Identification And Characterization Of NDV Isolates From Wild Spotbill Duck

Newcastle disease is defined as an infectious disease of birds caused by a virus of avian paramyxovirus serotype1 (AMPV-1). Since 1997, the goose flocks in some regions of South and East China have experienced severe outbreaks of Newcastle disease virus (NDV) infection. Although measures have been taken to control the disease, it still spreads progressively. In recent years, papers about outbreaks of NDV in other waterfowl and birds are reported, while the characterization of the pathogen is not very clear. Here, we reported the characterization of wild spotbill duck-pathogenic NDV isolates.1 Identification of virulence of NDV isolates from spotbill duckObservation results by transmission electron microscope were found that 3 isolates of wild spotbill duck had typical structure of NDV. IFA with polyclonal antibody specific to NDV conformed that these isolates were NDV. These viruses could kill the chicken embryos, which showed severe pathological changes including bleeding whole body. MDT (Mean Death Time)s of the isolates 7XJS061,8XJS062 and L2JS063 in SPF chicken embryos were 52h,48h,46h, ICPI (Intracerebral Pathogenicity Index) were 1.523 (forL2JS063) and TCID₅₀ were 10^5.625/0.1ml,10^7.25/0.1ml,10^8.625 /0.1ml respectively. These results indicated that the three NDV isolates from wild duck are very virulent viruses. 2 Analysis of the fusion (F) protein gene of NDV isolates from wild spotbill duckTo study the genetic characteristics of these NDV isolates from wild duck, F gene were respectively amplified with RT-PCR, and cloned into T-easy vector and sequenced. F gene sequences analysis results showed that the cracking sequences for the three isolates were ¹¹²R-R-Q-K-R-F¹¹⁷, which was typical sequence for virulent strains of NDV. The sequences of the isolates showed 97.5%-97.6% identities with ZJ1 strain from goose, 84.3%-84.4% identities with FM1 strain from duck, 84.5 % identities with Lasota, 97.5-97.6 % identities with F48E9, 84.5%-84.6% identities with SP13 strain from swine and 98.1%-98.2% identities with Ch983 strain from chicken gene typeâ…¦.3 Analysis of the hemagglutinin-neuraminidase (HN) C-terminal gene of NDV isolates from spotbill duckTo further study the genetic characteristics of these NDV isolates from wild duck, hemagglutinin-neuraminidase (HN) C-terminal genes of these isolates were respectively amplified with RT-PCR, and cloned into T-easy vector and sequenced. The analysis results of HN C-terminal genes sequence showed that the ending code of the three strains was in the same position as F48E8 strain and 18nt shorter than Lasota (avirulent strain). The result also showed that the three NDV isolates from wild duck were virulent strain and indicated that their occurrence might relate with NDV epidemiology in chicken and goose.