[Pathogenic Newcastle virus carrier state in congenitally immune chickens].

Five-day-old chickens decendants of hens vaccinated several times under conditions existing in the practice were ophtalmo-nasally inoculated with 10(5),5ELD50 velogenic viscerothropic Newcastle Disease virus NDV. Thirty two per cent of them were stricken by the disease and died, but the remaining 68% resisted the provocation and showed no clinical symptoms 80 days post inoculation. The virulogical investigation of the chickens resistant to inoculation proved they are spreading the virus for 45 days and remained virus-carriers for 54 days post inoculation. NDV did not change its pathogenic properties even after persisting for long periods of time. Two virulogical methods for virus isolation were used -- tissue homogenates and cloaca washings inoculated on hen embryos and tracheal organ culture. The advantages and the great possibilities for discovering latent NDV infection of the organ culture are pointed out. Latent fowl pest infection in birds is discussed.