Experimental studies on the aetiology of inclusion body hepatitis

Liver suspensions and an adenovirus isolated from typical cases of inclusion body hepatitis (IBH) were inoculated into specific pathogen free birds by a combined oral and intranasal route but no pathological changes resulted. Representative strains of 8 serotypes of avian adenoviruses from naturally occurring cases of IBH and non-hepatitis origins were inoculated intramuscularly into birds. The pathogenicity of these strains was studied and it was established that different strains produced different lesions; thus a diffuse and generalised hepatitis, diffuse and patchy hepatitis, focal hepatitis or no pathological changes were observed. In no instance were the lesions produced identical to those in natural outbreaks of IBH. Extra-hepatic haemorrhages were not seen in experimental birds and the inclusion bodies in their livers were consistently basophilic. Eosinophilic inclusion bodies, as seen in natural cases, were not identified in adenovirus-infected birds. Intramuscular inoculation of a reovirus isolated from a clinical case of IBH failed to induce liver lesions in birds and adenoviruses isolated from turkeys and adenoviruses and herpesvirus isolated from pigeons were also unsuccessful at producing hepatitis in fowl.