الفهرس 
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Abstract
Emerging clade 2.3.4.4 of the highly pathogenic avian influenza (HPAI) virus strain H5N8 in Egypt started to affect wild bird in late 2016. The virus was spread to backyard and commercial poultry of many governorates. In the present study, we tested clade 2.3.2 H5-recombinant baculovirus vaccine to evaluate mortality, clinical signs, virus shedding and histopathological changes after experimental infection of Muscovy and Pekini ducks with the clade 2.3.4.4b HPAI H5N8 virus (A/common-coot/Egypt/CA285/2016). The results revealed that, the mortality rate in Muscovy and Pekini ducks, which vaccinated once at 10-days of age and challenged at 31-days of age, were 10% and 0% Vs. 40% and 0% in non-vaccinated challenged ducks, respectively. Whereas, in group vaccinated twice at 10 and 28-days of age and challenged at 49-days, were 0% Vs. 60% and 40% in non-vaccinated challenged ducks, respectively. However, Muscovy ducks showed more severe clinical signs and gross lesions than Pekini ducks. In addition, tracheal viral shedding in Muscovy and Pekini ducks, which vaccinated once and challenged was 50%; 22%; and 0% Vs 100 % in challenged non-vaccinated ducks at 3, 5 and 7-days post-challenge (dpc), respectively. While, viral shedding in Muscovy and Pekini ducks, vaccinated twice and challenged, was 0% at 3, 5 and 7-dpc Vs. 100% in non-vaccinated challenged ducks, respectively. Indeed, the H5-baculovirus-based vaccine could be used in ducks with better vaccination regime based on double-dose vaccination at 10 and 28 days of age.