Avian Reoviruses. III. Infectivity and Egg Transmission

Viruses 24 and 25 did not produce cloacal pasting in day-old chicks inoculated orally under germ-free conditions, although attempts to reproduce cloacal pasting in chicks under isolation conditions were successful but inconsistent. The chicks that had cloacal pasting were depressed, off feed, and showed a loss in weight. The viruses infected the chicks but did not produce cloacal pasting under germ-free conditions. The chicks infected under isolation as well as germ-free condition did have antibody titers against the virus inoculated. Day-old turkey poults showed no clinical signs or lesions after oral inoculation of either reovirus 24 or 25. The viruses could be passed serially on the chorioallantoic membrane of embryonating chicken eggs, where they produced plaques, multiplied to a high concentration, and caused liver necrosis and death of embryos. There was no virus multiplication in either the yolk sac or the allantoic cavity of the embryonating chicken eggs. The viruses produced syncytial type of cytopathogenic effects (CPE) in whole chickenembryo primary cell culture, although they did not multiply to a high concentration. A similar type of CPE was observed in infected chicken-embryo kidney cell cultures. Cytopathogenic effects were not produced in bovine fetal kidney, liver, endocardial, and corneal cell cultures inoculated with these viruses. Plaques approximately 1.5 mm in diameter were produced in whole chicken-embryo primary cell cultures inoculated with reoviruses 24 and 25. Egg-transmission studies indicated that the viruses that play a role in the etiology of cloacal pasting are probably strains of avian reoviruses and are egg-transmitted.