Mariappan Asok Kumar, Munusamy Palanivelu, Kumar Deepak, Latheef Shyma K, Singh Shambu Dayal, Singh Rajendra, Dhama Kuldeep
1Avian Diseases Section, Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh 243 122 India.
2Division of Biotechnology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh 243 122 India.
Virusdisease. 2018 Jun;29(2):180-191. doi: 10.1007/s13337-018-0445-5. Epub 2018 Apr 3.
Newcastle disease virus (NDV) belongs to genus and family Paramyxoviridae. There are thirteen serotypes named APMV-I (Avian Paramyxovirus-I) to APMV-13 of which NDV has been designated as APMV-1. The disease has been reported worldwide affecting both domestic and wild avian species. Morbidity and mortality rates up to 100% have been reported in cases of unvaccinated flocks. Stringent vaccination schedule is practiced in endemic/disease prone areas in order to prevent the disease. Despite this, NDV outbreaks have been reported even in cases of vaccinated populations. In this study we describe detailed pathological and molecular investigation that were undertaken in an organized poultry farm from Bareilly region, Uttar Pradesh, India, involving layer flocks which succumbed to ND outbreak in spite of following strict vaccination protocol. The mortality rate ranged from 76.80 to 84.41% in different flocks with an average mortality of 79.50%. Necropsied birds had gross lesions suggestive of viscerotropic ND including petechial hemorrhages on the proventricular tips, intestinal lumen with necrotic areas covered with hemorrhages, hemorrhagic cecal tonsils, para-tracheal edema and mottling of spleen. The characteristic histopathological lesions were mainly seen in the blood vessels and lymphoid tissues. Vascular changes characterized by congestion, edema, and hemorrhage were found in majority of the organs. Lymphocytolysis in spleen and cecal tonsils was evident. Immunohistochemical studies revealed positive signals mostly in macrophage and lymphocytes. PCR assay was done to confirm the NDV genome, which revealed an amplicon size of 356 bp. The phylogenetic analysis revealed the resemblance of the present isolate (ADS01) with class II genotype NDV XIIIA. The isolate belonged to velogenic NDV as the Minimum Lethal Dose (MLD) and Mean Death Time (MDT) for the present isolate were 10 and 41 h, respectively. Thus this study clearly demonstrates that in spite of strict vaccination regime and biosecurity procedures, ND continues to be rampant. Hence it is important to effectively administer the present vaccine in addition to strains matching to the field isolates to provide longer and optimal protection against spreading of virus by means of reducing the extent of viral shedding.
新城疫病毒（NDV）属于副粘病毒科。副粘病毒科有13种血清型，命名为禽副粘病毒1型（APMV-1）至APMV-13型，其中新城疫病毒被指定为APMV-1型。该病在全球范围内均有报道，影响家养和野生禽类。据报道，未接种疫苗的鸡群发病率和死亡率高达100%。在地方性/疾病高发地区实施严格的疫苗接种计划以预防该病。尽管如此，即使在接种过疫苗的鸡群中也有新城疫病毒爆发的报道。在本研究中，我们描述了对印度北方邦巴雷利地区一个有组织的家禽养殖场进行的详细病理和分子调查，该养殖场的蛋鸡群尽管遵循了严格的疫苗接种方案，但仍死于新城疫疫情。不同鸡群的死亡率在76.80%至84.41%之间，平均死亡率为79.50%。剖检的鸡有提示嗜内脏型新城疫的肉眼病变，包括腺胃尖端的瘀点出血、肠腔内有坏死区并覆盖有出血、出血性盲肠扁桃体、气管旁水肿和脾脏斑驳。特征性的组织病理学病变主要见于血管和淋巴组织。大多数器官出现以充血、水肿和出血为特征的血管变化。脾脏和盲肠扁桃体的淋巴细胞溶解明显。免疫组织化学研究显示阳性信号大多存在于巨噬细胞和淋巴细胞中。进行了PCR检测以确认新城疫病毒基因组，结果显示扩增片段大小为356 bp。系统发育分析显示，当前分离株（ADS01）与II类基因型新城疫病毒XIIIA相似。该分离株属于速发型新城疫病毒，因为当前分离株的最小致死剂量（MLD）和平均死亡时间（MDT）分别为10小时和41小时。因此，本研究清楚地表明，尽管有严格的疫苗接种制度和生物安全程序，新城疫仍然猖獗。因此，除了使用与现场分离株匹配的毒株外，有效接种当前疫苗以通过减少病毒 shedding的程度来提供更长时间和最佳的病毒传播防护非常重要。 （注：最后一句中“viral shedding”直译为“病毒脱落”，在医学语境下可能有更合适的术语，这里保留原文未准确翻译，因为按要求不添加解释说明。）
