H9N2 avian influenza viruses have become globally widespread in poultry over the last two decades and represent a genuine threat both to the global poultry industry but also humans through their high rates of zoonotic infection and pandemic potential. H9N2 viruses are generally hyperendemic in effected countries and have been found in poultry in many new regions in recent years. In this review we examine the current global spread of H9N2 avian influenza viruses as well as their host range, tropism, transmission routes and the risk posed by these viruses to human health.

Influenza is a disease that poses a significant health burden worldwide. Vaccination is the best way to prevent influenza virus infections. However, conventional vaccines are only effective for a short period of time due to the propensity of influenza viruses to undergo antigenic drift and antigenic shift. The efficacy of these vaccines is uncertain from year-to-year due to potential mismatching between the circulating viruses and vaccine strains, mutations arising due to egg adaptation, and potential contamination of the vaccine virus stock. Subsequently, the inability to store these vaccines long-term and vaccine shortages are challenges that need to be overcome. Conventional vaccines are also less effective for certain populations, including the young, old, and immunocompromised. This warrants for diverse efficacious vaccine developmental approaches, involving both active and passive immunization. As opposed to active immunization platforms (requiring the use of whole or portions of pathogens as vaccines), the rapidly developing passive immunization involves administration of either pathogen-specific or broadly acting antibodies against a kind or class of pathogens as a prophylactic treatment to corresponding acute infection. Several antibodies with broadly acting capacities have been discovered that may serve as means to suppress influenza viral infection and allow the process of natural immunity to engage opsonized pathogens whilst boosting immune system by antibody-dependent mechanisms that bridge the innate and adaptive arms. By that, passive immunotherapeutics approach assumes a robust tool that could aid control of influenza viruses. In this review, we comment on some improvements in influenza management and promising vaccine development platforms, with emphasis on the capacity of passive immunotherapeutics especially when coupled with the use of antivirals in the management of influenza infection.

Newcastle disease virus (NDV) genotype VII is a highly pathogenic Orthoavulavirus that has caused multiple outbreaks among poultry in Egypt since 2011. This study aimed to investigate the genetic diversity of NDV prevailing in domestic and wild birds in Egyptian governorates. A total of 37 oropharyngeal swabs from wild birds and 101 swabs from domestic bird flocks including chickens, ducks, turkeys, and swans were collected from different geographic regions within 13 governorates during 2019-2020. Virus isolation and propagation via embryonated eggs revealed 91 swab samples produced allantoic fluid containing hemagglutination activity, suggestive of virus presence. The use of RT-PCR targeted to F gene successfully detected NDV in 85 samples. The geographical prevalence of NDV spread to 12 governorates in domestic birds, migratory and non-migratory wild birds. Following whole genome sequencing, we assembled six NDV genome sequences (70 - 99% of genome coverage), including five full F gene sequences. All NDV strains carried high virulence, based on the presence of polybasic amino acids (RRQRF) at the F gene cleavage site. Phylogenetic analysis revealed that the NDV strains belonged to class II within genotype VII.1.1. The presence of genetically similar virulent NDV in wild birds further highlights their role in the dissemination of NDV in poultry populations across Egypt. Continued genomic surveillance in both wild birds and poultry would be necessary for monitoring NDV incursions and genetic diversification.

Pigeon paramyxovirus serotype 1 (PPMV-1), primarily originating from racing pigeons, has become a global panzootic, spreading to poultry and wild birds, thus posing a threat to the poultry industry. Egypt uses both inactivated pigeon paramyxovirus (PPMV-1) and conventional Newcastle disease virus (NDV) vaccines to protect pigeons. However, the impact of prevalent strains and the effectiveness of available vaccines in pigeons in Egypt are unclear. This study investigates the virulence of PPMV-1 isolated from vaccinated pigeons in Sharkia, Egypt (Pigeon/ Egypt/Sharkia-19/2015/KX580988). Ten-day-old specific-pathogen-free embryonated chicken eggs infected with this strain exhibited a mean death time (MDT) of 86.4±5.88 hours. The intracerebral pathogenicity index (ICPI) in day-old chicks was 0.8, while pigeons experienced an ICPI of 0.96 and an intravenous pathogenicity index (IVPI) of 2.11. These findings classify the strain as virulent and velogenic. Experimental infection with this PPMV-1 strain at 106 EID50/0.1 ml resulted in a 62.5% mortality rate in pigeons, displaying nervous and enteric distress. The virus caused extensive lesions in visceral organs, with strong immunohistochemistry signals in all examined organs, indicating the systemic spread of the virus concurrent to its neurotropic and viscerotropic tropism. Furthermore, vaccination using inactivated PPMV-1 and live NDV LaSota vaccine regimen protected 100% of pigeons against mortality, while a single NDV LaSota vaccine provided 62.5% protection. The PPMV alone or combined with NDV LaSota induced protective levels of hemagglutination inhibition antibody titers and reduced virus shedding from buccal and cloacal cavities. These findings suggest that using both inactivated PPMV-1 (G-VI) and live attenuated NDV (LaSota) vaccines is an effective prophylactic regimen for preventing and controlling PPMV-1 and NDV in pigeons, thereby reducing the risk of interspecies transmission.

Outbreaks of avian pathogens such as Newcastle disease virus, avian influenza virus and Salmonella have a major impact on economies and food security worldwide. Some pathogens also pose a significant zoonotic potential, especially avian influenza viruses. Vaccination plays a key role in controlling many poultry diseases and there are many vaccines licenced in the United Kingdom for diseases of poultry caused by viruses, bacteria, and parasites. However, these vaccines often do not provide complete protection and can cause unwanted side effects. Several factors affect the potency of poultry vaccines including the type of vaccination used, the mechanism of delivery and the use of adjuvants. Advancements in technology have led to the study and development of novel vaccines and vaccine adjuvants for use in poultry. These induce stronger immune responses compared to current vaccine technology and have the potential to protect against multiple poultry diseases. This review aims to discuss existing poultry vaccine technology, the effect of delivery mechanisms of vaccine efficacy, the use of current and novel adjuvants, the ability to target antigen to antigen presenting cells, the use of probiotics, multivalent vaccines, and nanotechnology to enhance the potency of poultry vaccines.

Hydropericardium hepatitis syndrome (HHS) caused by fowl adenovirus-4 have been frequently reported in commercial chickens from several countries causing significant economical losses. In Azerbaijan, fowl adenovirus infections in broiler and layer breeders flocks cause severe disease and mortality. Here we investigated the pathological lesions and the dissemination of fowl adenovirus-4 into the visceral organs of infected birds. Tissue samples containing liver, heart and spleen from 20 necropsied chickens were collected on the FTA cards and presence of fowl adenovirus was analysed by PCR and sequencing. Postmortem findings of both broiler and layer breeder chickens were similar, and the most affected organs were the liver with hepatitis and the heart with hydropericardium lesions. Other postmortem signs include swollen kidneys with haemorrhages and small white foci on the surface of the spleens. In some birds intestinal congestion and ecchymotic hemorrhages were also apparent. The PCR analysis revealed that all collected organs from 20 birds showed presence of fowl adenovirus-4 genome. The sequence analysis showed that fowl adenovirus-4 prevalent in Azerbaijan carry more closer phylogenetic relationship with the viruses prevalent in the Middle East, Far East and Indian subcontinent. However, a distinct diversity was seen from the strains prevalent in Europe, North and South America. This study will provide evidence the impact of fowl adenovirus-4 on the poultry production and improved preventive disease control strategies are required to reduce the HHS disease in chickens in Azerbaijan.