Alazawy Amer Khazaal, Al Ajeeli Karim Sadun
Department of Microbiology, College of Veterinary Medicine, University of Diyala, Diyala, Iraq.
Vet World. 2020 Jan;13(1):33-39. doi: 10.14202/vetworld.2020.33-39. Epub 2020 Jan 4.
Newcastle disease virus (NDV) remains a major viral disease of poultry. The morbidity and mortality rates of chickens vaccinated with NDV in broiler farms in Diyala Province were 100% and 80%, respectively, rates due to suspected infection with the highly virulent NDV. The present study aimed to isolate and identify the NDV virus and evaluate its pathogenicity in infected broiler chickens at poultry farms.
Broiler chickens at two commercial poultry farms were suspected of being infected with virulent NDV due to high mortality rates. Virus isolated from samples of intestinal tissues, lungs, trachea, spleen, kidneys, and air sacs was adapted in the allantoic cavity of embryonated specific-pathogen-free (SPF) chicken eggs. The NDV pathotype was determined based on the mean death time (MDT) in eggs as well as the intracerebral pathogenicity index (ICPI) and intravenous pathogenicity index pathogenicity indexes of the isolated samples. Broilers were experimentally infected by inoculation with fluids collected from the allantoic cavities of 60 broilers aged 35 days. Serological and molecular tests were followed by enzyme-linked immunosorbent assay to determine levels of anti-NDV immunoglobulin G, and isolates were identified using a hyperimmune (HI) test and real-time polymerase chain reaction (RT-PCR).
Suspected and isolated NDV field samples propagated in the allantoic cavity of 10-day-old fertile SPF chickens were NDV positive in the rapid hemagglutination test within a few seconds. Pathogenicity indices and MDT showed that the isolated NDV was viscerotropic and velogenic. The virus was identified as NDV by the HI test using specific anti-LaSota HI serum and RT-PCR with specific primers and probes. Propagation of the virus in the allantoic cavity of embryonated hen eggs produced a viral titer of 10 EID/0.1 mL.
The virus isolated from broiler chicken farms in Diyala Province, Iraq, was viscerotropic and velogenic according to the pathogenicity indices and RT-PCR. The isolated NDV caused 100% morbidity and 90% mortality in NDV-vaccinated and experimentally infected broiler chickens.
新城疫病毒（NDV）仍是家禽的一种主要病毒性疾病。迪亚拉省肉鸡养殖场中接种了新城疫病毒疫苗的鸡的发病率和死亡率分别为100%和80%，这是疑似感染高致病性新城疫病毒所致。本研究旨在分离和鉴定新城疫病毒，并评估其在家禽养殖场感染肉鸡后的致病性。
两个商业家禽养殖场的肉鸡因死亡率高而疑似感染了强毒新城疫病毒。从肠道组织、肺、气管、脾脏、肾脏和气囊样本中分离出的病毒在无特定病原体（SPF）的鸡胚尿囊腔中传代培养。根据病毒在鸡胚中的平均死亡时间（MDT）以及分离样本的脑内致病性指数（ICPI）和静脉致病性指数来确定新城疫病毒的致病型。通过接种从60只35日龄肉鸡的尿囊腔中收集的液体对肉鸡进行实验性感染。血清学和分子检测之后进行酶联免疫吸附测定以确定抗新城疫病毒免疫球蛋白G的水平，并使用血凝抑制（HI）试验和实时聚合酶链反应（RT-PCR）对分离株进行鉴定。
在10日龄有活力的SPF鸡胚尿囊腔中传代培养的疑似和分离的新城疫病毒野外样本在快速血凝试验中几秒钟内呈新城疫病毒阳性。致病性指数和MDT表明分离出的新城疫病毒是嗜内脏速发型的。使用特异性抗LaSota HI血清通过HI试验以及使用特异性引物和探针通过RT-PCR将该病毒鉴定为新城疫病毒。该病毒在鸡胚尿囊腔中的传代培养产生了10 EID/0.1 mL的病毒滴度。
根据致病性指数和RT-PCR，从伊拉克迪亚拉省肉鸡养殖场分离出的病毒是嗜内脏速发型的。分离出的新城疫病毒在接种了新城疫病毒疫苗并经实验感染的肉鸡中引起了100%的发病率和90%的死亡率。
