Molecular characterization and phylogenetic analysis of fowl adenoviruses isolated from commercial poultry flocks in Pakistan during 2014-15

Abstract

Fowl adenovirus has been reported in many countries and is a contagious agent related with inclusion body hepatitis (IBH) and hydropericardium syndrome (HPS) in chickens worldwide. Identification of fowl adenovirus (FAdV) serotype is of most importance in epidemiological studies of disease outbreak and the adaptation of vaccine strategies. In spite of appropriate administration of vaccination, FAdV outbreaks have been reported and caused significant losses in poultry flocks throughout Pakistan in recent years. To identify the serotype and gain a better understanding of the genetic properties of the FAdV strains responsible for recent outbreaks, the sequence analysis of hexon gene of 10 isolates associated with IBH and HPS was determined. Sequence alignment and phylogenetic analysis based on direct sequencing of hypervariable region of hexon gene grouped these sequences into two distinct groups, three FAdV isolates were clustered together belonging to fowl adenoviruses C species and serotype FAdV-4. The similar viruses have been commonly isolated since late 1980s from the poultry flocks. In addition, seven genetically related FAdV isolates were from fowl adenovirus type 11 in D species. To our knowledge, this is the first report of FAdV-11 strains identified in poultry production facilities in Pakistan. This study reveals the presence of two distinct groups of FAdV-4 and FAdV-11 in chickens affected with hydropericardium syndrome and inclusion body hepatitis. To control FAdvs, strict biosecurity protection measures are necessary and we propose the continuous epidemiological surveillance to support the prevention of the viruses spread into non-epidemic areas.