A comprehensive review of highly pathogenic avian influenza (HPAI) H5N1: An imminent threat at doorstep

The Alarming Situation of Highly Pathogenic Avian Influenza Viruses in 2019-2023

Avian influenza viruses (AIVs) have the potential to cause severe illness in wild birds, domestic poultry, and humans. The ongoing circulation of highly pathogenic avian influenza viruses (HPAIVs) has presented significant challenges to global poultry industry and public health in recent years. This study aimed to elucidate the circulation of HPAIVs during 2019 to 2023. Specifically, we assess the alarming global spread and continuous evolution of HPAIVs. Moreover, we discuss their transmission and prevention strategies to provide valuable references for future prevention and control measures against AIVs.

Highly pathogenic avian influenza A(H5N1) in animals: A systematic review and meta-analysis

Introduction

Avian influenza A H5N1 is a significant global public health threat. Although relevant, systematic reviews about its prevalence in animals are lacking.

Methods

We performed a systematic literature review in bibliographic databases to assess the prevalence of H5N1 in animals. A meta-analysis with a random-effects model was performed to calculate the pooled prevalence and 95 % confidence intervals (95%CI). In addition, measures of heterogeneity (Cochran's Q statistic and I2 test) were reported.

Results

The literature search yielded 1359 articles, of which 33 studies were fully valid for analysis, including 96,909 animals. The pooled prevalence for H5N1 in birds (n = 90,045, 24 studies) was 5.0 % (95%CI: 4.0-6.0 %; I2 = 99.21); in pigs (n = 3,178, 4 studies) was 1.0 % (95%CI: 0.0-1.0 %); in cats (n = 2,911, 4 studies) was 0.0 % (95%CI: 0.0-1.0 %); and in dogs (n = 479, 3 studies) was 0.0 % (95%CI: 0.0-2.0 %).

Conclusions

While the occurrence of H5N1 in animals might be comparatively limited compared to other influenza viruses, its impact on public health can be substantial when it transmits to humans. This virus can potentially induce severe illness and has been linked to previous outbreaks. Therefore, it is essential to closely monitor and comprehend the factors influencing the prevalence of H5N1 in both avian and human populations to develop effective disease control and prevention strategies.

Exploring Potential Intermediates in the Cross-Species Transmission of Influenza A Virus to Humans

The influenza A virus (IAV) has been a major cause of several pandemics, underscoring the importance of elucidating its transmission dynamics. This review investigates potential intermediate hosts in the cross-species transmission of IAV to humans, focusing on the factors that facilitate zoonotic events. We evaluate the roles of various animal hosts, including pigs, galliformes, companion animals, minks, marine mammals, and other animals, in the spread of IAV to humans.

Pinnipeds and avian influenza: a global timeline and review of research on the impact of highly pathogenic avian influenza on pinniped populations with particular reference to the endangered Caspian seal (Pusa caspica)

This study reviews chronologically the international scientific and health management literature and resources relating to impacts of highly pathogenic avian influenza (HPAI) viruses on pinnipeds in order to reinforce strategies for the conservation of the endangered Caspian seal (Pusa caspica), currently under threat from the HPAI H5N1 subtype transmitted from infected avifauna which share its haul-out habitats. Many cases of mass pinniped deaths globally have occurred from HPAI spill-overs, and are attributed to infected sympatric aquatic avifauna. As the seasonal migrations of Caspian seals provide occasions for contact with viruses from infected migratory aquatic birds in many locations around the Caspian Sea, this poses a great challenge to seal conservation. These are thus critical locations for the surveillance of highly pathogenic influenza A viruses, whose future reassortments may present a pandemic threat to humans.

Natural Infection with Highly Pathogenic Avian Influenza A/H5N1 Virus in Pet Ferrets

The study involved five ferrets from one household in Poland, comprising three sick 9-week-old juveniles, their healthy mother, and another clinically normal adult, admitted to the veterinary clinic in June 2023. The juvenile ferrets displayed significant lethargy and a pronounced unwillingness to move with accompanying pulmonary distress. Prompted by concurrent outbreaks of A/H5N1 influenza virus infections in Polish cats, point-of-care tests were conducted that revealed type A influenza antigens in the throat swabs of all five ferrets. Despite treatment, one juvenile ferret exhibited dyspnea and neurological symptoms and eventually died. The two remaining ferrets recovered fully, including one severely affected showing persistent dyspnea and incoordination without fever that recovered after 11 days of treatment. In the RT-qPCR, the throat swabs collected from all surviving ferrets as well as the samples of lungs, trachea, heart, brain, pancreas, liver, and intestine of the succumbed ferret were found positive for A/H5N1 virus RNA. To our best knowledge, this is the first documented natural A/H5N1 avian influenza in domestic ferrets kept as pets. In addition, this outbreak suggests the possibility of asymptomatic A/H5N1 virus shedding by ferrets, highlighting their zoonotic potential and the advisability of excluding fresh or frozen poultry from their diet to reduce the A/H5N1 virus transmission risks.

H5N1 clade 2.3.4.4b avian influenza viruses replicate in differentiated bovine airway epithelial cells cultured at air-liquid interface

Highly pathogenic avian influenza (HPAI) H5N1 viruses are responsible for disease outbreaks in wild birds and poultry, resulting in devastating losses to the poultry sector. Since 2020, an increasing number of outbreaks of HPAI H5N1 was seen in wild birds. Infections in mammals have become more common, in most cases in carnivores after direct contact with infected birds. Although ruminants were previously not considered a host species for HPAI viruses, in March 2024 multiple outbreaks of HPAI H5N1 were detected in goats and cattle in the United States. Here, we have used primary bronchus-derived well-differentiated bovine airway epithelial cells (WD-AECs) cultured at air-liquid interface to assess the susceptibility and permissiveness of bovine epithelial cells to infection with European H5N1 virus isolates. We inoculated bovine WD-AECs with three low-passage HPAI clade 2.3.4.4b H5N1 virus isolates and detected rapid increases in viral genome loads and infectious virus during the first 24 h post-inoculation, without substantial cytopathogenic effects. Three days post-inoculation infected cells were still detectable by immunofluorescent staining. These data indicate that multiple lineages of HPAI H5N1 may have the propensity to infect the respiratory tract of cattle and support extension of avian influenza surveillance efforts to ruminants. Furthermore, this study underscores the benefit of WD-AEC cultures for pandemic preparedness by providing a rapid and animal-free assessment of the host range of an emerging pathogen.

H5N1 high pathogenicity avian influenza virus in migratory birds exhibiting low pathogenicity in mallards increases its risk of transmission and spread in poultry

In 2020, an H5N1 avian influenza virus of clade 2.3.4.4b was detected in Europe for the first time and was spread throughout the world by wild migratory birds, resulting in the culling of an unprecedented number of wild birds and poultry due to the epidemic. In February 2023, we isolated and identified a strain of H5N1 high pathogenicity avian influenza virus from a swab sample from a grey crane in Ningxia, China. Phylogenetic analysis of the Hemagglutinin (HA) gene showed that the virus belonged to clade 2.3.4.4b, and several gene segments were closely related to H5N1 viruses infecting humans in China. Analysis of key amino acid sites revealed that the virus contained multiple amino acid substitutions that facilitate enhanced viral replication and mammalian pathogenicity. The results of animal challenge experiments showed that the virus is highly pathogenic to chickens, moderately pathogenic to BALB/c mice, and highly infectious but not lethal to mallards. Moreover, the virus exhibited minor antigenic drift compared with the H5-Re14 vaccine strain. To this end, we need to pay more attention to the monitoring of wild birds to prevent further spread of viruses to poultry and mammals, including humans.

Stability and Detection Limit of Avian Influenza, Newcastle Disease Virus, and African Horse Sickness Virus on Flinders Technology Associates Card by Conventional Polymerase Chain Reaction

The Flinders Technology Associates (FTA) card, a cotton-based cellulose membrane impregnated with a chaotropic agent, effectively inactivates infectious microorganisms, lyses cellular material, and fixes nucleic acid. The aim of this study is to assess the stability and detection limit of various RNA viruses, especially the avian influenza virus (AIV), Newcastle disease virus (NDV), and African horse sickness virus (AHSV), on the FTA card, which could significantly impact virus storage and transport practices. To achieve this, each virus dilution was inoculated onto an FTA card and stored at room temperature in plastic bags for durations ranging from 1 week to 6 months. Following storage, the target genome was detected using conventional reverse transcription polymerase chain reaction. The present study demonstrated that the detection limit of AIV ranged from 1.17 to 6.17 EID50 values over durations ranging from 1 week to 5 months, while for NDV, it ranged from 2.83 to 5.83 ELD50 over the same duration. Additionally, the detection limit of AHSV was determined as 4.01 PFU for both 1 and 2 weeks, respectively. Based on the demonstrated effectiveness, stability, and safety implications observed in the study, FTA cards are recommended for virus storage and transport, thus facilitating the molecular detection and identification of RNA viral pathogens.

A computational approach to design a multiepitope vaccine against H5N1 virus

Since 1997, highly pathogenic avian influenza viruses, such as H5N1, have been recognized as a possible pandemic hazard to men and the poultry business. The rapid rate of mutation of H5N1 viruses makes the whole process of designing vaccines extremely challenging. Here, we used an in silico approach to design a multi-epitope vaccine against H5N1 influenza A virus using hemagglutinin (HA) and neuraminidase (NA) antigens. B-cell epitopes, Cytotoxic T lymphocyte (CTL) and Helper T lymphocyte (HTL) were predicted via IEDB, NetMHC-4 and NetMHCII-2.3 respectively. Two adjuvants consisting of Human β-defensin-3 (HβD-3) along with pan HLA DR-binding epitope (PADRE) have been chosen to induce more immune response. Linkers including KK, AAY, HEYGAEALERAG, GPGPGPG and double EAAAK were utilized to link epitopes and adjuvants. This construct encodes a protein having 350 amino acids and 38.46 kDa molecular weight. Antigenicity of ~ 1, the allergenicity of non-allergen, toxicity of negative and solubility of appropriate were confirmed through Vaxigen, AllerTOP, ToxDL and DeepSoluE, respectively. The 3D structure of H5N1 was refined and validated with a Z-Score of - 0.87 and an overall Ramachandran of 99.7%. Docking analysis showed H5N1 could interact with TLR7 (docking score of - 374.08 and by 4 hydrogen bonds) and TLR8 (docking score of - 414.39 and by 3 hydrogen bonds). Molecular dynamics simulations results showed RMSD and RMSF of 0.25 nm and 0.2 for H5N1-TLR7 as well as RMSD and RMSF of 0.45 nm and 0.4 for H5N1-TLR8 complexes, respectively. Molecular Mechanics Poisson-Boltzmann Surface Area (MM/PBSA) confirmed stability and continuity of interaction between H5N1-TLR7 with the total binding energy of - 29.97 kJ/mol and H5N1-TLR8 with the total binding energy of - 23.9 kJ/mol. Investigating immune response simulation predicted evidence of the ability to stimulate T and B cells of the immunity system that shows the merits of this H5N1 vaccine proposed candidate for clinical trials.

Simultaneous Differential Detection of H5, H7, H9 and Nine NA Subtypes of Avian Influenza Viruses via a GeXP Assay

H5, H7 and H9 are the most important subtypes of avian influenza viruses (AIVs), and nine neuraminidase (NA) subtypes (N1-N9) of AIVs have been identified in poultry. A method that can simultaneously detect H5, H7, H9 and the nine NA subtypes of AIVs would save time and effort. In this study, 13 pairs of primers, including 12 pairs of subtype-specific primers for detecting particular subtypes (H5, H7, H9 and N1-N9) and one pair of universal primers for detecting all subtypes of AIVs, were designed and screened. The 13 pairs of primers were mixed in the same reaction, and the 13 target genes were simultaneously detected. A GeXP assay using all 13 pairs of primers to simultaneously detect H5, H7, H9 and the nine NA subtypes of AIVs was developed. The GeXP assay showed specific binding to the corresponding target genes for singlet and multiplex templates, and no cross-reactivity was observed between AIV subtypes and other related avian pathogens. Detection was observed even when only 102 copies of the 13 target genes were present. This study provides a high-throughput, rapid and labor-saving GeXP assay for the simultaneous rapid identification of three HA subtypes (H5, H7 and N9) and nine NA subtypes (N1-N9) of AIVs.