Identification and characterization of an avian adenovirus isolated from a 'spiking mortality syndrome' field outbreak in broilers on the Delmarva Peninsula, USA

A fowl adenovirus isolated from a 'spiking mortality syndrome' field outbreak in broilers on the Delmarva Peninsula, USA, was identified by cross-neutralization tests and by restriction enzyme analysis using eight restriction enzymes as a strain of the fowl adenovirus serotype FAV12. The isolate is nearly identical to strain UF71 though it shows substantially higher virulence in vivo than UF71. Contrary to strains of other fowl adenovirus serotypes (except serotype FAV1), the isolate caused high embryo mortality in specific pathogen free (SPF) chicken embryos inoculated via the allantoic cavity. Infection of 83 one-day-old SPF chicks with 10(5) plaque forming units of the isolate via a natural route led to clinical signs and growth inhibition. Gross and histological lesions in the liver, bursa of Fabricius and thymus, and in five cases hydropericarditis were observed. An inclusion body hepatitis was found in two chicks.