Pathogenicity and molecular characterization of a fowl adenovirus 4 isolated from chicken associated with IBH and HPS in China

Limin Li,Shan Zhang,Jiguo Sun,Ping Chen,Jianchang Wang,Wanzhe Yuan

doi:10.1186/s12917-018-1733-4

Abstract

BackgroundSince July in 2015, an emerging infectious disease, Fowl adenovirus (FAdV) species C infection with Hepatitis-Hydropericardium syndrome was prevalent in chicken flocks in China. In our study, one FAdV strain was isolated from commercial broiler chickens and was designated as SDSX1.The phylogenetic information, genetic mutations and pathogenicity of SDSX1 were evaluated.ResultsThe phylogenetic analysis indicated that SDSX1 is a strain of serotype 4, FAdV-C. The amino acid analysis of fiber-2 showed that there were more than 20 mutations compared with the non-virulent FAdV-C strains. The pathogenic evaluation of SDSX1 showed that the mortality of one-day-old chickens inoculated SDSX1 was 100%. The typical histopathological changes of SDSX1 were characterized by the presence of basophilic intranuclear inclusion bodies in hepatocytes. The virus copies in different tissues varied from107 to 1011 per 100 mg tissue and liver had the highest virus genome copies.ConclusionIn conclusion, the isolate SDSX1, identified as FAdV-4, could cause one-day-old chicks’ typical inclusion body hepatitis (IBH) and hepatitis-hydropericardium syndrome (HHS) with 100% mortality. The virus genome loads were the highest in the liver. Molecular analysis indicated that substitutions in fiber-2 proteins may contribute to the pathogenicity of SDSX1.

Highlights

Since July in 2015, an emerging infectious disease, Fowl adenovirus (FAdV) species C infection with Hepatitis-Hydropericardium syndrome was prevalent in chicken flocks in China
Sequence analysis The virus was isolated from the specific pathogen free (SPF) chicken’s embryos by 5 blind passages and it was designated as SDSX1
According to the phylogenetic analysis based on the full genome (Fig. 1a), the SDSX1 isolate was classified into serotype 4 of FAdV-C

Summary

Introduction

Since July in 2015, an emerging infectious disease, Fowl adenovirus (FAdV) species C infection with Hepatitis-Hydropericardium syndrome was prevalent in chicken flocks in China. The virion capsid consists of three major structural proteins, hexon, fiber and penton base proteins. Hexon is the major protein of the adenovirus capsid known to FAdVs are grouped into 5 species (FAdV-A to FAdV-E) based on genomic restriction enzyme digest patterns with 12 serotypes identified so far: FAdV-A (serotype FAdV-1); FAdV-B (serotype FAdV-5);FAdV-C (serotypes FAdV-4 and -10); FAdV-D (serotypes FAdV-2, − 3, − 9, and − 11); and FAdV-E (serotypes FAdV-6, − 7, −8a, and -8b) [6]. FAdVs infection (the strain was closely related to serotype 11 and 8a) was first reported in Morocco recently [12]. All 12 serotypes of FAdVs have been associated with the outbreak of inclusion body hepatitis (IBH) with a ~ 10% mortality rate

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