Detection and transmission of 30 nm virus particles (astroviruses) in faeces of lambs with diarrhoea.

An outbreak of diarrhoea in lambs was investigated, and electron microscopic examination revealed small round virus-like particles in the faeces from eight of seventeen lambs. A bacteria-free filtrate of faeces from one lamb was given orally to a gnotobiotic lamb, which subsequently excreted virus in faeces. Intestinal contents were collected from this lamb and a filtrate given orally to two further gnotobiotic lambs, which subsequently developed diarrhoea and excreted virus in faeces. The mean diameter of the virus particles was 29.7 nm, and 12 per cent of them showed their surface structure arranged in the form of a six-pointed or five-pointed star. They were similar to those particles previously observed in human infant faeces which were referred to as "astroviruses". The passage through gnotobiotic lambs with development of diarrhoea showed that these particles were animal viruses which were probably pathogenic for lambs.