The present invention includes isolated astroviruses capable of reproducing the full Runting Stunting Syndrome (RSS) disease spectrum in poultry, including a chicken astrovirus isolated from the gut of chickens (CkAstV-Gut), a cell culture chicken astrovirus CkAstV-p5, and a chicken astrovirus isolated after back passage in chicken (CkAstV-p5-Ckp5), and infected cell lines, cell culture supernatants, polynucleotide sequences, vectors, polypeptides, compositions, and vaccines thereof. The present invention also includes diagnostic methods based on such isolated viruses and infected cell lines, cell culture supernatants, polynucleotide sequences, vectors, and polypeptides thereof, and methods of protecting poultry, including chickens, against RSS by the administration of such isolated viruses and infected cell lines, cell culture supernatants, polynucleotide sequences, vectors, polypeptides, compositions, and vaccines thereof.
