[Study of the pathogenic qualities of 4 celo-virus strains isolated in Bulgaria]

Four CELO virus strains, isolated in this country, were used to infect 3-day-old chicks via the trachea, muscularly, orally, subcutaneously, and cerebrally. The chicks were killed on the 2nd, 4th, 6th, 9th and 16th day following inoculation. Material was taken from each chick for morphologic, virologic, and serologic examination. The clinical course of the disease was also followed up. Prior to killing some birds showed infirmity, difficult breathing, slightly expressed diarrhia, going off food, and more sporadically there was fecal mass around the cloaca matting the plumage. Some manifested nervous symptoms similar to those observed in cases of Newcastle disease and encephalitis of birds. In some of the chicks there were hyperemia of the lungs, trachea, and intestins as well as necrotic foci in the liver.