Summary Duck hepatitis A viruses (DHAV-1, DHAV-2, and DHAV-3) are the predominant cause of duck virus hepatitis (DVH), a disease of ducklings that leads to massive morbidities, mortalities, and economic losses. As a duck-producing-country, Egypt suffered lately from several attacks of DVH, despite the regular vaccination of birds. Between spring 2016 and summer 2018, 54 duckling flocks in the Sharkia province of Egypt were tested using the reverse transcription PCR (RT-PCR) based on the DHAV-3D targeting primers. Of them, 27.8% (15/54) were positive. Upon retesting of positive samples using RT-PCR and DHAV-3 VP1 based primers, 33.3% (5/15) contained DHAV-3 RNA. For further analysis at the molecular level, the VP1 and the 3D genes were sequenced using the same primer sets used earlier. The phylogenetic trees confirmed that study sequences belonged to DHAV-3. However, they were displayed as a sperate cluster following a geographically-dependent distribution. They were also completely unrelated to the Egyptian DHAV-1 based vaccine. This was further confirmed by low nucleotide and amino acid identities in relation to this vaccine. In addition, the VP1 and 3D genes had the same phylogenetic topography. The study VP1 sequences had 3 unique aa substitutions (L59, V208 only in one strain, and C219). As far as we know, this is the first report on DHAV-3 outside Asia, particularly in Egypt. Accordingly, the vaccination strategy against DHAV should be quickly updated to avoid further dissemination of the virus. The epidemiology, pathogenicity, and evolution of DHAV-3 should be carefully monitored in Egypt.
First report on duck hepatitis A virus 3 from duckling flocks of Egypt
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Tamer I. R. Hassan, Amal Eid, Ibrahim A. I. Ghanem, Abeer M. Shahin, Samy A. A. Adael, Fakry F. Mohamed; First report on duck hepatitis A virus 3 from duckling flocks of Egypt. Avian Dis doi: https://doi.org/10.1637/aviandiseases-D-19-00158
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