CHARACTERISATION OF NEWCASTLE DISEASE VIRUS ISOLATES PREVALENT IN KERALA
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Date
2021-12-30
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES MANNUTHY, THRISSUR
Abstract
Newcastle disease caused by Newcastle disease virus (NDV) is one of the
highly pathogenic viral diseases of poultry and is considered to cripple poultry
industry globally. The diagnosis of the disease is based on virus isolation and
characterisation and detection of the genome of the virus by molecular techniques
such as reverse transcriptase polymerase chain reaction (RT-PCR). Samples collected
from dead and ailing birds showing lesions and signs suggestive of ND formed the
materials for the study. Out of the 63 samples collected, eight revealed the virus in
RT-PCR targeting the F gene, directly from the tissue samples. The NDV could be
isolated in embryonated chicken eggs from the samples which yielded positive
amplicons by RT-PCR. All the viral isolates showed haemagglutination activity (4 to
10 log₂) and was inhibited by the NDV specific antiserum. The HI titre for all the
isolates was found to be 4 log₂. The ICPI and MDT indices were determined. The
ICPI values were in between 0.75 to 1.53 and MDT values varied from 54 h. to 79.2
h. Based on the intracerebral pathogenicity index and mean death time, three of the
isolates were classified under velogenic group and the remaining five under
mesogenic group. The RT-PCR assay targeting the fusion protein cleavage site of the
F gene was carried out and the specific amplified products were sequenced and
phylogenetically analysed. All the isolates were of similar sequences and contained
¹¹²GRQGRL¹¹⁷ monobasic amino acid motifs at FPCS region, which is peculiar to
lentogenic viruses. On phylogenetic analysis, all the isolates were grouped in
genotype II of class II viruses. In this study, NDV isolates with lentogenic FPCS
region belonging to velogenic and mesogenic pathotypes were obtained.
Description
Submitted in partial fulfilment of the requirement for the degree of
MASTER OF VETERINARY SCIENCE in Veterinary Microbiology