Asian Research Thesis Index

Abstract

Poultry diseases are a matter of serious concern and responsible for extremely large profit
making crisis in poultry industry per anum. Outbreaks of infectious bursal disease (IBD) are
continuously increasing despite vaccination in commercial broilers. The strains of IBDV
currently circulating in Chakwal district broiler flocks are not known. Clinicopathologic
analysis and reverse transcriptase PCR were used in 18 poultry farms which were situated in
district Chakwal to confirm field outbreaks of IBD. The genetic analysis of the hypervariable
part of the?VP2?gene was utilized to describe different features of total 6 isolates of these
outbreaks. Arrangement of nucleotides, infer amino acid sequences through phylogenetic
analysis of VP2 gene containing hypervariable part were used for dividing IBDV strains into
two groups. According to phylogenetic analysis, 5 IBDV strains showed special signatures of
amino acid in the VP2 gene as A222, I242, I256, I294, S299 and classified as vvIBDV.They
showed 97%?99% identity at the nucleotide level. Furthermore, the sequencing analysis of
detected field strains revealed the high similarity and close clustering with vvIBDV strains
isolated from India, Pakistan, and China, suggesting geographic and temporal relationships
among these strains. Interestingly, one IBDV strain clustered togather with vaccinal IBDV
strains and representing 99% sequence likeness with vaccine strains which were dissipated,
suggesting possible role of attenuated vaccines in the outbreaks of IBD. Our study revealed
circulation of vvIBDV strains in Chakwal broiler flocks and these evidences emphasize the
need of further detailed and more systemic approaches to evaluate IBDV diffusion and
characterization to design effective control strategies.

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