The isolation and characterisation of astroviruses from chickens.

The isolation, cultivation and characterization of three chicken astroviruses (CAstV) isolates are described. They are antigenically related to each other but unrelated to avian nephritis virus (ANV) and duck hepatitis virus type 2 (DVH2) in neutralization, immunofluorescence and gel diffusion tests. CAstV, ANV and DVH2 all grew well in the LMH cell line, which was used for assay and serological tests. Serological surveys in 1982 and 2001 showed that antibody to CAstV virus was widespread in broiler and broiler breeder flocks and present in some turkey flocks. Infection of 1-day-old specific pathogen free chicks with one isolate in the laboratory resulted in mild diarrhoea and some distention of the small intestine. The virus could be isolated in high titres from all parts of the small intestine but rarely from other organs. Electron microscopic examination of purified particles of this agent revealed the presence of clusters of small round viruses with a diameter ranging from 25 to 30 nm. The amino acid sequence derived from the relatively conserved non-structural polyprotein region of this virus shows 62% identity with the corresponding region of turkey astrovirus 2, 58% identity with turkey astrovirus 1, 55% identity with avian nephritis virus and 33% identity with sheep astroviruses. Taken together, the results indicate that the agent is a new chicken astrovirus belonging to the family Astroviridae.