Isolation and Identification of a New Duck Adenovirus B2 with Insertion and Deletion Mutations

  Objective   A previously unknown strain of duck adenovirus B2 (DAdV B2) was isolated from a ducking of pale liver disease in Fujian and identified for epidemiological reference.

  Methods   The virus associated with the disease was detected by PCR and isolated for identification by genome sequencing and a challenge test.

  Result  The DAdV B2/BG48 virus infected LMH cells in the duck became swollen like a ballon, and eventually, died and disintegrated. The MDEF cells inoculated with the isolate changed from a spindle-shape to ball-like and clustered together with intercellular spaces in between. Distinctively, BG48 genome had a 3 bp insertion in the pX region, a 33 bp insertion in the ORF19B domain, and 42 bp deletion at the junction between ORF64 and ORF67. A G-base was found on the 133^rd spot after the starting code of ORF67 and no truncated mutation in the terminal nor other codes compared with CH-GD-12-2014, or BG27 and BG18 previously identified. In a challenge test, BG48 induced a 50% morbidity and 0 mortality on 2-day-old Muscovy ducks with similar clinical symptoms and pathological changes between the artificially infected and the naturally diseased birds.

  Conclusion  A novel DAdV B2 strain, BG48, from a Muscovy duck of pale liver disease was isolated and identified. The virus was uniquely characterized by multiple insertions and deletion mutations in the gene suggesting a potential of causing complex epidemic.