Outbreaks of hydropericardium syndrome and molecular characterization of Korean fowl adenoviral isolates

Outbreaks ofhydropericardium syndrome (HPS), caused by fowl adenovirus serotype 4 (FAdV-4), have occurred in Korea and caused severe economic loss due to mortality and weight loss. From these outbreaks, several adenoviruses were isolated and identified in samples from broilers, layers, breeders, and native Korean fowl. In pathologic examinations, hydropericardium and multifocal hepatic necrosis, with an intranuclear inclusion body in hepatocytes, were observed. Specific adenovirus particles were also observed in the nucleus of hepatocytes, by electron microscopic examination. Polymerase chain reaction (PCR) analysis of the hexon gene identified all of the isolates as FAdV, serotype 4 and genotype C. To reproduce FAdV-4 field cases, 8- and 52-week-old specific pathogen free (SPF) chicks were infected intramuscularly with the field isolate CBU070244. The mortality rate of infected chicks ranged from 10%-40%, and specific pathologic lesions, such as swollen livers and hydropericardium, were observed. Further studies to determine the prevalence of infection, and analysis of the economic impact to the poultry industry, are needed in the near future.