The first whole genome sequence and pathogenicity characterization of a fowl adenovirus 4 isolated from ducks associated with inclusion body hepatitis and hydropericardium syndrome

Abstract

In June 2015, an infectious disease with high prevalence causing severe hydropericardium syndrome (HPS) first appeared in duck farms of northeast China. The disease showed high morbidity of 35% and mortality of 15% in a commercial duck farm with 200,000 45-day-old ducks. One strain of hypervirulent fowl adenovirus serotype 4 was identified and designated as HLJDAd15. The whole genome of the duck isolate was sequenced and found to contain the same large deletions as a genotype that has become prevalent in chickens in China recently, indicating that this disease might be transmitted from chickens to ducks. The pathogenicity of HLJDAd15 was evaluated in SPF chickens and ducks. The results showed that chickens were more susceptible to this new genotype of fowl adenovirus, and it was more difficult to infect ducks than chickens with the duck origin virus. Thus, it appears that this severe HPS in ducks is far more likely to have been transmitted from chickens to ducks than from ducks to ducks. Therefore, transmission from chickens to ducks constitutes a threat to the duck farming industry, and this transmission route is a very important consideration for the prevention and control of the new genotype of fowl adenovirus. This is the first whole genome sequence of a FAdV-4 isolated from ducks, and this information is important for understanding the molecular characteristics and evolution of aviadenoviruses. The potential risks of infection with this new hypervirulent FAdV-4 genotype in chickens and ducks urgently require an effective vaccine.

Different Dynamic Distribution in Chickens and Ducks of the Hypervirulent, Novel Genotype Fowl Adenovirus Serotype 4 Recently Emerged in China

“…HHS appears with high frequency in chickens, particularly in broilers, with a mortality that ranges from 10 to 100% (Vera-Hernández et al, 2016; Pan et al, in press). However, the disease has rarely emerged in other hosts with severe clinical signs and high mortality.…”

The Natural Large Genomic Deletion Is Unrelated to the Increased Virulence of the Novel Genotype Fowl Adenovirus 4 Recently Emerged in China

“…The similarity of the hexon sequence between the novel genotype FAdV-4 and each of the other FAdV-4 strains and other species of FAdVs was varied from 98.6–100% and 50.1–76.2%, respectively. The complete genome sequences of HLJFAd15 from layers and HLJDAd15 from ducks (identified as the novel genotype FAdV-4) were submitted to GenBank during our previous study [ 17 , 18 ]. The large genomic deletion 1966Del, located between ORF42 and 43, was sequenced and its absence confirmed in all of the other 15 clinical strains from chickens with emerged HHS, but did not appear in KR5 (HE608152) and ON1 (GU188428) isolated outside of China.…”

“…KU991797) and HLJDAd15 (GenBank no. KX538980) were isolated from layers and ducks, respectively, in our previous studies and shown to be highly virulent strains [ 17 , 18 ]. The remaining 15 clinical isolates were all from chickens with severe HHS from different provinces in China ( Table 1 ).…”

“…All data are shown as the means ± SD of three independent experiments. Furthermore, the third-passage viral cultures of the rescued viruses were harvested and subjected to genomic sequencing following a previously reported method [ 18 ].…”

“…The complete genomes were sequenced and aligned (GenBank Nos. KU991797 and KX538980) [ 17 , 18 ]. A significant natural large genomic deletion (1966 bp) was presented between open reading frames (ORF) 42 and 43 compared with the non-pathogenic strains ON1 (GenBank no.…”