Comparative infectivity and transmissibility studies of wild-bird and chicken-origin highly pathogenic avian influenza viruses H5N8 in chickens

Respiratory disease complex due to mixed viral infections in chicken in Jordan

The global distribution of avian respiratory viruses highlights the need for effective surveillance programs and international collaboration to monitor viral circulation and implement timely control measures. In the current study, we aim to provide a comprehensive overview of avian respiratory viral infections in the poultry flocks in Jordan, focusing on the major viruses involved, their epidemiology, clinical manifestations, and evolution based on viroinformatics that will be helpful to improve the diagnostic methods, and control strategies including vaccines in the region. In this research, various poultry broiler groups in Jordan experiencing respiratory symptoms were tested for respiratory viral pathogens from January 2021 to February 2022. The mortality rates observed in the examined groups varied between 6% and 40%. The identified strains were authenticated using the RT-qPCR assay. Furthermore, they underwent in-depth characterisation through the sequencing of the complete spike (S1) gene for infectious bronchitis virus (IBV) and the haemagglutinin (HA) gene for avian influenza virus (AIV) subtype H9N2. Co-infection of IBV and AIV H9N2 viruses was detected through molecular analysis. The IBV strains showed affiliation with the variant groups GI-16 (3 strains) and GI-23 (9 strains) and exhibited numerous mutations. Meanwhile, H9N2 avian influenza viruses displayed various changes in amino acids within the HA gene, suggesting the influence of antibody-driven selection pressure. The phylogenetic analysis revealed that the H9N2 viruses identified in this investigation shared close genetic ties with EG3 (3 strains) and the Middle East group (ME1; 8 strains). These strains have been recently found in Jordan and nearby countries in the Middle East. Moreover, their HA genes exhibited similarities to viruses belonging to the G1-like lineage. In conclusion, avian respiratory viral infections remain a significant concern for the poultry industry, requiring constant vigilance and proactive measures to minimise their impact. Continued surveillance, robust diagnostic methods, effective vaccines, and international cooperation are essential components of a comprehensive approach to combat avian respiratory viral infections (AI, IBV, ND and ILT 'viruses) and safeguard avian health and global poultry production.

Evaluation of the immuno-stimulatory effect of aqueous neem (Azadirachta indica) leaf extract against highly pathogenic avian influenza (H5N8) in experimental chickens

The recently detected clade 2.3.4.4 of the highly pathogenic avian influenza (HPAI) H5N8 virus in poultry encouraged us to study the efficacy of the 6 most extensively used saleable H5 poultry vaccinations (bivalent [AI + ND], Re-5 H5N1, H5N1, H5N3, monovalent AI, monovalent ND) with or without aqueous 8% neem (Azadirachta indica) leaf extract as an immunostimulant. One hundred thirty birds were randomly divided into 7 groups. Groups 1, 2, 3, 4, 5, and 6 were divided into 2 subgroups (G1a, G2a, G3a, G4a, G5a, G6a) and (G1b, G2b, G3b, G4b, G5b, G6b) with 10 birds each. Subgroups (G1a, G2a, G3a, G4a, G5a, G6a) received the (bivalent [AI + ND], Re-H5N1, H5N1, H5N3, monovalent AI, monovalent ND) vaccines, while subgroups (G1b, G2b, G3b, G4b, G5b, G6b) received the same previous vaccination but treated with neem leaf extract administrated 2 d before and after vaccination, and G7 with 10 birds was kept unvaccinated as positive control group. Clinical signs of the challenged group showed conjunctivitis, closed eyes, cyanosis in comb and wattle, ocular discharge, and greenish diarrhea, while postmortem lesions showed congested trachea and lung, hemorrhage on the shank, proventriculus, and pancreas; gelatinous fluid submandibular, congestion of all organs (septicemia), mottled spleen. The clinical signs and lesions were mild in neem leaf extract treated with bivalent vaccine and Re-H5N1 while moderate in monovalent vaccine and H5N3 with or without neem leaf extract treated and reached severe in the group immunized with H5N1 with or without neem leaf extract treatment. The protection levels in the bivalent vaccine (AI + ND), Re-5 H5N1, and H5N3 treated with neem leaf extract, were 80%, 80%, and 60%, respectively, while bivalent vaccine (AI + ND), Re-5 H5N1 and H5N3 without treatment were 60%, 60%, and 40%, respectively. The virus shedding was prevented in groups vaccinated with bivalent vaccine and Re-H5N1 vaccine treated with neem leaf extract, while decreased in the group vaccinated with H5N3 with neem leaf extract and Re-H5N1 without neem leaf extract compared with H5N3, H5N1, and monovalent vaccine. The immunological response after vaccination was stronger in the bivalent vaccine group than in the other commercial vaccine groups treated with neem leaf extract, with geometric mean titer (GMTs) of 315.2 and 207.9 at the third and fourth weeks, respectively. The use of immunostimulant antiviral medicinal plants, such as neem, completely protected chicken flocks against HPAI (H5N8) and prevented AI virus shedding, leading us to the conclusion that the use of bivalent vaccines induces a higher immune response than other different commercial vaccines.

Evidence of the circulation of avian metapneumovirus in domestic backyard chickens in Eastern Saudi Arabia in 2019

Background and Aim

Avian metapneumovirus (aMPV) is a recently discovered respiratory virus in chickens. Avian metapneumovirus has been linked to respiratory syndromes, reproductive failure in affected chickens and turkeys, swollen head syndrome in chickens, and rhinotracheitis in turkeys. Wild birds are considered potential reservoirs of aMPV, particularly aMPV-C. However, little is known about the prevalence of aMPV in Saudi Arabia. Considering the relevance of backyard chickens in the transmission and sustainability of certain avian viral diseases, this study aimed to assess aMPV exposure in backyard chickens and wild birds circulating near selected locations.

Materials and Methods

We collected 368 serum samples from unvaccinated backyard chickens in ten locations in Eastern Saudi Arabia. Furthermore, we collected 78 serum samples from species of free-ranging birds belonging to the Columbidae family, such as pigeons and doves, captured from the same areas. Using commercial enzyme-linked immunosorbent assay kits, we tested the sera of domestic backyard chickens and wild birds for antibodies against aMPV.

Results

Our results showed that 74/368 birds were positive for aMPV-related antibodies. Conversely, none of the tested wild birds seroconverted to aMPV.

Conclusion

The antibody titers detected in the backyard chickens suggested recent exposure to aMPV. Considering these results, further large-scale serological and molecular studies are needed to evaluate the prevalence of aMPV in these birds and characterize the circulating strains of aMPV in this region.

The global prevalence of highly pathogenic avian influenza A (H5N8) infection in birds: A systematic review and meta-analysis

The zoonotic pathogen avian influenza A H5N8 causes enormous economic losses in the poultry industry and poses a serious threat to the public health. Here, we report the first systematic review and meta-analysis of the worldwide prevalence of birds. We filtered 45 eligible articles from seven databases. A random-effects model was used to analyze the prevalence of H5N8 in birds. The pooled prevalence of H5N8 in birds was 1.6%. In the regions, Africa has the highest prevalence (8.0%). Based on the source, village (8.3%) was the highest. In the sample type, the highest prevalence was organs (79.7%). In seasons, the highest prevalence was autumn (28.1%). The largest prevalence in the sampling time was during 2019 or later (7.0%). Furthermore, geographical factors also were associated with the prevalence. Therefore, we recommend site-specific prevention and control tools for this strain in birds and enhance the surveillance to reduce the spread of H5N8.

Selenium nanoparticles enhance the efficacy of homologous vaccine against the highly pathogenic avian influenza H5N1 virus in chickens

A proper vaccination against avian influenza viruses in chicken can significantly reduce the risk of human infection. Egypt has the highest number of recorded humans highly pathogenic avian influenza (HPAI)-H5N1 infections worldwide despite the widespread use of homologous vaccines in poultry. Enhancing H5N1 vaccine efficacy is ultimately required to better control HPAI-H5N1. The aim of this study is to boost chicken immunity by combined with inactivated HPAI-H5N1 with selenium nanoparticles (SeNPs). The chickens groups 1-3 were fed diets supplemented with SeNPs concentrations (0.25, 0.5, and 1 mg/kg) for 3 weeks and then vaccinated (inactivated HPAI-H5N1). while groups 4,5 and 6 were fed with SeNPs free diets and administered with 0.5 ml of the vaccine combined with 0.02, 0.06, and 0.1 mg/dose of SeNPs and then all groups were challenged with homologous virus 3 weeks post-vaccination (WPV). Group 7, 8 were used as control positive and negative respectively. At 4, 5, and 6 WPV, antibody titer was considerably higher in the group fed a meal supplemented with 1 mg SeNPs/kg. In contrast, both methods of SeNPs supplementation significantly increased the Interleukin 2 (IL2), Interleukin 6 (IL6), and Interferon γ (IFNγ) expressions in the blood cells in a dose-dependent manner, with a higher expression observed in the group that was vaccinated with 0.1 mg/dose. After the challenge, all groups that received SeNPs via diet or vaccines dose showed significant reduction in viral shedding and milder inflammation in lung, trachea, spleen, and liver in addition to higher expression of IL2, IL6, and IFNγ, with the highest expression observed in the group that was vaccinated with 0.1 mg/dose compared the plain vaccinated group. The groups of 1 mg SeNPs/kg and combined vaccinated with 0.1 mg/dose showed the best vaccine efficacy. However, the group vaccinated with 0.1 mg/dose showed the earliest reduction in viral shedding. Overall, SeNPs supplementation in the diet and the administration of the vaccine formula with SeNPs could enhance vaccine efficacy and provide better protection against HPAI-H5N1 in chickens by enhancing cellular immunity and reducing inflammation. We recommend using SeNPs as a vaccine combination or feeding with diet to increase the immunity and vaccine efficacy against H5N1.

Pathological analysis and genetic characterization of the first outbreak H5N8 subtype avian influenza virus isolated from wild swan in Shandong, China

In January 2021, an outbreak of H5N8 subtype avian influenza was identified from wild mute swans (Cygnus olor) in an overwintering site located within Yellow River Delta Nature Reserve in Shandong, China, for the first time. We sequenced the hemagglutinin (HA) and neuraminidase (NA) genome segments of the virus, named A/mute swan/Shandong/1/2021 (H5N8), and explored the genetic characterization and comparative phylogenetic analysis to track its origin. The wild swans prior to death showed nervous signs accompanied by a twisted neck. The major pathological changes of the heart, lung, trachea, kidney, spleen, and glandular stomach were hemorrhage, and extensive necrotic lesions in the liver and pancreas were also observed. Further analysis of the HA and NA phylogenetic trees generated by H5N8 strains isolated worldwide revealed that the isolate has a close genetic relationship with the H5N8 subtype avian influenza virus (AIV) recently isolated in Korea and Japan from 2020 to 2021, suggesting the potential role of mute swans in the global dissemination of the H5N8 subtype AIVs along the migration routes. Therefore, enhanced active surveillance in wild and domestic birds is required to monitor the introduction and spread of the H5N8 subtype AIV by migratory birds in order to decrease the risk of H5N8 outbreaks.

Discrepancies in the efficacy of H5 inactivated avian influenza vaccines in specific-pathogen-free chickens against challenge with the Egyptian H5N8 clade 2.3.4.4 Group B virus isolated in 2018

BACKGROUND AND AIM

Highly pathogenic avian influenza H5N8 virus of clade 2.3.4.4 was newly emerged to Egypt and firstly detected in carcasses of wild birds in November 2016. This study assessed the protection efficacy and virus shedding reduction of three different inactivated avian influenza (AI) H5 (H5N1, H5N2, and H5N3) commercial vaccines against challenge with two newly emerging highly pathogenic AI virus H5N8 Egyptian isolates in specific-pathogen-free (SPF) chicks.

MATERIALS AND METHODS

10-day-old SPF chicks (n=260) were divided into 20 groups (n=13). Groups 1-5 were vaccinated through the subcutaneous route (S/C) with 0.5 mL of H5N1 vaccine, Groups 6-10 were vaccinated (S/C) with 0.5 mL of H5N2 vaccine, and Groups 11-15 were vaccinated (S/C) with 0.5 mL of H5N3 vaccine. Positive control groups (16-19) were challenged at 25 and 31 days old (2 and 3 weeks post-vaccination [PV]) using H5N8 clade 2.3.4.4 A/duck/Egypt/F13666A/2017(H5N8) and H5N8 clade 2.3.4.4 A/chicken/Egypt/18FL6/2018(H5N8). Group 20 was left non-vaccinated as a control. All vaccinated groups were divided and challenged with both viruses at 25 and 31 days of age. The viral challenge dose was 0.1 mL of 106 EID50/0.1 mL titer/chick, and it was administered oronasally. All chicks were kept in isolators for 14 days after each challenge. Sera samples were collected weekly and at 2 weeks post-challenge (PC) to detect a humoral immune response. PC mortalities were recorded daily for 10 days to calculate the protection percentages. Tracheal swabs were collected from the challenged chicks in different groups at 3, 5, 7, and 10 days PC. Kidneys and spleens were collected at 3, 5, 7, and 10 days PC and kept in formalin for histopathological examination to assess lesions and severity scores. Tracheal swabs were inoculated in 10-day-old SPF embryonated chicken eggs for virus titration and to calculate shedding levels.

RESULTS

All studied vaccines displayed 70-100% protection within 10 days PC. Hemagglutination inhibition results from sera samples revealed antibody titers ranging from 0.6 to 5.4 log2 starting at 1-week PV with the highest titers at 4 weeks PV. Challenged SPF chickens exhibited a notable reduction in virus shedding, with an average of 1.5-2 log10, compared to control birds. Various histopathological lesions with different scores were detected.

CONCLUSION

Our findings suggest that the inadequate virus shedding reduction and protection efficacy of studied vaccines were variable and that the type of vaccine to be used under field conditions should be reconsidered. Study of the variability between the Egyptian old emerged AI (AIV) 2017 H5N8 strains and the new emerging AIV 2018 H5N8 is required to achieve optimal protection and limit the current economic losses.