Genetic Characterization and Pathological Evaluation of Clade 2.3.4.4b Avian Influenza Virus(H5N8) in Naturally Infected Domestic Ducks in Egyptian Farms
Genetic Characterization and Pathological Evaluation of Clade 2.3.4.4b Avian Influenza Virus(H5N8) in Naturally Infected Domestic Ducks in Egyptian Farms
Sara Magdy Hashim1, Elshaimaa Ismael2, Mohamed Tarek3, Faten Fathy Mohammed1*, Fatma Amer Abdel Reheem3, Rawhia Esawy Doghaim1
ABSTRACT
The highly pathogenic avian influenza (HPAI) H5N8 virus causes severe economic deficit in the poultry production in Egyptian farms and has a potential intimidate for the public health, this subtype firstly was detected in Egypt in 2016 from wild birds. In the present study, samples were collected from 100 Egyptian domestic ducks of different ages from seven Egyptian governorates from period 2018 to 2020. Tissue specimens were allocated for HPAI H5N8 diagnosis using rRT-PCR and the results were 66 positive samples with the highest incidence in the Giza governorate. The winter season showed the highest incidence with 28 positive samples. For more characterization, the full HA gene was sequenced, followed by phylogenetic analysis according to the year examined, mortality rate, positive results of RT- qPCR with low Ct value (H5 and N8 were 15 and 20 respectively). The phylogenetic tree revealed that H5N8 field isolate clustering in clade 2.3.4.4b. The histopathological hallmarks, in H5N8 naturally infected ducks, included acute inflammatory, necrotic and vascular reactions that involve different tissues. The immunohistochemical characterization of viral antigen revealed direct relation between viral residence in tissue and developed pathology. The present study confirmed that H5N8 HPAI clade 2.3.4.4b, became a predominant strain during the period 2018-2020, causing severe outbreaks in duck farms in Egypt.
Keywords | Avian influenza, HPAI, H5N8, Ducks, Pathology, Egypt.
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