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Subject: Microbiology × Author: AKHILA JOY ×
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    ThesisItemOpen Access
    ISOLATION AND CHARACTERISATION OF INFECTIOUS BURSAL DISEASE VIRUS FROM KERALA
    (COLLEGE OF VETERINARY AND ANIMAL SCIENCES MANNUTHY, THRISSUR, KERALA VETERINARY AND ANIMAL SCIENCES UNIVERSITY, 2022-09-24) AKHILA JOY; Dr. Sreeja R. Nair
    Infectious bursal disease (IBD), caused by the infectious bursal disease virus (IBDV), is one of the top five infectious diseases of poultry that discernibly affects the commercial poultry industry. The mutating viral genome of IBDV accounts for many field outbreaks even after following stringent biosecurity measures. In this study, for the detection of IBDV in Kerala, 51 bursa of Fabricius samples were collected from three to six-week-old chicken, with clinical signs or lesions suggestive of IBD. Reverse transcriptase-polymerase chain reaction (RT PCR) targeting the hypervariableVP2 region detected six positive samples, and one out of six samples was successfully isolated in 10-11 day-old embryonated chicken eggs (ECE) through the chorio-allantoic membrane (CAM) route. The virus isolated in ECE was genetically characterised by targeting the VP1, VP2 and VP3 genes. The sequence analysis revealed that the deduced amino acid sequence of VP1 gene of the isolate was homologous with an attenuated very virulent vaccine strain of Israel, mb and the VP2 gene was homologous with mb and Ventri IBDV plus vaccine strain of India. The analysis of VP3 gene also revealed the similarity of the isolate with vaccine strains except for a single variation S745N in its deduced amino acid sequence. The phylogenetic analysis of the isolate revealed the close relation of the isolate with mb, Ventri IBDV plus and a very virulent strain of Israel, ks. On sequence analysis of amino acids, the characteristic virulent marker amino acid motifs "SWSASGS" and "TDN" were present in the VP2 and VP1, respectively. Hence, the study revealed that the virus isolate has emerged from an attenuated very virulent vaccine strain and the change in virulence of the strain might be due to S745N in the VP3 gene or any change in the VP4 or VP5 gene, which is beyond the scope of the current study. The present study is the first attempt in Kerala in which analysis of the coding sequence of VP1, VP2 and VP3 genes are employed for characterisation.