Characterization of avian adenovirus type-4 causing hydro-pericardium syndrome in broilers in Karachi, Pakistan

Document Type : Full paper (Original article)


1 Sindh Poultry Vaccine Center, Animal Science Complex, Korangi, Karachi, Pakistan

2 Juma Research Laboratory, Aga Khan University and Hospital, Karachi, Pakistan

3 Department of Physiology, University of Karachi, Karachi, Pakistan


Avian adenovirus was isolated from naturally infected birds during 1990 to 2003 in the vicinity of
Karachi, Pakistan. The virus is known to cause hydro-pericardium syndrome (HPS) in poultry. The mortality
was recorded 20-50% in commercial broilers. Fifty field samples were collected; however, six samples were
selected for molecular studies. These isolates were grown and characterized by cell culture using chicken
embryo liver cell culture, chicken embryo pathogenicity, agar gel precipitation (AGP), serum neutralization
test, DNA extraction, polymerase chain reaction (PCR) and restriction enzyme analysis (REA). Reference
strain J2-A (ATCC VR-829) was used to confirm that HPS isolates belongs to avian adenovirus type-4. The
disease was reproduced in 28-day-old broilers by intramuscular inoculation of cell extracts. Typical hydropericardium was observed in experimental chickens 72 h post-inoculation. The 50% neutralization endpoint of pooled sera of these isolates was not recorded more than 1:40. The results showed that there was no difference in PCR product of 1319 bp with H3/H4 primer on agarose gels, which is characteristic of group 1 avian adenovirus (AA). Restriction fragment length polymorphism (RFLP) analysis of PCR products using restriction enzyme Hpa II resulted in five bands confirming the presence of AA in the analyzed samples.