Newcastle disease (ND), caused by virulent Newcastle disease virus (NDV), is a highly contagious disease that has led to tremendous economic losses worldwide. Pigeon paramyxovirus type 1 (PPMV-1) is an antigenic and host variant of NDV. However, limited in-depth studies are available concerning side-by-side comparison of pathogenicity of PPMV-1 and its phylogenetically close NDV both in chickens and pigeons. To this end, two phylogenetically closely related NDV isolates, Kuwait 256 and JS/07/04/Pi from chicken and pigeon respectively were pathotypically and genotypically characterized in this study. The results indicated that Kuwait 256 was a velogenic strain, while JS/07/04/Pi was a mesogenic strain based on the mean death time of chick embryos (MDT) and intracerebral pathogenicity index in 1-day-old chicks (ICPI). Pathogenicity tests showed that Kuwait 256 caused severe clinical signs and 100 % mortality, while JS/07/04/Pi caused no apparent disease in chickens. Interestingly, both Kuwait 256 and JS/07/04/Pi caused morbidity and mortality in pigeons. Notably, pigeons infected with JS/07/04/Pi exhibited viral shedding for longer time compared to Kuwait 256-infected pigeons. Collectively, the findings of this study suggested that PPMV-1 decreased the pathogenicity in chickens but gained a survival advantage over NDV of chicken origin after its adaptive variation in pigeons based on the previous evidence that PPMV-1 originated from chicken-origin viruses. This study laid the foundation for the elucidation of the molecularmechanism underlying difference in pathogenicity of PPMV-1 and chicken-origin NDV in chickens.

由强毒新城疫病毒（NDV）引起的新城疫（ND）是一种高度传染性的疾病，已导致全球范围内的巨大经济损失。鸽子副粘病毒1型（PPMV-1）是NDV的抗原和宿主变异体。但是，有关在鸡和鸽子中PPMV-1及其系统发育上接近的NDV致病性的并排比较的有限的深入研究是可用的。为此，在这项研究中，分别从鸡和鸽子的两个系统发育上密切相关的NDV分离株科威特256和JS / 07/04 / Pi进行了病理分型和基因分型。结果表明，根据雏鸡胚胎的平均死亡时间（MDT）和1日龄雏鸡的脑内致病性指数（ICPI），科威特256是一种致狂毒株，而JS / 07/04 / Pi是致病菌株。致病性测试表明，科威特256引起严重的临床体征和100％的死亡率，而JS / 07/04 / Pi没有引起鸡的明显疾病。有趣的是，科威特256和JS / 07/04 / Pi都造成了鸽子的发病率和死亡率。值得注意的是，与科威特256感染的鸽子相比，被JS / 07/04 / Pi感染的鸽子表现出更长的病毒脱落时间。总的来说，这项研究的结果表明，PPMV-1降低了鸡的致病性，但在鸽子适应性变异后，PPMV-1较鸡源的NDV获得了生存优势，这是基于先前的证据表明PPMV-1源自鸡源病毒。该研究为阐明PPMV-1和鸡源NDV致病性差异的分子机制奠定了基础。