Guy J S, Barnes H J, Smith L
Department of Microbiology, Pathology, and Parasitology, College of Veterinary Medicine, North Carolina State University, Raleigh 27606.
Avian Dis. 1991 Apr-Jun;35(2):348-55.
Modified-live (ML) infectious laryngotracheitis (ILT) vaccine viruses, both tissue-culture-origin (TCO) and chicken-embryo-origin (CEO), were passaged 20 times in specific-pathogen-free chickens. After serial bird-to-bird passage, increased virulence was observed for CEO virus but not TCO virus. Increased mortality and increased severity and duration of respiratory disease were observed in chickens inoculated with chicken-passaged CEO viruses; only mild respiratory disease (no mortality) occurred in chickens inoculated with chicken-passaged TCO viruses. These findings suggest that ML ILT vaccine viruses may increase in virulence after bird-to-bird passage.
改良活（ML）传染性喉气管炎（ILT）疫苗病毒，包括组织培养源（TCO）和鸡胚源（CEO），在无特定病原体的鸡中传代20次。经过连续的鸡对鸡传代后，观察到CEO病毒的毒力增加，而TCO病毒则没有。在用鸡传代的CEO病毒接种的鸡中观察到死亡率增加以及呼吸道疾病的严重程度和持续时间增加；在用鸡传代的TCO病毒接种的鸡中仅出现轻度呼吸道疾病（无死亡）。这些发现表明，ML ILT疫苗病毒在鸡对鸡传代后可能毒力增加。
