Molecular and pathological evaluation of a velogenic Newcastle disease virus strain circulating in Vietnam

Newcastle disease virus (NDV) poses a major challenge to poultry farming in Vietnam as it continues to threaten both economic and food security. Despite vaccination efforts, outbreaks caused by velogenic NDV strains continue to occur, indicating gaps in our understanding of the pathogenicity of these viruses. In this study, a velogenic NDV strain (genotype VII.2) was isolated from vaccinated chickens during an outbreak in southern Vietnam. Whole genome sequencing and phylogenetic analyses confirmed that this isolate belongs to a genotype associated with virulent NDV strains. The strain had an intracerebral pathogenicity index (ICPI) of 1.81 and a mean-death-time (MDT) of 56 h. Experimental infection of domestic chickens showed a rapid onset of severe clinical signs, extensive tissue damage, and a high mortality rate, even in co-housed, uninfected chickens. Virus excretion via the oral cavity and cloaca of the experimental chickens facilitated rapid transmission within the flock. These results underscore the urgent need for enhanced epidemiological surveillance and tailored vaccination strategies to mitigate the impact of NDV outbreaks in Vietnam. This study provides important insights into the pathogenicity, transmission, and lesion profile of NDV genotype VII.2, contributing to the development of effective control measures. Velogenic NDV genotype VII.2 detected in vaccinated chickens in southern Vietnam.Isolate was highly virulent with ICPI 1.81 and MDT of 56 h.Rapid onset of disease, severe lesions, and efficient oral/cloacal viral shedding.Findings call for improved NDV surveillance and tailored vaccination in Vietnam. Velogenic NDV genotype VII.2 detected in vaccinated chickens in southern Vietnam. Isolate was highly virulent with ICPI 1.81 and MDT of 56 h. Rapid onset of disease, severe lesions, and efficient oral/cloacal viral shedding. Findings call for improved NDV surveillance and tailored vaccination in Vietnam.

新城疫病毒（Newcastle disease virus, NDV）对越南家禽养殖业构成重大挑战，因其持续威胁当地经济与粮食安全。尽管已实施疫苗接种工作，但由速发型NDV毒株引发的疫情仍时有暴发，反映出当前我们对这类病毒致病性的认知存在缺口。本研究从越南南部某疫情暴发期间的免疫鸡群中，分离获得一株速发型NDV毒株（VII.2基因型）。全基因组测序与系统发育分析证实，该分离株隶属于与强毒NDV毒株相关的基因型。该毒株的脑内致病性指数（intracerebral pathogenicity index, ICPI）为1.81，平均死亡时间（mean-death-time, MDT）为56小时。对家鸡开展的人工感染实验表明，即便与感染鸡同笼的未感染个体，也会快速出现严重临床症状、广泛性组织损伤，并呈现高死亡率。实验鸡只通过口腔与泄殖腔排出病毒，这推动了鸡群内的快速传播。上述结果凸显出加强流行病学监测与定制化疫苗接种策略的紧迫性，以减轻越南NDV疫情造成的影响。本研究为VII.2基因型NDV的致病性、传播特性与病变谱提供了重要见解，可为有效防控手段的开发提供重要支撑。
于越南南部免疫鸡群中检出速发型VII.2基因型NDV。该分离株毒力极强，ICPI值为1.81，MDT为56小时。疾病发病迅速、病变严重，且可通过口腔/泄殖腔高效排出病毒。研究结果呼吁越南加强NDV监测并推行定制化疫苗接种策略。
于越南南部免疫鸡群中检出速发型VII.2基因型NDV。该分离株毒力极强，ICPI值为1.81，MDT为56小时。疾病发病迅速、病变严重，且可通过口腔/泄殖腔高效排出病毒。研究结果呼吁越南加强NDV监测并推行定制化疫苗接种策略。