Serological and virological surveillance of avian influenza virus in domestic ducks of the north-east region of Bangladesh

Highly pathogenic avian influenza H5N8 and H5N1 outbreaks in Algerian avian livestock production

Avian Alpha-influenza-virus (AIV) massively affects poultry, targeting mainly the respiratory tract for virus replication. Recently, two major H5N8 and H5N1 outbreaks caused tremendous losses in Algerian poultry. The clinical symptoms that had not been seen in the past didn't prompt a rapid reaction to control the epidemics. We report here the characteristics of these outbreaks and the epidemiological status of AIV in Algeria. Following autopsy observation samples from target organs were taken and analyzed by the classical real-time reverse transcription polymerase chain reaction (RRT-PCR). Specific PCR HA and NA identification was used for subtyping H5 and N1/N8 genes. Systemic damage was observed in the upper-respiratory tracts with hemorrhagic and congestive tracheas, lungs, proventriculus, gut, and cecal tonsils were bloody. Out of 77 positive cases 13 were H5N8, 8 H5N1, and 10 H5Nx strains. These findings raise questions about the strain's pathotype considering severe organ damage and high mortality.

A highly pathogenic avian influenza virus H5N1 clade 2.3.4.4 detected in Samara Oblast, Russian Federation

Avian influenza (AI) is a global problem impacting birds and mammals, causing economic losses in commercial poultry farms and backyard settings. In 2022, over 8,500 AI cases were reported worldwide, with the H5 subtype being responsible for many outbreaks in wild and domestic birds. In the territory of the Russian Federation, outbreaks of AI have been massively reported since 2020, both among domestic bird species and wild bird species. Wild migratory birds often serve as natural reservoirs for AI viruses, and interactions between bird species can lead to the emergence of new, highly pathogenic variants through genetic recombination between strains. In order to combat the widespread outbreaks of the disease and potential risks of further spread in 2021, monitoring studies were conducted in the Samara Oblast, the southeastern region of European Russian Federation. These studies aimed to diagnose and characterize circulating AI virus variants among wild migratory birds during waterfowl hunting in areas of mass nesting. Among the 98 shot birds, a highly pathogenic A/H5N1 AI virus was detected in a Eurasian Teal from the Bolshechernigovsky district. It was classified into clade 2.3.4.4 based on the cleavage site structure of HA. Phylogenetic analysis showed a high relatedness of the identified strain in the Samara Oblast with field isolates from Russia, Nigeria, Bangladesh, and Benin. The article emphasizes the importance of monitoring AI virus spread in both wild and poultry, highlighting the need for timely information exchange to assess risks. Further comprehensive studies are necessary to understand virus dissemination pathways.

Semi-Scavenging Poultry as Carriers of Avian Influenza Genes

Ducks are the natural reservoir of influenza A virus and the central host for the avian influenza virus (AIV) subtype H5N1, which is highly pathogenic. Semi-scavenging domestic ducks allow for the reemergence of new influenza subtypes which could be transmitted to humans. We collected 844 cloacal swabs from semi-scavenging ducks inhabiting seven migratory bird sanctuaries of Bangladesh for the molecular detection of avian influenza genes. We detected the matrix gene (M gene) using real-time RT-PCR (RT-qPCR). Subtyping of the AIV-positive samples was performed by RT-qPCR specific for H5, H7, and H9 genes. Out of 844 samples, 21 (2.488%) were positive for AIV. Subtyping of AIV positive samples (n = 21) revealed that nine samples (42.85%) were positive for the H9 subtype, five (23.80%) were positive for H5, and seven (33.33%) were negative for the three genes (H5, H7, and H9). We detected the same genes after propagating the virus in embryonated chicken eggs from positive samples. Semi-scavenging ducks could act as carriers of pathogenic AIV, including the less pathogenic H9 subtype. This can enhance the pathogenicity of the virus in ducks by reassortment. The large dataset presented in our study from seven areas should trigger further studies on AIV prevalence and ecology.

Prevalence and risk factors of Avian Influenza Viruses among household ducks in Chattogram, Bangladesh

Avian influenza viruses (AIV) increase commercial and backyard poultry mortality and morbidity, reduces egg production, and elevates public health risk. Household ducks propagate and transmit HPAI and LPAI viruses between domesticated and wild birds in Southeast Asian countries, including Bangladesh. This study was conducted to identify epidemiological factors associated with AIV infection among household ducks at Chattogram, Bangladesh. We randomly selected and collected blood and oropharyngeal swab samples from 281 households ducks. We evaluated the serum for AIV antibody using cELISA and tested for H5 and H9 subtypes using the HI test. We tested the swabs with real-time reverse transcriptase PCR (rRT-PCR) for M gene, and H5, H9 subtypes. In the duck populations, the household level AIV sero-prevalence was 57.7% (95% CI: 51.6-63.3) and RNA prevalence was 2.4% (95% CI: 1.0-5.0). H5 and H9 subtype sero-prevalence was 31.5% (95% CI: 22.2-42.0) and 23.9% (95% CI: 15.6-33.9). H5 and H9 subtype RNA prevalence were 0% (95% CI: 0.0-1.3) and 2.4% (95% CI: 1.0-5.0). We determined household-level OR (Odds Ratios) for the "combined (mixed materials-mud and concrete or metallic)" category was 2.2 (95% CI: 1.1-4.2) compared with "wooden/bamboo" category (p = 0.02); 2.8 (95% CI: 1.2-6.6) in households with duck plague vaccine coverage compared with no coverage (p = 0.01); and 2.4 (95% CI: 0.6-9.7) in households that threw dead birds in bushes and the roadside compared with households that buried or threw dead birds in garbage pits (p = 0.21). M gene phylogenetic analysis compared M gene sequences to previously reported Bangladeshi H9N2 isolates. The evidence presented here shows AIV circulation in the Chattogram, Bangladesh study areas. AIV reduction can be achieved through farmer education of proper farm management practices.

Longitudinal Analysis of Influenza A(H5) Sero-Surveillance in Myanmar Ducks, 2006-2019

Between 2006 and 2019, serological surveys in unvaccinated domestic ducks reared outdoors in Myanmar were performed, using a haemagglutination inhibition (HI) test, to confirm H5 avian influenza virus circulation and assess temporal and spatial distribution. Positive test results occurred every year that samples were collected. The annual proportion of positive farms ranged from 7.1% to 77.2%. The results revealed silent/sub-clinical influenza A (H5) virus circulation, even in years and States/Regions with no highly pathogenic avian influenza (HPAI) outbreaks reported. Further analysis of the 2018/19 results revealed considerable differences in seroconversion rates between four targeted States/Regions and between years, and showed seroconversion before and during the sampling period. By the end of the trial, a high proportion of farms were seronegative, leaving birds vulnerable to infection when sold. Positive results likely indicate infection with Gs/GD/96-lineage H5Nx HPAI viruses rather than other H5 subtype low-pathogenicity avian influenza viruses. The findings suggested persistent, but intermittent, circulation of Gs/GD/96-lineage H5Nx HPAI viruses in domestic ducks, despite the veterinary services' outbreak detection and control efforts. The role of wild birds in transmission remains unclear but there is potential for spill-over in both directions. The findings of this study assist the national authorities in the design of appropriate, holistic avian influenza control programs.

Identification and molecular characterization of H9N2 viruses carrying multiple mammalian adaptation markers in resident birds in central-western wetlands in India

We report here a targeted risk-based study to investigate the presence of influenza A viruses at the migratory-wild-domestic bird interface across the major wetlands of central India's Maharashtra state during the winter migration season. The H9N2 viruses have been isolated and confirmed in 3.86% (33/854) of the fecal samples of resident birds. To investigate the genetic pools of H9N2 circulating in resident birds, we sequenced two isolates of H9N2 from distant wetlands. Sequence and phylogenetic analyses have shown that these viruses are triple reassortants, with HA, NA, NP, and M genes belonging to G1 sub-lineage (A/quail/Hong Kong/G1/1997), PB2, PB1, and NS genes originating from the prototype Eurasian lineage (A/mallard/France/090360/2009) and PA gene deriving from Y439/Korean-like (A/duck/Hong Kong/Y439/97) sub-lineage. It was confirmed not only that four of their gene segments had a high genetic association with the zoonotic H9N2 virus, A/Human/India/TCM2581/2019, but also that they had many molecular markers associated with mammalian adaptation and enhanced virulence in mammals including the unique multiple basic amino acids, KSKR↓GLF at the HA cleavage site, and analog N-and O-glycosylation patterns on HA with that of the zoonotic H9N2 virus. Furthermore, future experiments would be to characterize these isolates biologically to address the public health concern. Importantly, due to the identification of these viruses at a strategic geographical location in India (a major stop-over point in the Central Asian flyway), these novel viruses also pose a possible threat to be exported to other regions via migratory/resident birds. Consequently, systematic investigation and active monitoring are a prerequisite for identifying and preventing the spread of viruses of zoonotic potential by enforcing strict biosecurity measures.

Effect of COVID-19 pandemic on anxiety depression and intention to go to hospital in chronic patients

OBJECTIVE

The aim of this study was to investigate the effects of the COVID-19 pandemic on anxiety depression and intention to go to the hospital in chronic patients.

METHODS

The Bostan Intention to Go to Hospital Scale developed by one researcher (SB) as the data collection tool and the Beck Anxiety-Depression Inventories were used.

RESULTS

Of all patients, 56.8% stated that they would go to the hospital in case of emergency and 28.3% expressed that they did not want to go to the hospital even in this case. 50% of the participants said that they did not want to go to the hospital under any circumstances during the pandemic process. As a result of the correlation analysis, there was an inverse correlation between the anxiety-depression levels and encountering COVID-19 patients and having a relative with COVID-19 (P = .001). Inverse correlation was found between intention to go to hospital and encountering COVID-19 patients (P = .001).

CONCLUSION

It was revealed that chronic patients did not have any intentions to go to hospital during the COVID-19 pandemic and only half of the people were willing to go to the hospital in case of emergency. Anxiety and depression levels were found to increase when COVID-19 patients were encountered or a relative had COVID-19.

Potential risk factors of avian influenza virus infection in asymptomatic commercial chicken flocks in selected areas of Bangladesh during 2019

Objective:

Avian influenza is a zoonotic disease with a pandemic potential that can infect avian and mammalian species, including humans. Studies aimed at investigating avian influenza virus (AIV) status in asymptomatic chickens and their shedding are uncommon in Bangladesh. Therefore, the current study aimed to examine the distribution of AIV subtypes in asymptomatic commercial chicken flocks and to identify the possible risk factors associated with this infection in two selected sub-districts of Bangladesh.

Materials and Methods:

A total of 582 oropharyngeal swabs were collected from 23 chicken farms during 2019 and evaluated for the presence of AIV and its subtypes by real-time reverse transcription PCR assays. Risk factors associated with AIV infection were analyzed from questionnaire data.

Results:

Overall, AIV prevalence was 7.73% (n = 45) with 7.39% and 7.92% in Dhamrai and Gazipur Sadar sub-districts, respectively. In AIV-positive samples, the prevalence of A/H5N1, A/H5N2, A/H9N1, and A/H9N2 was 31.11%, 28.89%, 6.67%, and 8.89%, respectively. None of the samples were positive for N6 and N8. The odds ratio (OR) of AIV infection was 1.15 in broiler versus layer and 2 in Sonali versus layer chickens. The OR was 1.95 for medium versus small, 2.6 for large versus small flock size, 1.5 for moderate versus good biosecurity, and 2.92 for poor versus good biosecurity practicing farms.

Conclusion:

The results demonstrated that A/H5N1, A/H5N2, A/H9N1, and A/H9N2 are circulating in asymptomatic chickens of selected areas. Strict farm biosecurity practices and avoiding higher flock density are recommended to prevent AIV spread in the study.

Surveillance of multiple subtype specific antibodies against avian influenza viruses among egg yolk in wild ducks from northeast China, 2017-2019

Over the past decade, various avian influenza viruses have been isolated from wild ducks found in the northeast of China. To monitor the prevalence of multiple subtype specific AIVs antibodies, 1705 wild ducks' eggs from six wetlands of northeast China were analyzed for surveillance of H1, H3, H5, and H7 AIVs antibodies by c-ELISA and HI test from Jan 2017 to Dec 2019. The results show that the combined frequency of multiple subtype specific AIVs antibodies were H1 (12.32%), H3 (8.15%), H5 (2.05%), and H7 (3.46%) respectively. Therefore, a detailed analysis of the geographical distribution of AIVs in China, and the risk factors for human infection is of vital importance. This study provides basic data for other researchers to deeply study AIVs distribution characteristics, and for governments to develop detailed measures to control the spread of AIVs.

Prevalence and Distribution of Avian Influenza Viruses in Domestic Ducks at the Waterfowl-Chicken Interface in Wetlands

Ducks are a natural reservoir of influenza A viruses (IAVs) and can act as a reassortment vessel. Wetlands, such as Hakaluki and Tanguar haor in Bangladesh, have unique ecosystems including domestic duck (Anas platyrhynchos domesticus) rearing, especially household and free-range ducks. A cross-sectional study was, therefore, conducted to explore avian influenza status and its distribution and risk factors in the wetland areas. During the three consecutive winters of 2015-2017, specifically in December of these years, we collected a total of 947 samples including blood, oropharyngeal and cloacal swabs from domestic ducks (free-range duck (n = 312 samples) and household ducks (n = 635 samples) in wetlands. We screened serum samples using a nucleoprotein competitive enzyme-linked immunosorbent assay (c-ELISA) to estimate seroprevalence of IAV antibodies and swab samples by real-time reverse transcriptase polymerase chain reaction (rRT-PCR) to detect IA viral M gene. Eleven (11) M gene positive samples were subjected to sequencing and phylogenetic analysis. Serological and viral prevalence rates of IAVs were 63.8% (95% CI: 60.6-66.8) and 10.7% (8.8-12.8), respectively. Serological and viral RNA prevalence rates were 51.8% (95% CI: 47.2-56.4) and 10.2% (7.6-13.3) in Hakaluki haor, 75.6% (71.5-79.4) and 11.1% (8.5-14.3) in Tanguar haor, 66.3% (62.5-69.9) and 11.2% (8.8-13.9) in household ducks and 58.7% (52.9-64.2) and 9.6% (6.5-13.4) in free-range ducks, respectively. The risk factors identified for higher odds of AI seropositive ducks were location (OR = 2.9, 95% CI: 2.2-3.8, p < 0.001; Tanguar haor vs. Hakaluki haor), duck-rearing system (OR = 1.4, 1.1-1.8, household vs. free-range), farmer's education status (OR = 1.5, 1.2-2.0, p < 0.05 illiterate vs. literate) and contact type (OR = 3.0, 2.1-4.3, p < 0.001; contact with chicken vs. no contact with chicken). The risk factors identified for higher odds of AI RNA positive ducks were farmer's education status (OR = 1.5, 1.0-2.3, p < 0.05 for illiterate vs literate), contact type (OR = 2.7, 1.7-4.2, p < 0.001; ducks having contact with chicken vs. ducks having contact with waterfowl). The phylogenetic analysis of 11 partial M gene sequences suggested that the M gene sequences detected in free-range duck were very similar to each other and were closely related to the M gene sequences of previously reported highly pathogenic avian influenza (HPAI) and low pathogenic avian influenza (LPAI) subtypes in waterfowl in Bangladesh and Southeast Asian countries. Results of the current study will help provide significant information for future surveillance programs and model IAV infection to predict the spread of the viruses among migratory waterfowl, free-range ducks and domestic poultry in Bangladesh.

An assessment on potential risk pathways for the incursion of highly pathogenic avian influenza virus in backyard poultry farm in Bangladesh

Background and Aim:

Highly pathogenic avian influenza (HPAI) is a deadly virus of zoonotic potential. The study mainly aims to determine the risk pathways (RPs) for the probable incursion of HPAI virus (HPAIV) in backyard poultry in Bangladesh.

Materials and Methods:

The study involves expert elicitation technique. The concept map determines the possible RPs. The map consists of 16 concepts, each with nodes from which probabilities of an event originates. These probabilities are described by qualitative descriptors ranging from negligible to high. Risk assessment has been performed using the subjective risk assessment tool.

Results:

The tool demonstrates positive correlation among groups of experts in the level of agreement by scoring RP; however, the level of agreement varies from 71% to 93% among group of experts. The median risk score of viral incursion through the “Exposure of backyard poultry with farm poultry in the trading market” was 11 and ranked as top, followed by “Contaminated live bird market environment” and “Sharing common scavenging space with migratory birds” (median risk score, 10.5; rank, 2), and “Scavenging of infected slaughtered poultry remnants by backyard poultry” (median risk score, 5.3; rank, 3) when no control options were applied along with the RPs. After applying or considering control option along with contaminated live bird market environment, the median risk score was reduced to 5.0. Applying a specific control option along with each RP reduced estimated median risk scores for HPAIV incursions.

Conclusion:

This study provides an insight into the incursion risks of HPAIV through various RPs in backyard poultry in Bangladesh.

Controlling Avian Influenza Virus in Bangladesh: Challenges and Recommendations

Avian influenza virus (AIV) remains a huge challenge for poultry production with negative repercussions for micro- and macro-economy and public health in Bangladesh. High (HP) H5N1 and low pathogenicity (LP) H9N2 AIV are currently endemic in poultry, and both have been reported to infect humans sporadically. Multiple virus introductions of different clades of HPAIV H5N1, reassorted genotypes, and on-going diversification of LPAIV H9N2 create a highly volatile virological environment which potentially implicates increased virulence, adaptation to new host species, and subsequent zoonotic transmission. Allotropy of poultry rearing systems and supply chains further increase the risk of virus spreading, which leads to human exposure and fosters the emergence of new potentially pre-pandemic virus strains. Here, we review the epidemiology, focusing on (i) risk factors for virus spreading, (ii) viral genetic evolution, and (iii) options for AIV control in Bangladesh. It is concluded that improved control strategies would profit from the integration of various intervention tools, including effective vaccination, enhanced biosecurity practice, and improved awareness of producers and traders, although widespread household poultry rearing significantly interferes with any such strategies. Nevertheless, continuous surveillance associated with rapid diagnosis and thorough virus characterization is the basis of such strategies.

Prevalence and Diversity of Avian Influenza Virus Hemagglutinin Sero-Subtypes in Poultry and Wild Birds in Bangladesh

Highly pathogenic avian influenza H5 viruses have pandemic potential, cause significant economic losses and are of veterinary and public health concerns. This study aimed to investigate the distribution and diversity of hemagglutinin (HA) subtypes of avian influenza virus (AIV) in poultry and wild birds in Bangladesh. We conducted an avian influenza sero-surveillance in wild and domestic birds in wetlands of Chattogram and Sylhet in the winter seasons 2012-2014. We tested serum samples using a competitive enzyme-linked immunosorbent assay (c-ELISA), and randomly selected positive serum samples (170 of 942) were tested using hemagglutination inhibition (HI) to detect antibodies against the 16 different HA sero-subtypes. All AIV sero-subtypes except H7, H11, H14 and H15 were identified in the present study, with H5 and H9 dominating over other subtypes, regardless of the bird species. The diversity of HA sero-subtypes within groups ranged from 3 (in household chickens) to 10 (in migratory birds). The prevalence of the H5 sero-subtype was 76.3% (29/38) in nomadic ducks, 71.4% (5/7) in household chicken, 66.7% (24/36) in resident wild birds, 65.9% (27/41) in migratory birds and 61.7% (29/47) in household ducks. Moreover, the H9 sero-subtype was common in migratory birds (56%; 23/41), followed by 38.3% (18/47) in household ducks, 36.8% (14/38) in nomadic ducks, 30.6% (11/66) in resident wild birds and 28.5% (2/7) in household chickens. H1, H4 and H6 sero-subtypes were the most common sero-subtypes (80%; 8/10, 70%; 7/10 and 70%; 7/10, respectively) in migratory birds in 2012, H9 in resident wild birds (83.3%; 5/6) and H2 in nomadic ducks (73.9%; 17/23) in 2013, and the H5 sero-subtype in all types of birds (50% to 100%) in 2014. The present study demonstrates that a high diversity of HA subtypes circulated in diverse bird species in Bangladesh, and this broad range of AIV hosts may increase the probability of AIVs' reassortment and may enhance the emergence of novel AIV strains. A continued surveillance for AIV at targeted domestic-wild bird interfaces is recommended to understand the ecology and evolution of AIVs.

Active virological surveillance in backyard ducks in Bangladesh: detection of avian influenza and gammacoronaviruses

Domestic waterfowl play an important role in the perpetuation and transmission of avian pathogens including avian influenza viruses (AIV) of low and high pathogenicity, which pose severe economic and public health concerns in Bangladesh. This study focused on active surveillance of several avian viral pathogens with a special reference to AIV in selected backyard duck populations in Bangladesh. A total of 500 pooled oropharyngeal and cloacal samples from individual ducks of four districts were tested by real time PCRs for the presence of AIV, avian avulavirus-1, anatid herpesvirus-1, avian parvovirus, avian bornavirus and avian coronavirus. The investigation identified 27 (5.4%) ducks positive for AIV and 12 (2.4%) positive for avian coronavirus. In 13 samples, RNA specific for AIV H4N6 was detected. Phylogenetic analysis of the AIV haemagglutinin H4 and neuraminidase N6 genes suggested a clustering of Bangladeshi AIV H4N6 in Eurasian lineage group 2. Other AIV positive samples had very low virus loads (Cq > 36) and were not subtyped. Coronaviral sequences of a fragment of the polymerase gene were related to Eurasian-Australian duck gamma-coronaviruses. Our current active surveillance in free-range domestic backyard ducks in Bangladesh failed to detect highly pathogenic (HP) AIV in contrast to our previous passive monitoring study. Nevertheless, active monitoring of domestic duck populations may be important to highlight presence and transmission dynamics of economically less important AIV that still may serve as reassortment partners for the generation of new HP and zoonotic AIV. RESEARCH HIGHLIGHTS Active surveillance for viral pathogens in domestic free-range backyard ducks. Detection of avian influenza virus subtype H4N6. First identification of avian gammacoronavirus in ducks in Bangladesh.

Impact of global climate change on livestock health: Bangladesh perspective

The global carbon emission rate, due to energy-driven consumption of fossil fuels and anthropogenic activities, is higher at any point in mankind history, disrupting the global carbon cycle and contributing to a major cause of warming of the planet with air and ocean temperatures, which is rising dangerously over the past century. Climate change presents challenges both direct and indirect for livestock production and health. With more frequent extreme weather events including increased temperatures, livestock health is greatly affected by resulting heat stress, metabolic disorder, oxidative stress, and immune suppression, resulting in an increased propensity for disease incidence and death. The indirect health effects relate to the multiplication and distribution of parasites, reproduction, virulence, and transmission of infectious pathogens and/or their vectors. Managing the growing crossbreeding livestock industry in Bangladesh is also at the coalface for the emerging impacts of climate change, with unknown consequences for the incidence of emerging and re-emerging diseases. Bangladesh is now one of the most vulnerable nations to global climate change. The livestock sector is considered as a major part of food security for Bangladesh, alongside agriculture, and with one of the world’s largest growing economies, the impacts are exaggerated with this disaster. There has been no direct study conducted on the impact of climate change on livestock health and the diseases in Bangladesh. This review looks to explore the linkage between climate change and livestock health and provide some guidelines to combat the impact on livestock from the Bangladesh perspective.

Co-subsistence of avian influenza virus subtypes of low and high pathogenicity in Bangladesh: Challenges for diagnosis, risk assessment and control

Endemic co-circulation of potentially zoonotic avian influenza viruses (AIV) of subtypes H5N1 and H9N2 (G1 lineage) in poultry in Bangladesh accelerated diversifying evolution. Two clinical samples from poultry obtained in 2016 yielded five different subtypes (highly pathogenic [HP] H5N1, HP H5N2, HP H7N1, HP H7N2, H9N2) and eight genotypes of AIV by plaque purification. H5 sequences grouped with clade 2.3.2.1a viruses while N1 was related to an older, preceding clade, 2.2.2. The internal genome segments of the plaque-purified viruses originated from clade 2.2.2 of H5N1 or from G1/H9N2 viruses. H9 and N2 segments clustered with contemporary H9N2 strains. In addition, HP H7 sequences were detected for the first time in samples and linked to Pakistani HP H7N3 viruses of 2003. The unexpected findings of mixtures of reassorted HP H5N1 and G1-like H9N2 viruses, which carry genome segments of older clades in association with the detection of HP H7 HA segments calls for confirmation of these results by targeted surveillance in the area of origin of the investigated samples. Hidden niches and obscured transmission pathways may exist that retain or re-introduce genome segments of older viruses or reassortants thereof which causes additional challenges for diagnosis, risk assessment and disease control.

Survivability of highly pathogenic avian influenza virus (H5N1) in naturally preened duck feathers at different temperatures

Ducks are the "Trojan Horses" for Asian H5N1 avian influenza viruses (AIV) and attain carrier status without displaying overt infection. These birds help in the spread of the virus among the poultry and human population through direct or indirect contact. Preen oil is the secretion of preen gland of water birds such as ducks. In a process called preening, the water birds spread preen oil across their feather and body. Preen oil has been known to play a significant role in the accumulation of various pathogens including Highly Pathogenic Avian Influenza (HPAI) from water onto feathers. However, the studies are scarce on the role of preen oil in the survivability of HPAIV. We conducted a simulative study to analyse the effect of preen oil on the survivability of the HPAI virus (H5N1) on duck feathers. Duck feather samples along with relevant controls were spiked with the H5N1 virus at two different initial concentrations (10⁴ EID₅₀ and 10⁶ EID₅₀ ), stored at 37°C, 25°C and 10°C temperatures and tested at regular intervals for percent infectivity by egg culture method and qRT-PCR. The infectivity and viral load were significantly higher in naturally preened duck feathers in comparison to the three preen oil deficit controls at both low and high initial concentrations of virus (10⁴ EID₅₀ and 10⁶ EID₅₀ ). Maximum persistence was seen at 10°C in naturally preened duck feathers spiked with 10⁶ EID₅₀ concentration of viruses. It was also seen that depletion of preen oil from duck feathers reduced the persistence of the virus. These results demonstrate that preen oil plays a significant role in survivability and protection of HPAIV on duck feathers. This study herein will present new avenues in understanding one of the epidemiological niches of HPAIV.

Review analysis and impact of co-circulating H5N1 and H9N2 avian influenza viruses in Bangladesh

Almost the full range of 16 haemagglutinin (HA) and nine neuraminidase subtypes of avian influenza viruses (AIVs) has been detected either in waterfowl, land-based poultry or in the environment in Bangladesh. AIV infections in Bangladesh affected a wide range of host species of terrestrial poultry. The highly pathogenic avian influenza (AI) H5N1 and low pathogenic AI H9N2 were found to co-circulate and be well entrenched in the poultry population, which has caused serious damage to the poultry industry since 2007. By reviewing the available scientific literature, the overall situation of AIVs in Bangladesh is discussed. All Bangladeshi (BD) H5N1 and H9N2 AIV sequences available at GenBank were downloaded along with other representative sequences to analyse the genetic diversity among the circulating AIVs in Bangladesh and to compare with the global situation. Three different H5N1 clades, 2.2.2, 2.3.2.1 and 2.3.4.2, have been detected in Bangladesh. Only 2.3.2.1a is still present. The BD LP H9N2 viruses mostly belonged to the H9 G1 lineage but segregated into many branches, and some of these shared internal genes with HP viruses of subtypes H7N3 and H5N1. However, these reassortment events might have taken place before introduction to Bangladesh. Currently, H9N2 viruses continue to evolve their HA cleavage, receptor binding and glycosylation sites. Multiple mutations in the HA gene associated with adaptation to mammalian hosts were also observed. Strict biosecurity at farms and gradual phasing out of live-bird markets could be the key measures to better control AIVs, whereas stamping out is not a practicable option in Bangladesh. Vaccination also could be an additional tool, which however, requires careful planning. Continuous monitoring of AIVs through systematic surveillance and genetic characterisation of the viruses remains a hallmark of AI control.