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Ahmed Ali

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Open access Aug 2026

Protective Efficacy Evaluation of Various Inactivated Vaccines Against the Newly Circulated Highly Pathogenic Avian Influenza Virus H5N1 of Clade 2.3.4.4b in Pekin Ducks

Highly pathogenic avian influenza (HPAI) virus H5N1of clade 2.3.4.4b has emerged as the predominant lineage circulating in poultry flocks worldwide, raising concerns regarding the protective efficacy of currently available commercial vaccines, particularly in domestic ducks, which play an important role in virus maintenance and transmission. Thus, this study evaluated the immunogenicity along with the protective efficacy of four inactivated H5 vaccines against a recently isolated local HPAI-H5N1 (Newvalley-3-H5N1-2024, clade 2.3.4.4b) strain in Pekin ducks in Egypt. A total of 150 seronegative ducks were divided into vaccinated and control groups (10 groups) and vaccinated at 10 days of age. At 31 days of age, the vaccinated and positive control groups were challenged using 106.5 EID50/0.5 mL/duck with the local isolate (Newvalley-3-H5N1-2024) via the oculo-nasal route. The vaccine efficacy was assessed through clinical signs, survival rate, hemagglutination inhibition (HI) antibody titer, tracheal and cloacal viral shedding quantified by real-time RT-PCR, and histopathological examination of trachea, lung, pancreas, and brain tissues. Generally, all ducks vaccinated with the ValleyVac Avian Flu H5 plus and MEFLUVACTM H5 PLUS 8 showed a significantly higher survival rate (100%) at 10 days post-vaccination (DPV) than those in the positive control (66.7% mortality rate). In contrast, ducks exhibited mortality rates ranging from 6.7% in the SERVAC Flu H5N1 group to 13.4% in the Sinder Fluvac group. The ValleyVac Avian Flu H5 plus and MEFLUVAC™ H5 PLUS 8 vaccines induced the highest HI antibody titers at 7, 14, 21, and 28 DPV in both homologous and heterologous AIV antigens, resulting in a significant reduction in viral load among all vaccinated duck groups (p-value < 0.05) comparable to the positive control group. Conversely, the SERVAC Flu H5N1 and Sinder Fluvac vaccines provided partial protection, suboptimal immunogenicity at different time points, and elevated viral shedding. Histopathological findings in ValleyVac Avian Flu H5 plus and MEFLUVAC™ H5 PLUS 8 vaccines exhibited mild tissue alterations following AIV challenge. Marked pathological lesions were observed in the SERVAC Flu H5N1 and Sinder Fluvac vaccinated groups. Among tested vaccines, both ValleyVac Avian Flu H5 plus and MEFLUVACTM H5 PLUS 8 showed the highest level of protective efficacy against the circulating AIV strain compared with other commercial vaccines. This study highlights the need for continuous molecular surveillance, antigenic matching, and regular updating of vaccine seed strains to ensure efficient HPAI control in Egypt.

Eman Abd El Menum Shosha, I. Eldaghayes, Ahmed A. H. Ali et al. · 0 citations
Open access Jul 2026

Global transmission pathways and adaptive molecular evolution of avian infectious bronchitis GI-23 (Variant 2)

The infectious bronchitis virus (IBV) causes significant losses in commercial poultry egg and meat production. Since its first emergence, the genotype GI-23 (Variant 2) has progressively increased its geographical distribution, shown a significant virulence, and challenged the vaccine efficacy. Global viral transmission could be attributed to multiple factors including human related activities such as poultry and vaccine trades while other contributing factors such as the role of wild birds cannot be neglected. Therefore, A total 260 full S1 GI-23 sequences were obtained from Genebank, structured and intensively analyzed. The recombination analyses were conducted using RDP5 and GARD on the total dataset to identify the possible recombinant events. The recombinant-free dataset (214 sequences) was phylogeographically analyzed using BEAST 1.10, then selection pressure analyses to identify the possible migration routes and selection pressure markers, respectively. Recombination analyses showed multiple internal recombination events in 17.6% of the sequences. Phylogeographic analysis suggested Central and Eastern European (CEE) countries (i.e., particularly Poland and Romania) as likely sources of American GI-23-like virus outbreaks. Interestingly, the selection pressure analyses indicated positive selection signals, identifying five codons in some previously distinguished critical positions such as 61, 94, 119, 127, and 197. The virus extended geographical spread as well as molecular evolution through recombination and positive selection in the spike gene poses a major concern for increased adaptation and enhanced pathogenicity in susceptible domesticated and probably wild birds. Further studies on the impact of both recombination events and the identified positive selection codons are highly recommended to elucidate the molecular evolution mechanisms of IBV GI-23.

Mohamed H Houta, G. Franzo, A. El-Sawah et al. · 0 citations

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