Molecular Detection, Biological Characterization and Evaluation of Protective Potentiality of a Velogenic Strain of Newcastle Disease Virus Isolate of Bangladesh

Abstract

Aims: The aim of this study was to isolate and characterize Newcastle disease virus (NDV) from recent outbreaks in Bangladesh and protective potentiality evaluation of a velogenic NDV strain. Methodology: A total of 19 lung tissue samples were collected from dead layer chickens of clinically suspected Newcastle disease (ND) cases. Ten days old embryonated chicken eggs, day-old chick and six-week-old sero-negative chickens were used for the isolation and pathotype determination of the virus. Hemagglutination (HA), hemagglutination inhibition (HI) tests using anti-APMV-1 polyclonal serum were used for primary identification and reverse transcription polymerase chain reaction (RT-PCR) was carried out for the confirmation of the isolated viruses by amplification of F gene of NDV using gene specific primers. Three, out of eleven isolates of NDV were subjected to pathotype determination by mean death time (MDT), intracerebral pathogenecity index (ICPI) and intravenous pathogenecity index (IVPI). One of the isolates of NDV of the year 2012 was selected as vaccine candidate to determine its immunogenicity. ND vaccine was prepared by inactivating virulent Newcastle disease virus (vNDV) with 0.1% formaldehyde and adjuvanted with 40% aluminium hydroxide gel. Results: Of the 19 samples total eleven isolates were initially identified as NDV by HA and HI tests and finally confirmed by RT-PCR. Results of MDT, ICPI and IVPI indices indicated that all the isolates of NDV of 2011 and 2012 were velogenic in nature. The inactivated vaccine produced satisfactory level of antibody titre at 72 days of post vaccination and revealed 100% protection during challenge experiment with 2 egg lethal dosage, ELD50/bird against both the velogenic strains of NDV. Conclusion: The frequent outbreaks of ND caused by vNDV in Bangladesh could easily be controlled by using inactivated vaccine prepared with velogenic strain of NDV.