 2013 world stock, with a significant part of poultry sold through live-poultry markets potentially contributing to the spread of avian influenza viruses. Previous models have looked at factors associated with HPAI H5N1 in poultry and LPAI H7N9 in markets. However, these have not been studied and compared with a consistent set of predictor variables. Significant progress was recently made in the collection of poultry census and live-poultry market data, which are key potential factors in the distribution of both diseases. Here we compiled and reprocessed a new set of poultry census data and used these to analyse HPAI H5N1 and LPAI H7N9 distributions with boosted regression trees models. We found a limited impact of the improved poultry layers compared to models based on previous poultry census data, and a positive and previously unreported association between HPAI H5N1 outbreaks and the density of live-poultry markets. In addition, the models fitted for the HPAI H5N1 and LPAI H7N9 viruses predict a high risk of disease presence for the area around Shanghai and Hong Kong. The main difference in prediction between the two viruses concerned the suitability of HPAI H5N1 in north-China around the Yellow sea (outlined with Tianjin, Beijing, and Shenyang city) where LPAI H7N9 has not spread intensely.

Vaccination against H5 avian influenza virus induces long-term humoral immune responses in flamingoes (Phoenicopterus spp.)

Avian influenza (AI) can represent a threat to endangered wild birds, as demonstrated with the H5N1 highly pathogenic AI (HPAI) outbreaks. Vaccination against AI using inactivated H5-vaccines has been shown to induce humoral immune response in zoo bird species. In this study, the long-term efficacy of H5-vaccination was evaluated in flamingoes from Barcelona Zoo. Specific H5-antibody titres were maintained at high levels (geometric mean titres ≥32) for over 7 years after vaccination, both against the H5N9 and H5N3 vaccine strains, as well as H5N3 and H5N1 reference strains. In addition the breadth of the immune response was also studied by testing antibody production against H1-, H3-, H4-, H7-, and H10-subtypes. It was observed that most flamingoes presented specific antibodies against H1 virus subtypes, but titres to the other HA-subtypes were rarely detected. We show that AI-vaccines can induce immunity lasting seven years in flamingoes, which suggests that vaccination can provide long term protection from HPAI outbreaks in zoo birds.

Assessment of practices, capacities and incentives of poultry chain actors in implementation of highly pathogenic avian influenza mitigation measures in Ghana.

The animal health services‐seeking behaviour of animal owners related to prevention and control of animal diseases may influence their decisions as to whether or not to use services provided by the public or private sectors. The specific objective of this paper was to assess the practices, capacities and incentives of actors involved in highly pathogenic avian influenza (HPAI) control to provide information for prevention and control in Ghana. Questionnaires were designed based on specific practices, incentives and capacities associated with each mitigation measure that was being assessed. Two peacetime preventive mitigation measures (biosecurity and reporting) and two outbreak containment measures (culling with compensation and movement control) were selected for evaluation. Supply chain actors were characterised based on baseline information. Tables were generated showing proportions of respondents in the various response categories in Likert‐scale type itemised questionnaire. Mean scores (and their standard deviations) for the various actors with regard to mitigation measures were calculated. Pair‐wise comparisons were done using t‐ratio statistic and significance of differences were determined at a Bonferroni adjusted P‐value of 0.0024. The study found statistically significant differences between certain actors for practices (biosecurity, reporting, culling and compensation and movement controls), incentives (reporting and movement control) and capacities (reporting and movement control). The findings provide lessons to help improve education and messages on HPAI and to help provide technical assistance targeted at specific actors to prevent and control future HPAI H5N1 outbreaks in Ghana.

Systematic review and meta-analyses of cases and deaths associated with highly pathogenic avian influenza H5N1 in humans and poultry.

Abstract From 2003 to date (2015), confirmed highly pathogenic avian influenza (HPAI) H5N1 outbreaks in poultry and humans have been reported, however, certain quantitative parameters remain lacking. We obtained 846 reports of HPAI H5N1 outbreaks in poultry in Africa (2006-2015), and 844 reports in humans globally (2003-2015) from different databases. Data were filtered and analysed using meta-analyses. The outputs were generated for each country included in the study and for overall morbidities, mortalities and case fatalities (for poultry and humans). Approximately 11.6 million poultry were included in the analyses as susceptible with 1.9 million cases and 1.7 million deaths in poultry. In humans, 449 deaths were linked to influenza A H5N1 infections. For all poultry outbreaks in 2006-2015 in Africa, an overall mean apparent morbidity of 48.7% ( n =1 850 589) was estimated, with overall mean apparent mortality being 40.2% ( n =1 705 388) and overall mean case fatality rate (CFR) for HPAI H5N1 outbreaks in poultry being 86.4% ( n =1 705 388). In humans, the overall mean CFR for A H5N1 globally for 2003-2015 was 62.3% ( n =449). Indonesia, Egypt and Vietnam had higher proportions of all human deaths associated with the A H5N1 and Egypt had a significant age-sex bias. Improved reporting and effective quantitation remain key to understanding the characteristics of the virus.

Prevalence of avian influenza virus in wild birds before and after the HPAI H5N8 outbreak in 2014 in South Korea.

Since 2003, highly pathogenic avian influenza (HPAI) virus outbreaks have occurred five times in Korea, with four HPAI H5N1 outbreaks and one HPAI H5N8 outbreak. Migratory birds have been suggested to be the first source of HPAI in Korea. Here, we surveyed migratory wild birds for the presence of AI and compared regional AI prevalence in wild birds from September 2012 to April 2014 for birds having migratory pathways in South Korea. Finally, we investigated the prevalence of AI in migratory birds before and after HPAI H5N8 outbreaks. Overall, we captured 1617 migratory wild birds, while 18,817 feces samples and 74 dead birds were collected from major wild bird habitats. A total of 21 HPAI viruses were isolated from dead birds, and 86 low pathogenic AI (LPAI) viruses were isolated from captured birds and from feces samples. Spatiotemporal distribution analysis revealed that AI viruses were spread southward until December, but tended to shift north after January, consistent with the movement of migratory birds in South Korea. Furthermore, we found that LPAI virus prevalences within wild birds were notably higher in 2013-2014 than the previous prevalence during the northward migration season. The data from our study demonstrate the importance of the surveillance of AI in wild birds. Future studies including in-depth genetic analysis in combination with evaluation of the movement and ecology of migratory birds might help us to bridge the gaps in our knowledge and better explain, predict, and ultimately prevent future HPAI outbreaks.

Highly Pathogenic Avian Influenza H5N1 in Mainland China.

Highly pathogenic avian influenza (HPAI) H5N1 has posed a significant threat to both humans and birds, and it has spanned large geographic areas and various ecological systems throughout Asia, Europe and Africa, but especially in mainland China. Great efforts in control and prevention of the disease, including universal vaccination campaigns in poultry and active serological and virological surveillance, have been undertaken in mainland China since the beginning of 2006. In this study, we aim to characterize the spatial and temporal patterns of HPAI H5N1, and identify influencing factors favoring the occurrence of HPAI H5N1 outbreaks in poultry in mainland China. Our study shows that HPAI H5N1 outbreaks took place sporadically after vaccination campaigns in poultry, and mostly occurred in the cold season. The positive tests in routine virological surveillance of HPAI H5N1 virus in chicken, duck, goose as well as environmental samples were mapped to display the potential risk distribution of the virus. Southern China had a higher positive rate than northern China, and positive samples were mostly detected from chickens in the north, while the majority were from duck in the south, and a negative correlation with monthly vaccination rates in domestic poultry was found (R = −0.19, p value = 0.005). Multivariate panel logistic regression identified vaccination rate, interaction between distance to the nearest city and national highway, interaction between distance to the nearest lake and wetland, and density of human population, as well as the autoregressive term in space and time as independent risk factors in the occurrence of HPAI H5N1 outbreaks, based on which a predicted risk map of the disease was derived. Our findings could provide new understanding of the distribution and transmission of HPAI H5N1 in mainland China and could be used to inform targeted surveillance and control efforts in both human and poultry populations to reduce the risk of future infections.

Development of broadly reactive H5N1 vaccine against different Egyptian H5N1 viruses

The H5N1 highly pathogenic avian influenza (HPAI) virus was isolated for the first time in Egypt in 2006, since then, the virus has become endemic causing a significant threat to the poultry industry and humans. H5N1 HPAI outbreaks continue to occur despite extensive vaccination programs that have been implemented nationwide in different poultry species. Several studies showed that the co-circulating H5N1 viruses in Egypt are genetically and antigenically distant raising a question on the cross protective efficacy of commercial vaccines. In this study, we introduced mutations at the antigenic sites of the hemagglutinin (HA) to broaden reactivity of the Egyptian H5N1 virus. A reverse genetically created variant H5N1 virus (A/chicken/Egypt/1063/2010) with five amino acid mutations (G140R, Y144F, I190L, K192Q, D43N) in the HA gene showed enhanced cross reactivity. This virus showed up to 16 fold increase in reactivity to the classic-lineageH5N1viruses measured by hemagglutination inhibition (HI) assay while maintaining similar level of reactivity with the variant-lineage viruses compared to wild-type virus. In addition, a single amino acid substitution (N165H), which removes potential glycosylation site at the HA globular head of two classic strains (A/chicken/Egypt/527/2012 and A/chicken/Egypt/102d/2010) broadened the reactivity to antisera generated against H5N1 viruses from different clusters. The broadened reactivity of the mutant viruses were also confirmed by testing reactivity of antisera prepared from the mutant viruses against reference viruses from both classic and variant clades. The virus neutralization test using selected antisera and viruses further confirmed the cross HI results. This study highlights that targeted mutation in the HA may be effectively used as a tool to develop broadly reactive influenza vaccines to cope with the continuous antigenic evolution of viruses.

Collective resistance to HPAI H5N1 surveillance in the Thai cockfighting community: Insights from a social anthropology study

Farmers may organize themselves to collectively manage risks such as animal diseases. Our study shows some evidence of such organization among fighting cock owners in Thailand. Fighting cocks were specifically targeted by HPAI (Highly Pathogenic Avian Influenza) H5N1 surveillance and control measures in Thailand because they were thought to pose a high risk of spreading diseases. In this work, we used a social-anthropological approach to gain an inside view of the issues associated with HPAI H5N1 surveillance in the cockfighting community in Thailand. Based on a qualitative analysis of data collected through in-depth interviews and observation of cockfighters’ practices, we found that fighting cock owners share a sense of belonging to the same community based on a common culture, values, interests, practices, and internal rules, including rules to manage poultry diseases. During the HPAI H5N1 outbreaks, these rules may have contributed to mitigating the potential risk associated with the intense movements of fighting cocks inside the country. Nevertheless, this community, despite the high awareness and know-how of its members regarding poultry diseases, has shown a strong reluctance to comply with HPAI surveillance programs. We suggest that this reluctance is due to important gaps between the logic and rationales underlying surveillance and those associated with cockfighting activities. Our study highlights the need for multi and trans-disciplinary research involving the social sciences to analyze interactions between stakeholders and the collective actions implemented by communities to face risks.

Community preparedness for highly pathogenic Avian influenza on Bali and Lombok, Indonesia

The Asia-Pacific region is the likeliest location for the next significant outbreak of highly pathogenic avian influenza (HPAI). Indonesia has experienced HPAI H5N1 outbreaks in poultry and humans each year since 2003 and has had the highest case fatality rate for human cases. The purposes of this study were to capture the knowledge of avian influenza and of poultry-raising practices in two regions of Indonesia and to evaluate the impact and extent of activities undertaken to 2010 through the National Strategic Plan for Avian Influenza Control at the village level. A combination of quantitative and qualitative methods was used to investigate the multiple influences on behaviours, decisions and actions taken by poultry-raising households, and by villages and communities, regarding the threat of HPAI. Between June 2010 and May 2011 a structured survey of 400 households was conducted on Lombok and of 402 on Bali, inviting Sector 3 (small-scale independent commercial poultry farms) and Sector 4 (village household) poultry raisers to participate. Focus groups and in-depth interviews were convened with key stakeholders, including livestock and animal health and public health officials, community leaders and villagers. From the focus group and in-depth interviews, it appears that the flow of information through the national HPAI control program has been efficient at the top levels (from national to provincial, then to districts and subdistricts). However, these findings show that effective transmission of information from subdistrict to rural village level and from village leaders to community members has been limited. The degree of community preparedness for HPAI on Bali and Lombok appears minimal. Knowledge of government activities was more extensive at Bali sites, while only limited government programs and activities occurred at the village level on Lombok. Activities conducted by government agencies from provincial to village level were limited in scope and need to be further developed to ensure safe poultry-handling practices and biosecurity measures. On both Bali and Lombok, community respondents knew the signs and symptoms of sick birds but did not differentiate well between HPAI and other bird diseases. On both islands, more than 60% of respondents were reluctant to report sudden deaths of poultry. The lack of a government compensation program for destroyed flocks contributed to this unwillingness to report. While the Indonesian government's planning efforts for HPAI are commendable, the plan has not been effective, as it depends on the cooperative actions of people with small rural farms who have not been consulted in the development of the plan, have not been adequately instructed on the nature of the plan, and perceive no benefits to themselves from prevention efforts. Context-appropriate mechanisms for communicating zoonotic risk and options for risk mitigation that do not result in net loss to poor households are also needed.

Spatio-temporal epidemiology of highly pathogenic avian influenza (subtype H5N1) in poultry in eastern India

In India, majority outbreaks of highly pathogenic avian influenza (HPAI) H5N1 have occurred in eastern states of West Bengal, Assam and Tripura. This study aimed to identify disease clusters and risk factors of HPAI H5N1 in these states, for targeted surveillance and disease control. A spatial scan statistic identified two significant disease clusters in West Bengal and Assam, occurring during January and November–December 2008, respectively. Key risk factors were identified at sub-district level using bootstrapped logistic regression and boosted regression trees model. With both methods, HPAI H5N1 outbreaks in backyard poultry were associated with accessibility in terms of time taken to access a city with >50,000 persons, human population density and duck density (P<0.005). In addition, areas at lower elevation were also identified as high risk by BRT model. It is recommended that risk-based surveillance should be implemented in high duck density areas and all live-bird markets in high-throughput locations.

Evaluating the impact of environmental temperature on global highly pathogenic avian influenza (HPAI) H5N1 outbreaks in domestic poultry.

The emergence and spread of highly pathogenic avian influenza (HPAI) A virus subtype H5N1 in Asia, Europe and Africa has had an enormously socioeconomic impact and presents an important threat to human health because of its efficient animal-to-human transmission. Many factors contribute to the occurrence and transmission of HPAI H5N1 virus, but the role of environmental temperature remains poorly understood. Based on an approach of integrating a Bayesian Cox proportional hazards model and a Besag-York-Mollié (BYM) model, we examined the specific impact of environmental temperature on HPAI H5N1 outbreaks in domestic poultry around the globe during the period from 1 December 2003 to 31 December 2009. The results showed that higher environmental temperature was a significant risk factor for earlier occurrence of HPAI H5N1 outbreaks in domestic poultry, especially for a temperature of 25 °C. Its impact varied with epidemic waves (EWs), and the magnitude of the impact tended to increase over EWs.

Zero-inflated models for identifying disease risk factors when case detection is imperfect: Application to highly pathogenic avian influenza H5N1 in Thailand

Logistic regression models integrating disease presence/absence data are widely used to identify risk factors for a given disease. However, when data arise from imperfect surveillance systems, the interpretation of results is confusing since explanatory variables can be related either to the occurrence of the disease or to the efficiency of the surveillance system. As an alternative, we present spatial and non-spatial zero-inflated Poisson (ZIP) regressions for modelling the number of highly pathogenic avian influenza (HPAI) H5N1 outbreaks that were reported at subdistrict level in Thailand during the second epidemic wave (July 3rd 2004 to May 5th 2005). The spatial ZIP model fitted the data more effectively than its non-spatial version. This model clarified the role of the different variables: for example, results suggested that human population density was not associated with the disease occurrence but was rather associated with the number of reported outbreaks given disease occurrence. In addition, these models allowed estimating that 902 (95% CI 881–922) subdistricts suffered at least one HPAI H5N1 outbreak in Thailand although only 779 were reported to veterinary authorities, leading to a general surveillance sensitivity of 86.4% (95% CI 84.5–88.4). Finally, the outputs of the spatial ZIP model revealed the spatial distribution of the probability that a subdistrict could have been a false negative. The methodology presented here can easily be adapted to other animal health contexts.

야생조류에 대한 조류인플루엔자 예찰의 중요성과 연구 동향

Abstract : Avian influenza viruses (AIV) have been isolated from a wide range of domestic and wild birds. Wildbirds, predominantly ducks, geese and gulls form the reservoir of AIV in nature. The viruses in wild bird populationsare a potential source of widespread infections in poultry. Active surveillance for AIV infection provides informationregarding AIV distribution, and global AIV surveillance can play a key role in the early recognition of highly pathogenicavian influenza (HPAI). Since 2003 in Korea, there have been four H5N1 HPAI outbreaks caused by clade 2.5, 2.2and 2.3.2. Therefore, improvement of AIV surveillance strategy is required to detect HPAI viruses effectively. Thisarticle deals with the major events establishing the role of wild birds in the natural history of influenza in Korea.We highlighted the need for continuous surveillance in wild birds and characterization of these viruses to understandAIV epidemiology and host ecology in Korea.Keywords : avian influenza, epidemiology, poultry, surveillance, wild bird