Pathomolecular characterization of recently isolated duck Astrovirus from domestic ducklings in Egypt

Astrovirus infection significantly impacts poultry production due to its fatal effect on young birds and their ability to be transmitted by horizontal and vertical routes. In the current study, eight Egyptian duckling farms from different breeds (Moulard, Muscovy, and Pekin) with a history of sudden death accompanied by neurological signs with marked hepatitis lesions at Al-Qalyubia, Al-Sharqia, and Assuit governorates from 2022 to 2023 have been investigated. All the examined freshly dead ducklings have a history of vaccination with the live attenuated duck hepatitis vaccine. During the laboratory investigations, DAstV was successfully isolated on the chorioallantoic membrane (CAM) of specific pathogen-free (SPF) embryonated chicken eggs (ECE) and designated as DAstV- VSVRI-CLEVB-2022 and showed the characteristic star-shaped six-point end of astrovirus when examined under the electron microscope. Molecular identification showed positive PCR amplification targeting the 434 bp of the ORF1b encoding non-structural proteins and is highly conserved of the G4260 Avastrovirus 2, sequence analysis showed that the isolated strain showed 100% similarity with duck astrovirus strain HBGT-China-2014 (KX290465.1). Pathogenicity testing of the isolated astrovirus in susceptible one-day-old ducklings, showed typical death signs of astrovirus at 31, 38, and 50 h post-infection (PI) with paint brush hemorrhagic liver surface. The above-mentioned results showed that DAstV could be one of the causative agents of acute duck hepatitis in Egypt and further investigations are recommended to prepare a local autogenous vaccine from the isolated strain with the application of strict biosecurity measures and evaluate its efficacy against the field challenge to control such a problem.